Renewable Energy Communities (RECs): European and Worldwide Distribution, Different Technologies, Management, and Modeling
Department of Industrial Engineering, University of Rome Tor Vergata, 00133 Rome, Italy
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Author to whom correspondence should be addressed.
Energies 2025, 18(15), 3961; https://doi.org/10.3390/en18153961
Submission received: 25 June 2025
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Revised: 17 July 2025
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Accepted: 21 July 2025
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Published: 24 July 2025
(This article belongs to the Section B: Energy and Environment)
Abstract
Renewable energy communities (RECs) are increasingly recognized as pivotal instruments in the global energy transition, offering decentralized, participatory, and sustainable solutions for energy management, specifically regarding energy production and consumption. The present review provides a comprehensive examination of the REC concept, tracing its regulatory evolution, particularly within the European Union through the renewable energy directives (RED II and RED III) and by analyzing its practical implementation across various countries. This paper explores the diverse technologies integrated into REC projects, such as photovoltaic systems, wind turbines, biogas, hydroelectric, and storage solutions, while also considering the socioeconomic frameworks, management models, and local engagement strategies that underpin their success. Key case studies from Europe, Asia, Africa, and Australia illustrate the various approaches, challenges, and outcomes of REC initiatives in different geographic and policy contexts. The analysis also highlights barriers to implementing RECs, including regulatory uncertainty and market integration issues, and identifies the best practices and policies that support REC scalability. By synthesizing current trends and lessons learned, this review aims to inform policymakers, researchers, and practitioners about the transformative role of RECs in achieving decarbonization goals and accomplishing resilient energy systems.
1. Introduction
Renewable energy communities (RECs) represent an innovative model for energy production, consumption, and sharing, promoting a transition toward more sustainable, decentralized, and participatory energy systems. Public or private entities constitute RECs in various forms, following the regulations of the countries in which they operate. They can take the form of cooperatives, registered or unregistered associations, or non-profit legal entities. REC members may include small and medium-sized enterprises (SMEs), local authorities, and groups of individuals, such as public, private, or corporate entities (e.g., condominiums) [1]. They cooperate to produce and consume renewable energy, thereby lowering the environmental impact, reducing energy bill costs, and guaranteeing a return on investment in renewable energy plants. The regulatory evolution of the European Union has played a crucial role in its promotion, in particular through Directive 2009/28/EC [2], which is known as the renewable energy directive (RED I), and the subsequent Directive (EU) 2018/2001. The amended version of RED II, Directive (EU) 2018, and RED III, Directive (EU) 2024/1711, entered into force in 2019 and 2024, respectively [3]. RED I laid the foundations for the diffusion of renewable energies, setting binding targets for Member States to increase the share of energy produced from renewable sources. RED II, which was adopted in 2018, set a binding renewable energy target of at least 32% for the EU by 2030. RED III aimed to increase renewable energy targets for the EU by 2030. RED III, officially referred to as Directive (EU) 2023/2413, aims to ramp up renewable energy use across all sectors in the EU, with a target of at least 42.5% by 2030. It also lays out some ambitious targets for renewable energy in transport, aiming for a minimum of 29% of all energy consumed in this sector to come from renewable sources. Member States are required to incorporate this directive into their national laws by 21 May 2025. However, the first directive did not provide a clear regulatory framework for energy communities, focusing mainly on incentives for renewable production and the simplification of administrative procedures. Despite this, it represented a fundamental starting point for promoting distributed generation and encouraging the active participation of citizens in the energy market. Regarding RECs and the low carbon policies of local regional government support, research tries to answer the question “how can national and regional authorities contribute to implementing local low carbon energy initiatives (LLCEIs)?” Two Dutch case studies in two agricultural scenarios evaluated how to manage the LLCEI experimentation proposed, which was implemented through institutional adaptation and policy innovation, to support the initiatives of the two provinces to incentivize LLCEI. Therefore, in the Netherlands, studies using case examples from two agricultural regions and the Fryslân province explore how national and regional authorities can support LLCEIs by fostering institutional adaptation, policy innovation, and intermediary support to overcome structural barriers, enhance citizen participation, and improve the scalability and acceptance of decentralized, community-driven energy solutions [4,5].
This paper provides a thorough examination of each aspect of RECs, addressing knowledge gaps in RECs, RED II, and RED III, including concepts, implementations, and case studies in the EU and globally. Here is how this paper is structured: Section 2 defines the REC distribution in Europe and around the globe under RED II in detail. Section 3 looks into the covered technologies. Section 4 deepens the REC procedures and applications. Section 5 lists the review articles identified in this study about RECs. Section 6 is all about the roles, activities, and purposes of RECs, while Section 7 discusses the special REC configuration and applications; in Section 8 we provided the discussion and explored the future directions, and, lastly, Section 9 concludes this review.
We examined the literature from 2017 to 2025 by country, technology, research focus, and the types of storage systems used. We have listed the summary of all the analyzed research articles in Table A1, which is found in Appendix A.
There are currently few in-depth review articles that comprehensively address RECs in alignment with RED II, the progress made in Italy, or the involvement of non-European countries. The existing literature often falls short in examining some key aspects such as the actual implementation of RECs across different national contexts, the general and technical barriers that hinder their development, the policy frameworks supporting or constraining them, the role of policymakers, levels of public awareness, and strategies for scaling up REC initiatives. These gaps highlight the pressing need for a detailed and up-to-date review.
In response to this need, the present review provides a comprehensive and structured synthesis of the academic and updated literature on RECs. It explores the foundational concepts, scope, benefits, activities, and current state of development of RECs while also identifying the main challenges and offering practical recommendations for future actions. A specific focus is on the regulatory evolution of RECs, particularly through RED II and RED III in the European Union, and their practical realization in diverse geographical and policy contexts. Unlike earlier reviews, which are often centered on theoretical frameworks or specific case studies, this work introduces a structured classification of REC experiences by country, technology used, and type of contribution (e.g., governance models, techno-economic analyses, real-world implementations). This approach not only reveals the variety of strategies adopted worldwide but also highlights patterns, best practices, and everyday obstacles.
The motivation behind this work is rooted in the growing importance of RECs as actors of the transition to sustainable, decentralized, and community-driven energy systems driven by social and environmental concerns, legislative incentives, and the need to combat energy poverty and improve equity. This paper aims to serve as a valuable reference for researchers, policymakers, practitioners, and community members seeking to understand and strengthen REC initiatives.
We focus this review on the technical, regulatory, and operational dimensions of renewable energy communities while also suggesting the economic impacts at the national level as a direction for future research.
2. REC Distribution in Europe and Around the Globe
The renewable energy communities, RECs, are pivotal in Europe’s energy transition towards a green and sustainable future, attracting private investors, gaining public and community support for green energy initiatives, and facilitating long-term renewable energy source (RES) utilization. The concept of RECs and their implementation can be initiated by examining existing structures and gaps by RED II and RED III in Europe, followed by an analysis of the status and scenarios in other continents, including America, Australia, Africa, and Asia.
2.1. Europe
The study in [6] makes a comparison among the regulatory rules of Europe, Australia, and New Zealand based on a model of the energy market, as well as the relative importance of RESs. In the EU, thanks to RECs, the aim is to make active prosumers responsible and accept the energy transition and to promote investments in this regard. The EU promotes investments in the energy transition by involving prosumers through RECs, encouraging them to act responsibly and actively participate in the transition process. In 2016, in the EU, RES production was 960 TWh, with hydropower taking 37% (10% more than 2006), solar taking 11.6%, and wind taking 31.8% (44 times and 3.7 times as much as in 2006). The most efficient countries are Austria and Sweden, while the least efficient are Cyprus, Hungary, Luxembourg, and Malta. Political actions, economic incentives, and legal initiatives favor the development of RESs. Also, the Directives of the Electricity Authority act in the direction of promoting renewables. The Clean Energy for all Europeans Directive (Directive 2016/11) establishes three key pillars: improving energy efficiency, leading in renewable energy, and ensuring a fair deal for consumers. Within this framework, the EU defines and emphasizes the role of RECs as essential to the energy transition. It codifies RECs in European legislation by specifying their legal form, non-exclusivity, objectives, areas of activity, participation requirements, methods of association, governance models, rights and obligations, procedural rules, roles as system operators, and access to the electricity grid. The idea of renewables comes from German, Dutch, and Danish legislation, and the traditional concept of cooperation inspires it. RECs can be producers, consumers, stores, and sellers of energy; members include private individuals; micro-, small, and medium-sized enterprises; and local authorities; they must be non-profit and based on equality and broad participation. The EU gives its Member States the task of promoting and supporting RECs.
At the European level, access to RECs is essential, but it is only the first step. The second consists of updating the directives that establish the rules of the electricity market. That is the reason why the European REC model is difficult to export. Future trends foresee more space for consumers and their energy structures. The European REC model can be a good starting point to strengthen the European position on this matter. The European REC model [6] is behind the Australian and New Zealand ones, and trusts and cooperatives have more space. Therefore, the European REC model can serve as a good starting point to strengthen the European position on the subject, even though it is difficult to export.
The EU, through the “clean energy package (CEP),” officially recognizes RECs and clearly defines concepts such as self-consumption, collective consumption, electricity sale, and energy sharing. The CEP also analyzes the implications for consumer rights and protections. It examines the role that RECs can have in the flexibility of the market and network operators. It outlines the ownership, operation, and management of electricity networks. RECs and citizen energy communities (CECs) are important means of involving citizens in energy issues [7]. In [8], the authors report the actions that EU Member States have implemented to support the development of RECs. At the EU level, the actions include issuing directives that establish a legal framework to support and promote RECs, which individual Member States then implement.
In [9], the authors present a complete guide to RECs after RED II, which aims to answer the following questions: What are RECs/CECs? How are they defined? Which activities should they be involved with? How should they be regulated? And how should RECs be supported? An analysis of related legal rules is also reported, together with examples from all EU Member States. It contains a study of how to implement the CEP directive and RED II. Also, they report the best practices for implementing RECs. Standard features between RECs and CECs include being voluntary and controlled by members, and they are primarily aimed at providing social, economic, and environmental benefits to members. Different features include different types of members, geographical limits (RECs must be closer), and governance (RECs are more autonomous). It is up to the Member States to define the geographic proximity; e.g., in Italy, it is dependent on high-voltage electric substations. To record energy sharing, communication with distribution system operators (DSOs) is fundamental. It is up to the Member States to establish if RECs can operate as energy distributors (in Italy, they cannot). The government must ensure that consumer, producer, and DSO rights are assured. It also describes how to activate alternative dispute resolution models, such as that of Ombudsmen. Integration of RECs in the energy landscape requires the adaptation of rules from large to small producers. Additionally, the discussion focuses on the challenges of securing funding and accessing technical expertise.
Legal principles include the following: the definition of a company (it must be a non-profit one), no admission of large energy companies (but not in CECs), autonomous and democratic governance, and voluntary participation. Activities that RECs/CECs can carry out include generation, consumption, storage, aggregation, and management of distribution networks. In [10], the authors hypothesize the use of multiple DC microgrids (MGs) for residential applications. The power demand is satisfied by the bus signal control strategy. In such an aggregation model, the regulation ensures the capacity of the MGs. With this model, the authors simulate a REC with five MGs with PV systems and battery storage, interfaced to a medium-to-low-voltage (ML-LV) substation. They modify the DBS (DC bus signaling) to (1) operate across multiple nanogrids simultaneously; (2) make the DBS adaptive, turning the control strategy on or off based on its contribution to the aggregator; (3) allow the aggregator to evaluate each nanogrid’s regulation capacity through the DC bus; (4) establish a hierarchy among the nanogrids to balance supply; and (5) verify the effectiveness of the control strategy through numerical simulations. In [11], the authors described a new aspect of how to manage technologies that ensure efficient energy supply systems, public satisfaction, and reliability through RESs. The solutions must (1) manage new types of RESs; (2) find new forms of power electronic interfaces to connect RESs to the grid; (3) flexibly manage highly variable RESs; (4) organize consumers, producers, and prosumers in the REC. This paper describes how to model different forms of RESs (photovoltaic, wind, etc.) and fit tariffs. A report of the analysis presents different RESs and how they are accepted by the public (welcome or not welcome) in a specific context, with their future use.
In an EU-based study [12], REC is a system to balance peak loads on the grid. The authors quantified the case of urban, suburban, and rural grids. A reduction in peaks from 23 to 55% can be obtained, at a cost of only 1% more than the present one. Systems to optimize the impact of RESs on the network are recognized and evaluated through a simulation model. In addition, the authors of [13] show the benefits and opportunities offered by the implementation of RECs among various EU states: obtaining 63% of the electricity from RES requires changing the logic and structure of the distribution network. The goal is to go away from the logic of maximum profit, which is currently pursued by the centralized systems. Consequently, the three principles of energy transition are as follows: power to consumers, intelligent networks and buildings, and management and protection of sensitive data. This transition highlights the need for individual states to transpose RED II into their national regulations. Thus socio-technical subjects underlying the implementation of RECs are (1) to encourage renewable clusters to minimize costs and maximize benefits of RES to be integrated; (2) to improve the social acceptance of RECs by verifying the relationships with their spatial distribution, size, and demography; (3) to anticipate the problems arising from already active operators; and (4) to encourage gender inclusion and weaker sections of the population. They propose two business and financing models, cooperatives (suited to Germany and Italy) and a consumer stock ownership plan (CSOP), for Eastern countries. In [13], they propose an optimization model based on an annual investment approach. They evaluate hybrid RES systems (PV and wind) with the LCOE (levelized cost of electricity). RECs with three members and four scenarios (only PV, only wind, or a mix of PV and wind) were analyzed. Their result shows a net gain of 87 k EUR/year. The integration of PV with wind in a hybrid system (HRES) presents undoubted advantages because it allows storage (re-pumping for hydro or H2 for PV and wind). The investment is more sensitive to PV.
The study [14] explores the proposal of three mechanisms to reward energy sharing in RECs: financial services, self-consumption services, and both. The authors simulate a REC with 100 households and 100 kW of peak production. The paper evaluates the impact of different sharing systems. With low demand, both Q1 and Q3 (equal sharing, as plant owners or non-owners) work well. Instead, with high demand (SM3), the regulatory mechanism rewards self-consumption. In the case of SM2 (both systems), the energy demand trend determines the premium. In [15], the authors’ emphasis is on external factors influencing RECs, such as fiscal measures in 39 countries. They present two scenarios: one with prosumers sharing the energy surplus and the other where consumers are joint owners of a PV field. The second case yields significantly higher savings, whereas the first is less convenient due to the low shared energy. Both are more affected by the tax regime. In [16], the authors describe the operation of a renewable energy community using a low-voltage grid, applying the concept of active dynamic limits for energy import and export. An energy community operator optimizes energy exchanges to enable efficient use of the low-voltage grid. In [17], the authors discuss why the EU decided to empower this new type of unit, the REC. Advantages include the possibility of investments in RESs and in larger plants, as well as an improvement in the acceptability of RESs. On the other hand, weaknesses include their operation on an intermediate scale and their smaller size than large energy companies, so investments in plants that exploit a large economy of scale (photovoltaic, for example) are less incentivized. The same happens for the large community, with a democratic consensus on decisions. The new RED III directive increases the energy production from RESs to 42.5% by 2030, with a target of 45%, relative to transport, industry, and buildings [18]. Authors in [19] present an integrated system for the distribution of renewable energy (wind, solar, and biomass) that uses H2 as storage, showing that a remarkable performance (46% economic reliability, 41–53% operational efficiency, and 95% distribution reliability) is obtained. The method is based on stochastic scenario-based optimization. In [20], researchers try to answer the question “What are RECs, what is their motivation, what contextual factors influence the birth and development of RECs?” in order to identify the possible developments of RECs within the next decade, as well as the social impact they could produce. Motivations are environmental protection, energy cost savings, energy autonomy, and local community development. Contextual factors include physical, technological, institutional, and community aspects. Social impacts include the local economy, the energy system, the acceptance of the energy transition, and the role of individuals in REC projects. The role these impacts can have in the acceptance of RESs is relevant, together with the role of regulation. Potential exists for future developments. Two dimensions, geographical (local or dispersed) and collective motivation (economic or relational), and three case studies, (1) Italian cooperative “ènostra”, (2) collectives’ self-consumption (CSC) in France, and (3) EU-funded project “WiseGRID” (pilot site in Ghent, Belgium), are analyzed. The situation in Austria, Germany, Denmark, and the United Kingdom is also reported. Ultimately, there are four types of RECs, depending on whether they are based on a geographical (local or dispersed) or motivational (economic or relational) contest.
Another paper [21] reports the definition and characteristics of CECs on the European regulation, presenting an innovative system to implement them. It consists of a connection between distribution systems through a switchable element. An optimization model has been developed to evaluate the obtained savings. The aim is to transpose the model into the national laws of individual Member States. Additionally, the challenge of connecting RESs to the grid through DSOs arises. The article explicitly deals with the connection across state borders. As a case study, the border between Germany and the Netherlands is considered. The use of switchable elements (which increase the flexibility of the grid) increases the capacity of transferring electricity between states without increasing the size of the grid. The benefits can be distributed among the members of the CEC. In [22], concepts, beneficial purposes, and key activities of RECs are described. European countries are at different stages of REC activation. A list of 13 reviews on the topic is reported. Three types of energy communities are recognizable: HEC (homogeneous), MEC (mixed) and SEC (self-sufficient), depending on the total net energy. Germany had more than half of the total number of RECs in Europe, in 2020, followed by the Netherlands and Denmark. However, there is still a large gap among countries. The barriers to activate more RECs are bureaucratic obstacles, unwillingness of potential members, economic and social obstacles, regulatory and legal challenges, and political, financial, and technical problems (grid barriers and losses, as well as voltage profiles). Consequently, recommendations for the future are suggested. In [23], a review study of academic research on RECs is reported. One hundred forty articles between 2018 and 2022 are examined. The results show how the development of RECs depends on overcoming regulatory, financial, and managerial barriers. It is necessary to introduce social perspectives based on energy sharing. The development of RECs can be supported by appropriate recommendations to politicians, stakeholders, and local communities. The most significant number of articles concerns Italy. Fifteen review articles in Europe are cited. In [24], a review of the EU evaluates how peer-to-peer energy sharing (AI-based) can support RES management. The significance lies in the evaluation of system configurations, energy sharing, supply mechanisms, and synergistic collaboration. The analysis shows how P2P sharing contributes to increasing the economic benefits for all members: it improves the efficiency of the electricity system, reduces storage capacity, increases RES use, and decreases energy loss in storage and transmission. The conclusions are as follows: 1—improves RES penetration; 2—improves system efficiency; 3—increases automation by decreasing human intervention; and 4—provides economic benefits to all members. Regarding the status and functioning of RECs in the EU, research studies from [6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24] provide a broad overview of the EU context. Some studies focus on individual European countries and are accordingly categorized, while other studies cover multiple countries, discussing cross-national scenarios related to RECs.
2.2. All EU Countries
Each EU country has implemented the EU directives on the REC constitution differently. This paper aims to survey the academic publications on RECs. A bibliometric approach to identify primary authors, affiliations, journals, collaboration networks, key topics, and countries (we followed) was used. The annual growth rate of publications on the subject is 43%. The evolution of scientific publications on RECs, the most active nations, authors with a higher impact, journals with more articles on RECs, the most active universities, and collaboration networks affecting RECs were considered. Italy, with Sapienza University and F. Ceglia as the author, are the most active, but the most cited articles are German, Portuguese, and Dutch [25].
2.2.1. Italy
The concept of RECs has seen significant implementation across Europe, with Italy serving as a notable example where innovative urban models, such as the condominium REC in the S. Salvario district of Turin, demonstrate the effectiveness of collective rooftop photovoltaic systems under evolving market regulations. The authors of [26] suggested models to evaluate the diffusion of photovoltaics on rooftops in the urban context. The results show how the rules of the electricity market influence the distribution and intensity of PV. The solution is the establishment of condominium RECs. The advantage of the one-to-many configuration compared to the one-to-one configuration is evaluated through modeling. The one-to-one configuration reaches 35% of potential members, while the one-to-many configuration reaches 65%. A theoretical study related to Turin in [27] presents the simulation of energy flows of a cluster of buildings that collectively behave as RECs. The results show how RECs integrated into buildings accelerate the diffusion of RES, with consequent cost savings. However, without administrative regulatory support, RECs are less attractive. The question is to what extent is it convenient to establish an energy community (EC) with respect to single self-consumers (SSCs). The results depend on various factors, such as the social status of residents, time spent at home, price variability, the occupancy rate of buildings, and vacation days. However, RECs are more resilient than individual self-consumers. Their convenience depends a lot on the prevailing market rules and the regulatory environment. The authors of [28] report the impact of scenarios with respect to the European community targets for condos. A condominium of 87 apartments, which uses PV, electric cars, heat pumps, and battery storage, is simulated. Retrofitting with PV always brings both environmental and economic advantages. The variability of the heat pump load can be reduced by storage. Ultimately, the diffusion of condominium energy communities in itself does not guarantee the achievement of the EC objectives but provides other incentives to the REC members. Condominiums are a key point for the energy transition. PV reduces its grid dependence by 50%, and with storage, it reaches 90%. The research work in Italy [29] handles two different items: the first develops a mathematical model of the energy flows exchanged between the members of a REC, while the second proposes the Shapley model (to evaluate costs and benefits of infrastructures) to fairly distribute the advantages deriving from the application and operation of RECs. As a result, the authors establish that within the Italian regulatory system, it is economically advantageous to organize RECs for investors. In March 2020, following the acceptance of the European directive on self-consumption and the RECs (articles 20 and 21 of RED II, 2018/2001), it was established that certain components of the electricity tariffs are not due to the shared quota, and incentives lasting 20 years are released. Two visions are reported: one is a holistic vision model of the RECs as a multi-source energy system, and the other is the practical implementation of a REC in real life to obtain a valid, stable, and reusable model. As a consequence, the authors propose a two-step sequence: the first is the definition of the optimal investment for the communities, and the second is the ethically corrected distribution of the REC revenues. The model is applied to a case study in Chiou (Aosta Valley). In [30], the authors deal with the advantages and disadvantages of RECs, whose relative impacts (time, scale, type, group, and stakeholders) are classified and provided with indicators. The results are applied to two case studies: two RECs in Italy, both cooperatives but with two different business models, with one in the Alps (E-Werk Prad, in South Tyrol, Italy) and the second, “Energia Positiva”, in Turin, with PV and wind plants. Both give a positive contribution, both in environmental and economic terms. The list of REC impacts and relative indicators is discussed, such as timing, scales, types, groups, beneficiaries, and stakeholders. Examples of two RECs are reported, both structured as cooperatives, but with different business models. Two goals are foreseen: creating a taxonomy to explain the multiple impacts of RECs and providing confirmation of the impacts (both positive and negative). In [31], the authors critically examine the concept of energy communities within the context of the low-carbon energy transition. They identify that the term “energy communities” is used broadly, often oversimplifying diverse realities. The authors propose a taxonomy to distinguish communities by two dimensions: (1) “place-based” vs. “non-place-based” depending on their spatial connection and (2) “single-purpose” vs. “multi-purpose” depending on whether the community’s focus is exclusively on energy or includes broader objectives. The article uses examples to illustrate this taxonomy. It discusses the policy implications emerging from these distinctions, highlighting the need for nuanced regulatory frameworks tailored to different types of energy communities. The photovoltaic, hydroelectric, wood biomass, and biogas systems are discussed and modeled.
In [32], the authors establish that in Italy, besides pure engineering and economic knowledge, REC development also requires human and social sciences expertise. Therefore, the role of sociology is emphasized concerning the history of sociological influences on the energy transition; the current sociological debate on the energy transition; the importance of social and territorial inequalities (e.g., conflicts on the location of plants, energy poverty, and access to energy), i.e., how to access the RES; energy saving and energy efficiency; and what favors or disfavors weaker social groups. Thus, the involvement of society in the energy transition is outlined. In [33] the author’s work presents the development of a flexible mathematical model for energy management within smart grids (SGs), focusing on energy communities and their role in electricity grid balancing and PV production. It implements energy-sharing strategies such as peer-to-peer and vehicle-to-cluster interactions, optimizing the use of distributed energy resources, including prosumers, consumers, storage systems, and electric vehicles. The model predicts electricity demand one day ahead, enabling better organization of renewable energy and storage to minimize grid fluctuations and enhance self-consumption and self-sufficiency. Simulation results demonstrate the improved renewable energy integration and grid frequency regulation, highlighting the model’s effectiveness for SG energy management.
The authors of [34] in Italy, Turin, use demand-side management (DSM) to simulate the social and psychological behavior of residential users of RECs and evaluate the economic convenience based on such behavior. Simulation involves electric load shifts and differentiation of RESs. The result highlights the importance of customer satisfaction and a user-oriented approach. Three subjects are responsible for the simulation: the aggregator, which manages storage and RESs; the prosumer; and the market. The opinions of users highly influence the results. In [35], the researchers present the analysis of a new scenario for local energy planning, mainly considering PV and electric vehicles. It is applied to the island of Pantelleria to evaluate the effect of the transition from diesel to PV. The optimal scenario provides a CO2 reduction from 45% to 52% and a cost reduction from 6% to 15%. Priority is given to the use of RESs. The aim is to plan local actions to decarbonize islands. The highest reduction (70%) is obtained with PV utilization. User involvement results are essential. In [36], the authors report the results of the ComER project (methods and tools to manage RECs) to face the practical problems of REC implementation. Usual problems of the transition from a centralized to a distributed generation are faced. Project phases are modeling of distributed resources, REC management methods, forecasting algorithms, measurement and control tools, implementation of a commercial platform, and validation. Three REC configurations were studied, and the best among them was defined based on the simulation results. In [37], a model that analyzes and sizes plants for REC use is presented. The case of Tirano, a municipality in Valtellina with 9000 inhabitants, with district heating is reported. A Rankine cycle system with biomass combustion for cogeneration, a mini hydroelectric plant, and a distributed PV is proposed. Considering that the Italian government had adopted RED II, the best configuration was obtained with 1000 kW of PV and 2.1 MW of biomass, based on the Ranking cycle. Such a solution’s payback period is 5 years. In [38], researchers present a model describing a new optimization methodology with combined heat and power (CHP) production from RES for two communities connected by a MG. Solar and photovoltaic, with integration of liquefied petroleum gas (LPG) boilers for heat generation, were used. So it is possible to cover 79% of the electrical load and to reduce the CO2 emissions by 4129 tons/year. The study in [39] deals with the dilemma to join or not to join a REC: the answer can be regarded under two points of view: (1) outlying different implementation solutions of the RECs in different European countries (Germany, France, Greece, Portugal, and Italy) and (2) using mixed-integer linear programming (MILP) to encourage the participation of prosumers in the REC. Applying the results to Magliano Alpi [40], the oldest REC in Italy (2020), shows that the parameters to encourage citizens to participate in the REC were correctly identified. Four performance indices are identified, including 35% of the required energy satisfied by the renewable plants and 19% of it by self-consumption. The produced power was 25% higher than the consumed. With a more effective time distribution of consumed energy, 54% of the electric required load can be covered. Another result turned out to be that new investments in RES plants are less profitable if the REC is already producing 50% of its needs.
The authors of [41] defined that the process of establishing and developing RECs is made up of three phases: project, creation, and operations. Project: This phase includes establishing the size of RECs, the type of RES, and storage, and defining the economic model. Creation: This phase includes finding the means, procedures, and resources needed to implement the RECs; defining the legal model, the role of stakeholders, and governance of the REC; finding funds; and obtaining permits. Operations: This phase includes activities to monitor, organize, and optimize resources, such as verifying the day-to-day management of the REC, maintenance of the plants, monitoring of energy flows, and sharing of revenues. These are both technical and legal/organizational/economic steps. The digital platform (private or from a European project) can address some of the problems encountered due to the lack of competence among general citizens on related items. Three types of platforms are described: commercial, European projects, and open-source. Each step can be associated with a KPI (key performance indicator). Result: The project stages and operations are covered by many platforms, while their creation is only covered by those of European projects. In the study by [42], the authors propose a methodology to identify urban areas in which the establishment of RECs can be encouraged. The presented case study is based on the municipality of Pagani Salerno, Campania Region, Italy. Priority is given to urban centers and rural areas, both of which are optimal for establishing RECs. The main objective is to fight energy poverty. A selective criterion is the presence of already built plants. In the region of Rome, Tor Sapienza [43], conditions are evidenced for founding a REC in a location where the renovation of a social center had been carried out. The analysis of the renovation interventions also concerns the sustainability of materials, as well as energy. Heat pumps and PV are planned, and zero emissions are obtained.
In the study conducted in Savona (Liguria), the research paper [44] deals with the integration of battery energy storage (BESS) in the REC. The authors evaluate the effect of cooperation. High importance is given to the dissemination of relevant information on energy production and consumption. Tariffs and incentive systems are taken into account, together with the key role of the University of Genoa and the public administration. A method to overcome the complexity of operations related to REC constitution is described in [45], which deals with prototyping, implementation, and management. For this reason, best practices for administrative, technical, and technological management are essential within the Italian regulatory environment. The paper considers the positive energy districts (which produce more than they consume). The Italian regulatory authority interprets the European directive in a virtual way: widespread self-consumption. The paper describes the regional and national support mechanisms for the establishment and operation of RECs and compares them with other European countries. In Italy, there is a leading role of public administrations, which can guarantee the social aspect of the initiatives, but they can slow down the process due to bureaucratic impediments [46]. Public administrations have played a central role in promoting social equity, but procedural inefficiencies risk delaying the implementation. The authors discuss the regional and national support mechanisms for the establishment and operation of RECs and compare them with other European countries.
In [47], a technical–economic analysis specific to Florence is described, specifically on batteries, comparing three different management systems. The authors modify the standard management model (not designed for RECs) to take into account multiple users and use an optimal system (not real but hypothesized) to evaluate its benefits. A REC model with five consumers and three prosumers is developed, which uses the NPV (net present value) to evaluate the performance. As a result, when economic and environmental convenience do not coincide, incentives are needed to correct this. In [48], the authors assess that Italy is one of the first countries to implement the European legislation. However, the number of RECs remains limited, mainly due to bureaucratic obstacles, a lack of guidelines, and uncertainty on operational aspects, e.g., the method of dividing the obtained incentives. For this reason, the legislation needs to be better updated. At the time of the article, there were 17 RECs with a power of 300 kW, while in Germany, for example, there were 1750. Collaboration between public administrations, ESCOs, and the private sector is essential. In [49], the way to design, make operative, and monitor RECs is described. The presented case study concerns 17 apartments in Catania (Sicily) equipped with PV and storage. A 38% reduction in CO2 emissions is achieved, alongside support for 51–67 families through revenue generation, and a significant real and virtual impact on the electricity market is seen. Objectives, activities, milestones, and a timeline of activities define the roadmap. Two scenarios were predicted: one basic and one with a PV increase. In [50], the design of cybernetic physical systems that take into account consumption, for which energy-conscious architectural models integrating SGs are developed, from the outline to the content, was described. This optimized functioning of RECs is based on three contributions for the management of the RECs without storage: AI, Stack4Things, and complex event processing, all based on the Internet of Things (IoT). It works if the members of the REC cooperate and follow the received instructions. In [51], in Italy, the authors carried out an evaluation of the relationship between organized civil society in RECs and the energy transition due to the consequent significant change in the energy system. Social attitudes and cooperation between citizens are investigated at the level of different European countries. In the Mediterranean, the tradition of RECs is well established, while it is lacking in Eastern countries. The role of organized civil societies, as non-profit NGOs and third-sector institutions, is fundamental. The survey was conducted through interviews with 18 interviewees. In [52], it is reported how the maximization of self-consumption can be obtained by simultaneously combining energy generation and demand. Thus, consumer habits must change so that production and consumption can match as much as possible. In this context, MILP can increase the sharing percentage. As a case study, an Italian multi-family community is taken. Changing consumer habits can lead to more sharing between energy supply and consumption. In [53], a method for the management of a REC is proposed, which compares different configurations. The method is tested by simulating three case studies in different latitudes (Turin, Rome, and Palermo), which are residential places with PV on the roof, heat pumps, and electric and thermal storage. The system, called “RECoupled”, is the upgraded version of a previous system to make it multimodal, with many energy sources, and includes different components (e.g., heat pumps) and storage methods. Unfortunately, the economic, environmental, and energy points of view are often contradictory. The simulation allows for the identification of alternatives at the country level.
In [54], to predict the REC welfare increase and energy poverty decrease due to the constitution of local RECs, an index is proposed to account for the multidimensionality of energy poverty. The method is applied to the municipality of Pirani, located in the Province of Cagliari, Sardinia Region, Italy. In [55], the authors deal with the advantages of positive energy districts (PEDs) supporting RECs to fight climate change and energy poverty. Disparity among European countries has been outlined: 198 RECs in Italy, 1 in Bulgaria, and 4848 in Germany. The Italian situation is greatly influenced by the national legislation.
The research work in [56] deals with the progress of RECs in Italy, taking Assisi as an example, and outlines the pivotal role of the public administration. The analysis takes into account technical, economic, and energetic items. Assisi’s income significantly varies with the cost of energy, the remuneration for the sold energy, and the value of the incentives due to energy sharing. Through SECAP (sustainable energy and climate action), Assisi can reduce CO2 emissions by 40% by 2030. The plan includes nine actions. The role of public administration involvement is fundamental. In [57], the authors verify the socioeconomic and legal conditions for the establishment of RECs based on current legislation and identify risks and advantages of creating new professional profiles to address the challenges of this market. The limited number of RECs currently in place hinders the definition of general guidelines, and the local market, although interested, does not yet fully appreciate the benefits of such initiatives. Through interviews and a bibliographic review, it was clear that there is still a need for consensus to increase, even if an exhaustive literature review about this subject exists. In Italy, there is still a lack of clarity in public administrations. The research in [58] reports the results of implementing a network of small villages in the Madonie villages (Sardinia) to ensure their subsistence. Guidelines are established, which can also be applied to other similar realities.
Moreover, in [59], the conclusions of the Horizon Europe KNOWING project are related to Naples, S. Giovanni al Teduccio. Effects of RECs on urban architectural design are considered, together with the role played by the urban context in which REC elements are inserted (panels, canopies, pylons, charging panels, etc.). In [60], a possible solution is presented with PV panels housed on the roof of schools and by exchanging energy with adjacent residents. Different possible scenarios for the evaluated conditions are the NPV (net present value) at 20 years = 51 ÷ EUR 478 k; the IRR (Internal Rate of Return) = 9.5 ÷ 88%; and the PBP (payback period) = 13.6 ÷ 1.1 years. All these values depend on the geographic location, system capacity, installation costs, and energy prices. The Italian situation is mainly given by small plants (~100 kW) and RECs with fewer than 100 members. In [61], a review of platforms for designing RECs in Italy is presented, according to RED II, based on four data types: input, output, optimization, and openings. In the considered software, input and output are generally present, while optimization and openings are rarely present. The authors suggest that it is necessary to make data openly accessible and methods easier and to establish shared methods to compare the results. The following programs were considered: GSE, ROSE, RECON from the National Research Agency (ENEA), and HEXERGY. Similarly, in [62], SMEs’ vision about RECs in Lombardy is discussed: even if they appear interested, they lack knowledge and experience. From this, the fundamental role of public administrations (PAs) becomes clear. In Lombardy, despite the incentives and efforts of PAs, RECs have not yet taken off. It is therefore a question of increasing the level of knowledge on RECs from the SMEs’ side. In [63], regarding Italy, the use of hydrogen as an alternative to batteries for energy storage is explored. The paper deals with modeling and optimizing the energy systems, with hydrogen used for design, sizing, and management. Unfortunately, the lack of reliable data produces high variability in the model results. For this reason, a data archive about the production, compression, storage, and use of hydrogen is needed for electrolyzers, fuel cells, storage batteries, compressors, and vessels. In [64], the advantages (economic, environmental, and social) and disadvantages (regulation changes, access to finance, and public awareness) of RECs are addressed. The latter overcome the former if the scientific community provides information to the political authority, industrial stakeholders, and local communities about the activation of RECs. There is growing attention to PV electricity production, despite being low on thermal energy. The authors of [65] discuss how greenhouse gas emissions are reduced by mixing methane and 10% hydrogen. They point out the link between the insertion of hydrogen into methane and the greenhouse effect. In [66], guidelines were indicated for organizing RECs in ports, which are notoriously very high energy consumers. A numerical model was developed to evaluate the energetic and economic convenience of RECs in ports, using solar irradiation, wave motion, and battery storage. The paper examines the convenience of virtual aggregations of users. So 60% of consumption can be covered by RESs, and 90% of self-consumption can be obtained. The payback period is 6 years, which drops to 2–4 for small installations. Savings in 20 years can reach EUR 5 M. As a case study, the port of Naples is checked with more RECs (seven).
Authors in [67] propose a business model for planning and designing the phases of RECs. A sensitivity analysis defines the optimum number of members, PV size, and the overall economic impacts. The case study in Italy demonstrates the relationship between the number of members and the PV size. The authors of [68] delineate the fundamental features that define the REC conceptual model. A general framework is presented to increase the effective use of RESs. They give a general path for the massive renovation of buildings located in densely populated areas. The circular economic model and the REC conceptual model were developed for four case studies (Naples East, Brindisi, Magliano Alpi, and Biccari). In [69], the authors identify the areas where it is more suitable to install RECs in Italy, with particular reference to high enthalpy geothermal energy, both for thermal and electrical production. The problem is to know the real availability of RECs. The importance of the thermal load is outlined, as it represents 49% of the total energy consumption in Europe and contributes to reducing energy poverty. The geothermal potential in Italy could supply the entire energy load. A simulation is carried out for Pisciarelli (Pozzuoli).
In [70], the authors evaluate different decarburization procedures through the analysis of the energy balance, CO2 emissions, costs, and the effect of incentives. They also take into account future scenarios with hotter and hotter summers; thus these scenarios foresee an increase in air conditioning use. The most suitable solution is heat pumps coupled with solar panels. The importance of different calculation methods is outlined. In Europe, buildings are responsible for 36% of CO2 emissions and 40% of energy consumption; hence the importance of renovating existing old buildings is underlined. The problem of bottom-up or top-down building load simulation models is faced: UMI and EnergyPLAN were tested one after the other. Hydrogen and storage are not convenient. The best solution results from PV powering heat pumps.
In Bari, the study [71] describes the energy and economic convenience of RESs for individual buildings and aggregates. As a case study, a community with residential buildings, a university, and tertiary services is chosen. The electrical surplus is shared, but the university has a large overproduction. In conclusion, it is better to have members of the same type in a REC. In [72], the authors state that RECs can integrate different actions: generation, storage, supply, deferrable, and controllable consumption. As a case study, the REC of Savona (Liguria) in collaboration with the University of Genoa is described, and the potential of battery storage is evaluated. A scenario is presented in which users do not cooperate. Battery storage of a significant size can constitute a system to make the grid more flexible and to increase convenience for citizens. The importance of information and sharing is outlined. The main problem is to have the availability of an efficient grid management system.
The authors of [73] describe the ENEA RECON program for the assessment/simulation of RECs. Italian regulations and procedures are also summarized. A case study is a REC in Northern Italy with a municipality, a school, and the Naval League, with or without 200 consumers. Pure residential consumers are fundamental to defining the REC’s economic convenience. Moreover, in [74], the ENEA SIMUL-REC program was used to evaluate the advantages and disadvantages of different REC configurations. The case study is Lignano Sabbiadoro (Venice province) with 88 REC members and 50 electric load profiles (with real data, not simulated). It shows that the economic convenience of a REC depends on three factors: self-consumed energy, shared energy, and energy supplied to the grid. The role of the BESS is fundamental for self-sufficiency. In [75], the authors evaluate the convenience of two different approaches: demand-side engagement and optimized demand-side engagement (incomes redistributed according to a genetic algorithm). Load delay strategies were considered and evaluated through three different economic efficiency keys: optimization of incentives gained from energy sharing, social cohesion through collaborative involvement, and environmental sustainability from the optimal use of the generated energy. Relevant investments in infrastructure are required. The case study is the town of Riccomassimo-Storo, Trento province. It results in the optimized method providing the REC with higher gains.
In Italy, the authors of [76] explored how the optimization of PV for industrial partners is obtained on the basis of their ATECO code profile. They show that it is possible to increase the NPV (net present value) from 25 to 75%. The importance of a careful selection of REC members is underlined, because it is better if they are complementary rather than similar. Meanwhile, in the study by [77], the Italian political and regulatory environment is examined to identify the key factors influencing the REC operations: governance structures, economic incentives, and social inclusiveness. Also, the regional inequalities, legal ambiguities, and potential conflicts with other energy policies are highlighted. A key role is attributed to PV, together with all other RESs. In the paper, an attempt is made to verify to what extent Italian legislation transposes European laws. Key points to be addressed include simplification of bureaucratic procedures; an increase in support mechanisms; enforcing the coordination between regions to reduce disparities; and assuring long-term political stability. They are considered fundamental to supply adequate information to potential members.
In another study [78] conducted in Padua, psychosocial factors (ability to influence social and political systems) that can influence the social acceptance of RECs are considered. From the analysis of 107 questionnaires, it appears that RECs are generically accepted, but the presence of a false altruism is also outlined. The need to increase individual participation in social initiatives is put into evidence, e.g., through a shared management of RECs.
Moreover, in [79], the authors state that in RECs, collective self-consumption (sharing) must be maximized. If there is no efficient system for measuring consumption and the electrical load, this could be a problem. The article proposes an AI-based method to extrapolate hourly loads from monthly consumption; this method involves three phases: identifying the typical consumption, entering it into the random forest model, and developing the trend of hourly loads. The model provides an error between 20 and 26% of the forecasts compared to the real load, as well as an error of 8% and 0.12% on a monthly and annual basis. Ref. [80] describes how a rooftop PV can change the sector of new or existing buildings. The article offers a guide for the best orientation of the panels and determines which roof slopes are most suitable. A Monte Carlo simulation of a REC with 60 members and 30 PV plants on the roof (tot 150 kWp installed) is carried out. East and West orientations are comparable, even better than South ones, due to the sharing of energy produced in the morning and evening. In [81], it is demonstrated that the uncertainty in PV production, together with that of consumption, can influence the balance sheets and performance of PV-based RECs. The authors realize a model with 10,000 production profiles, with a 50 kWp plant serving 100 residential consumers. The relative uncertainty is around 2–3%. There is an overestimation of the energy produced during the months with the highest production, which demonstrates the need for a statistical evaluation. The paper by [82] describes the tools developed by ENEA (National Agency for New Technologies, Energy and Sustainable Development) to support RECs. Three REC features are handled: digital tools, business cases, and the observatory. This last one is made of the following: 1—pre-feasibility analysis through a geoportal for RECs; 2—the RECON simulator; 3—SIM and DOMUS, which are websites for citizens; 4—the SIMUL and CRUISE tools for supporting citizen in energy systems; 5—a local economy tool; 6—an energy community listener; and 7—a public energy living lab.
2.2.2. Germany
Germany’s strong legal support and feed-in tariff schemes have made it a frontrunner in REC deployment, where energy cooperatives and citizen-owned initiatives thrive within a decentralized energy market. The forecast of electricity production and consumption of RES is necessary to RECs, but it can be affected by significant errors. So in [83], the uncertainty due to these forecasts is evaluated, and some forecasts are a posteriori validated. In this way, the support that RECs give to the grid is evaluated by attenuating the peak loads. A reduction in demand peaks of 21% is achieved, along with a 49% increase in power supply, a 12–16% rise in the self-consumption ratio, and a 7–10% increase in self-sufficiency. In [84], a German-based study claims that RECs are a good opportunity to reduce the suffering of the electric grid due to overloads. Based on Austrian and Italian regulations, a case study in Germany is addressed, demonstrating the effectiveness of peak reduction up to 50% on the grid’s performance. The study by [85] is focused on family convenience to join RECs from both the environmental and economic points of view. It also evaluates the influence of policies to combat energy prices, including natural gas, and of tax reduction for investments in RESs. This influence results in a significant influence. The study by [86] observes that PV and BESS in German multi-family buildings are less developed than single-family. The landlord-to-tenant (L2T) project tries to overcame this gap. The electricity price changes the financial viability of L2T, and passing from 4 to 22 members reduces costs from 4% to 17%. Feasibility depends on many factors: electricity prices, regulatory framework in Germany, and building peculiar characteristics. Moreover, the authors of [20] explore the situation of RECs in Germany, Austria, Denmark, and the United Kingdom. In [21], the specification on the European regulation of CEC is reported, with the connection across state borders: case studies between Germany and the Netherlands are also discussed. According to the study by [22], Germany had more than half of the total number of European RECs in 2020, followed by the Netherlands and Denmark. The cooperative model, which is powerful in Germany and Italy, reflects a broader European push toward democratizing energy systems through CERs, which aim to empower consumers, promote intelligent grid integration, and protect sensitive data [33]. Comparative insights from other EU countries, including Germany [39], outlie different implementation solutions of the RECs in different European countries (Germany, France, Greece, Portugal, and Italy). Regarding Germany, the inclusion of RED II into its national law has been notably complex and fragmented, although Germany is highly suited to implement RECs [87].
2.2.3. Portugal
In the broad comparative analysis of REC across five European countries—Germany, France, Greece, Portugal, and Italy—Portugal’s implementation reveals distinctive features in regulatory support and community engagement strategies. As in [88], they examine 34 cases to (1) study the interaction between the actors involved to define the elements of collaboration; (2) activate the corresponding technologies; and (3) verify how the composition and functions of ecosystems are specific to virtual systems. As technological facilitators, the authors identify IoT devices, smart meters, smart software, peer-to-peer networks, distributed accounting, and blockchain, all systems characterized by the exchange of information and energy. In Lisbon, in the study by [89], a model is developed to assess which parameters maximize efficiency and convenience of RECs: different types of consumers and relative differences in energy demand, technological scenarios (PV, batteries, and electric vehicles), and distribution (collective self-consumption and peer-to-peer delivery) were considered. Cost savings up to 42%, 48–53% for residential consumers, 43% for hotels, 44% for commerce, 13% for industry, and 5% for universities are obtained. Sharing/selling the PV surplus represents both an economic and environmental advantage for both prosumers and consumers. When the local RECs’ classification and sizing in Portugal are considered, the need to involve energy consumers is outlined in [90], where a platform to gather producers and consumers in a REC is proposed. In this platform, three ways of constituting the REC are defined: homogeneous, mixed energy, and energy self-sufficiency, which lead to the definition of three algorithms. The platform is applied to a REC of 233 members in nine cities in the north of Portugal (Porto District). The best algorithm was the linkage one, as also demonstrated by the performance indices. It is also important to take into account the size of the REC.
In organizing RECs, there are still many problems in management, governance, and the definition of incentive distribution. The paper by [91] defines the collaborative REC and, through simulations, the author identifies its potential advantage. In [92], optimization of the energy transitions is reported using a linear programming model with storage integration, based on maximizing the REC gains: a difference when loads can be taken from the grid or when storage can be used is obtained. Two scenarios are considered: the first without and the second with storage. In the first case, in winter, the amount of energy withdrawn from the grid is high (50%), while with storage, it is much lower (16%). The study by [93] presents an analysis of the energy sharing coefficients proposed by the Portuguese authority. It turns out that coefficients that vary over time are more convenient for large consumers, but for small ones, fixed coefficients result in preference. In [94], multiple-objective particle swarm optimization (MOPSO) is used to evaluate the best strategy/solution in the “particle swarm”. Four case studies (scenarios) with four different energy strategies are modeled. The optimal solution for size and storage is found. Energy management systems (EMSs) can optimize the energy flows and manage the different sources. Scenario 4 (sharing of distributed energy and energy storage before charging the batteries) is the most promising. In [95], a home energy management system (HEMS) and a two-stage collaborative energy management strategy (TCEMS) are proposed, both of which include technical and economic aspects. In practice, it is a matter of equally dividing the energy produced (first stage) and managing the energy surplus and deficit. The paper by [96] deals with the management and optimization of distributed energy resources (DER) individually and in communities. This is achieved through a REC management program in which variable loads of consumers are spread according to electricity production, prices, and personal experiences to match grid availability. The simulation carried out on a REC with 50 apartments shows a saving of 6.5% with a peak of 12.5% in summer and an increase in self-consumption of 32.6%. The Flexigy project aims to develop an integrated platform to manage energy flexibility. The REC management strategy works at three levels: single member/home, REC, and network. The created algorithm allows for maximizing the flexibility of the energy supply by providing load activation. In [97], this research focuses on forecasting 24 h electricity consumption for residential households within a local energy cooperative in Portugal. It employs various machine learning (ML) and statistical models like autoregressive integrated moving average (ARIMA). The ARIMA algorithm was the best for cluster 1, while the long short-term memory excelled in cluster 2. This work is a forecasting model study, integrating M and techniques for energy consumption prediction within RECs.
In the Portuguese context, the study by [39], as previously discussed in detail (Section 2.2.1), highlights the country’s progressive approach to REC regulation, outlining different implementation solutions of the RECs concerning other European countries (Germany, France, Greece, and Italy).
2.2.4. The Netherlands
The Netherlands has emerged as a key player in shaping RECs through socially rooted initiatives and knowledge-sharing models, as highlighted in [98], which explored the factors for the success of RECs. These factors are related to the initiatives themselves, to the relationship between initiatives and communities, and to government support. The examination of 14 Dutch cases shows that internal organizational factors are linked to collective and individual items; i.e., all factors contribute to the success of RECs. In a district heating system (DHS), in [99], the AI-based HELIOS program is presented and tested in comparison with 10 data-driven model cases, and it is the most efficient one.
Moreover, the authors of [21] emphasize that a CEC in the Netherlands presents an innovative case study between Germany and the Netherlands.
Political impacts of RECs (as decentralization and democratization of energy), as described in RED II, are discussed in [100]. Also, a proposal to recognize RECs as legal entities in order to promote the energy transition is presented, particularly for the UK and the Netherlands. In this way, it is possible to suggest to the EU Member States how to implement RED II. The authors propose an institutional socio-legal approach to constitute a civil network through RECs.
2.2.5. Latvia
Bridging policy and local motivation in RECs, in Latvia, shows the potential to support an efficient energy transition. However, its progress depends on aligning EU policy goals with local stakeholder motivations such as cost savings and energy independence. In [101], a study about Latvia, Norway, Portugal, and Spain is carried out. Studies on how energy justice is perceived and implemented through RECs were carried out with interviews in the four countries, based on RED II. The analysis shows that RED II can contribute to economic, social, and environmental sustainability.
2.2.6. Poland
In [102], a study about Polish energy cooperatives and how they contribute to the increase in renewable source exploitation is handled. In Poland, a transition from net metering to net billing occurred. Consumers (with their generation systems), producers (with PV covered by net billing), and prosumers (together with cooperatives) are all affected by significant cost reductions. In Poland, in addition to energy cooperatives, collective prosumers, energy clusters, and CECs are present, all to increase energy self-sufficiency. All these organizations contribute to fighting energy poverty. In Poland, the need for winter, spring, and autumn heating is relevant. So [103] compares two options: the centralized use of renewables (biogas, sewage, and geothermal) against local heating with thermal panels, PV, and heat pumps using geothermal energy (GSHP). In Poland, 20 district heating systems are present. Most of the fuel used is coal, with RESs only at 12.3% (among them, biogas is the most developed). The centralized scenario seems to be the best solution to reduce costs, as the infrastructure is already present.
2.2.7. Switzerland
In Switzerland, Zurich, the authors simulated 5000 urban buildings to evaluate how to incentivize PV adoption. Three policy scenarios are presented: no solar community, a community with adjacent buildings, and a community with buildings within 100 m. The most permissive system (within 100 m) allows for the installation of 20% more PV by 2035 [104].
2.2.8. Norway
In terms of SME engagement and policy alignment in RECs in Norway, RECs are shaped according to both local business preferences and broader EU policy frameworks. SMEs show interest in RECs when offered local, cost-effective renewable energy with minimal management effort [105]. Preferred models include leasing infrastructure and forming long-term agreements with local suppliers. Meanwhile, ref. [101] highlights that aligning REC initiatives with stakeholder motivations such as energy independence and sustainability is crucial for ensuring just and inclusive energy transitions in Norway.
2.2.9. Czech Republic
Since there is no systematic approach to the REC project, according to the paper by [106], this work is related to the EU’s aspiration to become a leader in environmental energy sustainability. Four regional case studies are presented: the Měňany village with 308 inhabitants with a biomass district heating plant, Kněžice with a municipally operated CHP plant, Hostětín (240 inhabitants) with biomass and solar systems, and Dolní Lhota with a PV plant to be used together with a wastewater treatment plant. It concludes that RECs produce many positive impacts, including the fundamental three: economic, environmental, and social. However, technology, politics, and mentality must change. The involvement of the public administration is essential.
2.2.10. Spain
If the grouping of members in RECs by consumption and resource types represents an advantage, this advantage significantly decreases if the grouping is improperly organized. The paper presents a way to maximize PV profits with a genetic algorithm optimizing the sharing of produced and consumed energy. The algorithm improves performance and reduces CO2 emissions. The simulated case study presents residential prosumers of 128 families. In conclusion, the lack of an optimized design and operation guide increases electricity production, decreasing self-consumption, but lowers earnings [107].
In [108], the “technique of the order of preference by similarity to the ideal solution” (TOPSIS) is used, and 17 RECs are analyzed in Spain, ranking them on the basis of 10 selected indicators. Increasing the energy self-sufficiency of RECs leads to achieving independence of energy demand, decreases government intervention, and contributes to reducing problems related to energy inadequacy. In practice, a warrant of sustainability is obtained. Among the 17 RECs, ref. [108] identifies the sustainable, relatively sustainable, moderately sustainable, and less sustainable ones. Moreover, ref. [109] evaluates the economic impact of Spain’s updated electricity tariff framework and the potential shift from static to variable energy-sharing coefficients within local energy communities (LECs). Using a linear programming model applied to a case study in Valencia, the authors demonstrate that dynamic energy allocation increases self-consumption and reduces energy costs, particularly when coordinated with time-sensitive tariffs. It used policy and economic modeling focusing on energy-sharing mechanisms and tariff structures in LECs. Authors in [110] proposes an integrated system of efficient energy management and production from wind and hydroelectric sources. An off-grid system is simulated. The aim is to maximize electricity demand coverage, using wind as a base (variable) and hydro as a backup to ensure supply. In [111], 16 business models to verify the sustainability-related benefits of RECs and their contributions to sustainable development are presented. This contribution can be divided into supply-driven, demand-driven, and community-driven. It turns out that the greater the decentralization of ownership and distribution, the greater the number of factors that contribute to the success of RECs. The study by [112] introduces a comprehensive data-driven framework for designing RECs, integrating machine learning (ML) with life cycle assessments (LCAs) and life cycle costing (LCC). The framework enables the identification of the optimal configurations of renewable technologies (e.g., PV, wind, and storage) by predicting energy performance, environmental impacts, and cost efficiency. By combining ML predictions with sustainability metrics, the approach supports decision-making in community-scale renewable energy planning. The tool helps to maximize environmental and economic benefits while minimizing emissions and investment risks and is adaptable to different climatic and demand scenarios.
2.2.11. Belgium
Belgium is recognized as one of the first adopters of RECs, supported by favorable national policies and local government involvement that facilitate citizen participation and decentralized energy ownership [20]. The authors of [113] present parameters on which the convenience of REC depends on, which are electricity tariffs, the rate of electrification of heat and transport, the price of RES and storage, and the price of internal electricity exchange. An integer/linear model is developed for RECs in Flanders, Belgium, which includes 156 scenarios. Results: A REC has the potential to reduce costs by 10 to 26%, depending on the level of electricity tariffs and the adoption of flexible systems (heat pumps and electric vehicles), and makes the adoption of storage attractive. However, compared to individual CSOs, the increase in convenience of RECs is only 4–6%. The economic efficiency of RESs depends on many interdependent factors. The study by [113] evaluates the effects of electricity tariffs, the electrification ratio of heating and transportation, the prices of renewable sources and storage, and the prices of internal electricity exchange. This paper employs a linear mixed-integer model in a case study of Flanders. The results show that RECs can reduce energy costs by 10–26% and CO2 emissions by 5–13%. An unsolved problem is to identify the motivation of potential members to join RECs and how to overcome it, e.g., lowering entry barriers, increasing environmental sensitivity, and focusing on financial reward. One hundred fifty-six plausible scenarios are presented, and the following factors are considered: CAPEX (capital expenditure), tariffs, and investments. Capacity- and volume-based tariffs are more important, and the former are predominant.
A performance model of RECs is presented in [114] for the case where individual members consume and invest. The impact of RECs on the grid is evaluated through the calculation of operational indices, such as the peak/average ratio, line loss, etc., and an investment model is developed. The members are the household consumers owning PV systems, electric vehicles, batteries, and heat pumps. A case study is presented with 55 members. It is found that the REC favors PV investment and controls the impact on the electricity grid. As a benefit, minimization of self-consumption is ascribed. The control (decision-making process) on the method of distribution among members of profits generated by the surplus energy produced by a REC is optimized, so costs are minimized. Two optimization methods are proposed, based on the application to the REC structures and future consumption forecasting, and the third one only optimizes the asset. The method is applied to two RECs with four consumers, one producer, and a battery. Due to the relevance of the structure, the best solution is the third one [115].
2.2.12. France
In France, the study in [116] presents 16 self-consumption configurations of RECs, which contain different types of industries, and compares them with a mathematical model that considers economic, environmental, technical, and social effects. The most effective configuration combines both individual and collective self-consumption. However, collective production produces 65% more earnings, a 33% decrease in CO2 emissions, a 21.4% improvement in self-sustainability, and 175% more jobs. Storage increases the degree of self-sufficiency. In RECs, energy flow modeling is used to identify the most effective configuration, in terms of RES generation, storage capacity, or satisfaction of energy demand profiles, as well as the size and location of plants. The elements that characterize the configurations are as follows: each factory has its RESs; there is a shared RES between factories; an intermediate situation; the presence of intermediate exchange; and the presence of storage. Configurations that incorporate self-consumption and collective consumption result in the best results, especially when storage is present.
2.2.13. Greece
In [117], it is discussed how RES and REC projects also present psychological and social problems. The article presents a combination of the economic perspectives of RECs with ecological policy research on alternative economies. This leads to the concept of CREEs (community renewable energy ecologies) that could influence political decisions. Fundamental elements that must be considered are property, finance, labor, and infrastructure. Benefits, problems, and dangers of RECs are also reported, together with contributions connecting political ecologies with different economic perspectives. Specific ethical–political orientations in RECs are identified. Extending the development of RECs to these areas expands the possibilities of social experimentation beyond capitalism. In [118], they conducted a thorough examination of how a REC can facilitate the green transition.
2.2.14. Ireland
In the [119] study, it is discussed how wind exploitation potential in RECs depends on the availability of reliable wind data (diurnal and seasonal). A case study in Ireland is presented. The most reliable database among those examined was ERA5. The REC is equipped with microturbines from 300 W to 50 kW. No turbine is present in the cities. Unfortunately, reliable historical data are missing.
2.2.15. Austria
In Austria [120], the EU has promoted RECs and CECs in accordance with RED II, aiming to enhance energy efficiency, increase the integration of energy sources, and reduce greenhouse gas emissions through the production, storage, sharing, consumption, and sale of renewable energy. The paper also deals with the protection of personal data through blockchain technology. The model has been tested in Styria, Austria, and continues to be tested. In [121], despite the high potential of RECs, their development is currently hampered by the following limiting factors: during the planning phase, numerous variables (including the number and type of members and distributed technologies) must be taken into account. An optimal planning approach based on mixed linear programming is proposed. A case study in a village of the municipality in Carinthia (Austria) is presented, with six consumers and three prosumers, distributed photovoltaic systems, storage, different tariff scenarios, and reimbursement in the tariff. Energy cost savings of 15% and a 35% reduction in CO2 emissions are achieved. In [122], the authors present and discuss changes in Austrian legislation to accommodate the changes introduced by European law. As an advantage, it establishes a legal basis for E-control; as a disadvantage, it provides an energy subsidy not self-consumed in the RECs but supplied to the grid (it is counterproductive because it acts against the principle of maximizing the self-consumption of RECs). It can be an example for other countries.
2.2.16. Malta
The authors of [123] present five Maltese case studies, and for each one, the optimal storage capacity is defined, ranging from 10 to 57 kWh. Peak reduction is higher when storage is applied at the beginning of the day rather than at the end of the day.
2.2.17. Iceland
Authors in [124] present a case study of a community with difficulty in receiving energy due to the isolation of the glacial territory. The research considers how to obtain sufficient energy for a small village. PV and wind, with storage from batteries and underground facilities (for solar thermal energy), as well as hydrogen (from electrolysis and recovery from fuel cells), are considered as sources. Since the main industry is tourism, the maximum consumption is in July.
2.2.18. Croatia
The authors of [125] present a model to optimize the size of PV and BESS included in RECs. The model is validated with consumption data from Zagreb and Northern Germany. The model also evaluates how energy tariffs and prices influence the production and consumption profiles and thus the economic convenience. Constraints on the division of benefits may or may not be applied. If they are uniformly distributed, savings are not necessarily maximized.
2.2.19. Ukraine
Generally, Ukraine’s territory falls within the average zone in terms of solar radiation intensity. In [126], an energy-efficient solar system is considered combined with an external fence of an energy-efficient building. The authors of [127], dealing with RECs in Ukraine, assess that among RESs, PV is prevalent (in the ranges of 10–50 MW and 5–10 MW), followed by mini-hydro and wind, and biogas is growing. Thanks to the mix, the intermittency and variability of sources can be overcome. They mathematically model high-power systems that take electricity from RECs. The results highlight the importance of using different sources, taking into account the potential of the sources; the variability of electricity generation; and the operating costs. As a conclusion, it is imperative to increase the production capacity to cope with peak consumption, especially for biogas.
2.2.20. Denmark
Regarding energy citizenship and empowerment in RECs, in Denmark, the concept of “energy citizenship” is emphasized. Studies highlight Denmark’s mature policy support, cooperative business models, and community trust as key enablers of successful RECs’ activation (see Section 2.2 above [20,128] Section Portugal, Latvia, Norway, Spain, Brazil, Germany, France, Switzerland, and Benelux below).
2.2.21. United Kingdom
In the UK, RECs face uncertainty due to post-Brexit divergence from EU directives like RED II, despite a strong legacy of cooperative energy models [20,100]. Recent studies emphasize the role of RECs in addressing energy poverty but highlight the need for clearer regulatory support to sustain their growth and inclusivity [128,129].
2.2.22. Multiple Countries
Several studies involve multiple countries, as they explore not just the status of a single nation but also that of multiple nations in the EU.
Italy and Germany
The paper by [87] presents a comparative study of how the two countries incorporate RED II into their legal systems through the application of the multilevel governance principle, drawing on the results of the Horizon 2020 COME RES project. Although Germany is better suited to implement RECs, the conversion of RED II into law proved more laborious and fragmented. Common points between the two countries include a long tradition of cooperatives, federal policy systems, regions and municipalities enjoying a certain level of administrative autonomy, and EU decisions facilitated by local initiatives. On the contrary, the differences are that RECs in Italy are mainly focused on PV, whereas in Germany, cooperatives manage PV. However, due to a delay in implementing European directives, the REC foundation was also delayed. Political involvement is considered crucial for both countries.
Germany and The Netherland
In [130], it is assessed that the success of the REC initiative is greatly influenced by the social and institutional context in which RECs are activated. The focus of the paper is on the strategy for group formation, task distribution, collective action, communication, decision-making, and problem-solving strategies. RECs achieve their goals with the involvement of a few volunteers who act as free riders. The paper tries to answer the question “what factors influence the formation and organization of RECs?” through the analysis of theories on collective actions, group work, and fundamental initiatives on one side and the analysis of case studies (two in Germany and two in the Netherlands) on the other. It results that the formation and organization of RECs do not depend on the local situation (at least for the case studies in Northern Europe). However, it seems more important how intense the collaboration is between the founding members, as well as other intrinsic factors such as community size, the level of complexity, and the complexity of the adopted technologies. The study in [131] starts from the point that some countries (Germany and the Netherlands) have extensive previous experience in RECs, while others (Eastern European countries) have none. So procedures and situations in Germany and Bulgaria are compared through the related literature and interviews with experts. The difference is significant, although some gaps are also present in Germany. The study then focuses on providing tools for REC development in eastern countries, again through a comparison with Germany, a leader in the application of RECs. It results that the possibility of REC activation is more likely in wealthy countries. Legislative/economic support policies, as well as social factors (e.g., political support), are fundamental. In Germany, there are 1747 RECs for a percentage of RES of 40%, while in Bulgaria, the percentage is 21.6%. In Bulgaria, the electricity system is not yet completely liberalized (it is the last country in the EU). Thus, it results that factors promoting RECs include a supportive environment (including the national one), the country’s economic situation, financial support, a direct regulatory system, liberalization of efforts, and greater citizen involvement, as well as the removal of barriers stemming from the country’s previous history, such as socialism. In [132], the validity of transferring best practices from one state to another (from the Netherlands to Thuringia, Germany) is examined through a user’s questionnaire, in the context of legal, socio-economic, spatial, and environmental factors. The case studies include the transfer of experiences from the Netherlands to Thuringia, the transfer of the business model from Flanders to the Puglia region, and from Magliano Alpi to Latvia, as well as the transfer of the concept of Enercop (a Spanish energy cooperative) to the Canary Islands. Funding and a suitable participation format are essential. It is also necessary to establish clear objectives; to collaborate with local authorities, organizations, and citizens; to involve stakeholders in the planning and implementation of the project; to inform the community on the benefits of the REC project; to ensure REC sustainability; and to develop a business model directly designed for the REC members.
Portugal, Latvia, Norway, Spain, Brazil, Germany, France, Switzerland, and Benelux
The authors of [101] present a study on Latvia, Norway, Portugal, and Spain, discussing how energy justice is perceived and implemented in RECs. The study was conducted through interviews in the four countries that have adopted RED II. The analysis shows that RED II can actually contribute to economic, social, and environmental sustainability; however, the conditions for a democratic, transformative, and equity-increasing sustainability are still lacking. Therefore, these features are committed to individual countries through national regulation. The authors of [129] present a comparative study in Portugal and Brazil, which presents an innovative approach to the REC consumption forecasting model using ML and extreme gradient boosting. From it, designing an optimal REC management system is possible. They also report a case study in the UK. In [133], a 4-step funnel strategy is proposed and applied to three different RECs in Europe (Spain, Switzerland, and the Benelux region). Steps 1 is to identify a list of possible scenarios, integrate different technologies on demand-side management, reduce the load on the grid, and develop an energy exchange platform; in step 2 a list of all technologies available for the project is compiled; step 3 implements different level solutions, from the point of view of members, the community, and the federation; step 4 validates the scenario through appropriate PKIs (performance indicators). The inverted funnel approach, on the other hand, consists of the following: 1—actors (TSO, DSO, investors/owners); 2—goals/objectives; 3—boundary conditions; and 4—a business model. The study recommends cooperation between different RECs, even those located in distant areas.
Italy, Germany, Romania, Spain, Norway, Denmark, Denmark, and the United Kingdom
In [128] Italy, Germany, Denmark, and the United Kingdom, even if they all receive economic, environmental, and social benefits from RECs, technical, regulatory, and economic problems still persist. The research activities in this field by the Mediterranean Institute of Science and Technology are described in the paper. In addition to energy production and sharing, RECs also deal with energy efficiency, smart consumption, and synergies with other sectors, such as agriculture and transportation. According to RED II and RED III, emissions must be reduced by 55% compared to 1990, and renewables must be brought to 42%, or even 45% (RED II was at 32%). Related procedures should be simplified. Key factors include the following: in Germany, 200 energy cooperatives are present; in Denmark, cooperatives own 40% of wind turbines; and the primary goal of Great Britain is to combat energy poverty. The study by [105] examines how SMEs in four European countries (Germany, Romania, Spain, and Norway) perceive RECs. Factors encouraging people to join are the cost of energy, the presence of local suppliers, and the few problems with overall and demand-side management. On the contrary, lengthy purchasing procedures and the need for international suppliers can discourage them.
Additionally, how national laws establish the REC constitution rules is fundamental. The answers to these questions are obtained through the analysis of 823 questionnaires. The cooperative model is more preferable than private ownership. Additionally, long-term agreements with local renewable energy suppliers, leasing contracts for infrastructure, and services for aggregating SMEs when they are closely located represent an incentivizing factor. In [100] the authors discuss the political impact of RECS, as well as the decentralization and democratization of energy, in accordance with RED II. A proposal is made to recognize RECs as legal entities to promote the energy transition, particularly in the UK and the Netherlands. This is a way to suggest to Member States how to implement RED II. They propose an institutionally socio-legal approach to establish a civil energy network through RECs.
Eleven Baltic Countries
In [134], the 11 Baltic countries are divided into three groups: Nordic countries, Baltic republics, and Central and Eastern European countries. RECs help overcome the great diversity among different energy policies and define possible strategies at the national and international levels. Regional and sub-regional comparative analyses are conducted. Due to the significant differences between the three blocks of countries, three strategies are possible: countries rich in renewables must increase their grid endowment; others that have already expanded their grids could increase renewable source production; those that have been poorly involved in energy must be helped towards the energy transition and decarbonization.
2.3. America
2.3.1. USA
The authors in [135] propose a new sustainability index (SI), which is a function of load dispersion loss and an increase in RES use. It determines the optimal size and location of RES using social, economic, environmental, and technical considerations. It uses a model that takes into account the uncertainty and variability of renewables. The method is validated with a simulation. From this, it is demonstrated how RES planning and energy efficiency programs affect the SI. Wind and solar energy production in the city of Milwaukee (Wisconsin, USA) is simulated. The performance indexes in the adopted scenarios yield better results, but according to the authors, a total commitment to renewables is not advisable. The study by [136] handles how the integration of RESs in microgrids allows for the improvement of operational sustainability and resilience. The optimal generation and distribution of energy in response to real conditions can be achieved with advanced optimization methods (AI, ML, and IoT). The contribution of battery storage should be considered. The study by [137] describes a solar and wind microgrid for 10,000 houses in North Texas, which are supplied with hydrogen storage. Storage is the key factor to achieve a CO2 reduction of 87,000 tons.
In [138], the surplus of PV production is used to generate hydrogen by refueling. Credits are offered to compensate members who produce more, and backup batteries are included (container energy storage system, CESS). An intelligent system operates in three phases: 1—the REC determines the surplus energy available for H2 production; 2—a coordinator within the REC determines the carbon credits produced; 3—the REC sells the unapproved excess to the grid and allocates it to private consumers. The cost reduction obtained ranges from 11 to 29%, while production from electrifiers yields 3–4.7%, and consumption, thanks to batteries, ranges from 21 to 66%. Electric vehicles can be either battery-powered (for light vehicles) or hydrogen-powered (for mostly heavy vehicles). The case study presented is in Austin (Texas), where a tandem between H2 and the CESS is implemented.
2.3.2. Canada
A review study by [139] explains how indigenous involvement can contribute to the economy and management of RECs. The review demonstrates the need for collaboration among government, industry, and the public to achieve an effective energy transition and achieve self-sufficiency. Large-scale projects on PV, wind, biomass, and hydroelectricity are presented. The study is focused on the social impact of large RES installations, the lack of funds and decisions, community participation in decisions and agreement on benefits, the dominant role of the crown and top-down policies, informed consent and community involvement, commitment and ownership of equity, and maintenance of trust and relationships. For its part in [140], it is possible to see that in Canada, there are 635 RES development projects for a total of 28 GWs, all owned or co-owned by RECs. Clean energy objectives for different provinces in Canada are presented. Moreover, in [141], the authors explore the energy transition for Inuit indigenous people (redskins), leading to diesel reduction, job creation, income, community ownership, and growth of the local economy. Data show that RECs are a source of economic welfare for natives, as assessed by the CWB (Community Well-being Index). The underlying mechanism, however, still needs to be explored.
2.3.3. Multiple Countries: Canada and USA (North America), Brazil, Western Europe, and Korea
In a study [142] comparing Canada and Korea, six cases with local storage, community storage, internal exchange, and combinations among them are examined. A REC with five buildings, in various seasons, is modeled. The best solution is the combination of internal exchange and community storage (60% cost reduction compared to the no REC case). In [143], a remote location, not served by the grid, is simulated for Congo, Australia, and Canada, utilizing an off-grid REC in (PYTHON environment) in various scenarios. The optimum number of PV modules was 50 for Congo, 55 for Australia, and 150 batteries of 225 kWh for all. Substantial difficulties were found in Canada due to the variability of the climate, which includes many days without solar radiation. So in this country, wind, biomass, and mini-hydro are also suitable in addition to PV. Feasibility is also a function of the profit and loss statements in remote locations, such as those in Congo, Australia, and Canada. RECs can be a significant help in fighting energy poverty. Regarding Brazil, see [129] in Section Portugal, Latvia, Norway, Spain, Brazil, Germany, France, Switzerland, and Benelux for more details. An ML-based system was developed to forecast and manage electricity consumption in RECs, thereby enhancing energy efficiency and operational planning. The study by [144] explains how nature-based solutions (NbSs) can contribute to the success of RECs in fighting climate change. Procedural and distributive justice can overcome the difficulties encountered in applying NbSs.
2.4. Africa
2.4.1. South Africa
As of the beginning of 2024, 9000 RECs have been funded in the EU, with 5000 in Great Britain and 105 in Australia (community energy groups). Africa, however, is at a stalemate. The study by [145] examines five cases of RECs in Africa (South Africa, Malawi, Cameroon, Togo, and Ivory Coast), discussing their organization, including their management system, ownership, financing, composition, added value, and benefits to the local community, as well as the types of adopted RESs. It is urgent to start the dialog among the eight economic systems of Africa to develop RECs and reduce environmental damage. In [146], a study review of the available literature states that REC-enhanced access to energy is a measure to combat poverty, not just energy poverty. Two phases are described: 1—quantitative study from the net and 2—qualitative study from interviews. A case study in Soweto (Johannesburg district) demonstrates that the adoption of RECs can reduce poverty, enhance the socioeconomic status of citizens, promote economic growth, and preserve the environment. There is a need for government intervention to provide less well-off groups with PV panels or other RESs. The development of energy sources allows for better food security (refrigeration) and job opportunities and increases work productivity, particularly with RESs (according to the UN sustainable development goal). Then the study examines the connection between economic growth, poverty reduction, clean energy consumption, and the active involvement of citizens. According to the authors in [147], RESs represent an opportunity to increase the development of agricultural regions isolated from the grid (off-grid). PV, wind, and biomass can help the development of these areas through small-scale RECs in the rural context. The paper analyses the conditions for the socioeconomic feasibility of these solutions. In [148], after examining Congo, Tanzania, Kenya, and Mozambique, it is found that access to RESs is daunting, especially in rural areas, due to political factors. Overcoming this attitude brings significant advantages. According to current forecasts, only in 2080 will there be general access to electricity, and within a century from now, complete access to RESs can be achieved. Thus, the problem is whether all these efforts are worthwhile or whether it is better to invest in the socioeconomic improvement of people. In [149] the community’s participation in two renewable energy projects is evaluated: one involves mini-hydroelectric, while the other involves PV. Community participation was initially denied, while it was favored for the other. Finally, the latter project proved to be more sustainable. The acceptance by the community is therefore fundamental.
2.4.2. North Africa
The study by [150] examines how renewable energy projects can enhance the lives of people living in Africa. This, e.g., is a result of Morocco’s Noor Solar Power project. Additionally, the examination of policy interventions, intervention strategies, and capacity-building initiatives is also considered. Considering Africa’s poor electrification and the significant potential of renewables (solar, wind, biomass, and geothermal), the problems we face are insufficient funding, limited access to technology, a weak regulatory environment, and political instability. Nonetheless, future expectations are reasonable.
2.4.3. Uganda
In [151], the value of community involvement is considered, along with measures to encourage citizens to support REC projects through education programs, community leadership development, technology transfer, and information sharing. All these actions aim to promote the social acceptance of RECs.
2.4.4. Nigeria
In [152], a model of a village is developed, located at the University of Mewar, which is currently powered by fossil fuels. The model envisions an energy supply system comprising a hybrid PV (22%) and a wind (29%) source, both of which are integrated into the grid, to provide reliable, sustainable, and affordable energy. In the paper, the HOMER Pro software is used. As a result, the MG can export energy. A sensitivity analysis is conducted to assess the initiative’s robustness under varying weather conditions (sun and wind).
2.4.5. Kenya
In [153], a qualitative investigation of the mechanisms and motivations of land use for RESs within RECs is carried out. Drawing on data collected through interviews, the paper provides an in-depth examination of RES projects. Due to the complexity of the relationships between the various types of members, it is necessary to have adaptable strategies. In the sub-Saharan area, the majority of the 700 million people lack access to electricity. Both large-scale and small–medium-scale RES projects are examined. The large ones are more efficient but consume more land, and the small ones are directed at local needs of the territory, but they cannot change the overall situation. Then the problem arises from the lack of knowledge of land management needed for RESs on the part of the community and the leading authorities. Two case studies are the large wind farm of Kipeto and the small PV of the SEED lab. As a result, the following items are outlined: awareness of the roles, responsibilities of the REC members, and clarity on the available options and on the distribution of costs and benefits.
2.5. Asia
2.5.1. India
Regarding the REC and SG situation in Asia and India, the authors of [152] simulate a village model, and in [154] they focus on how to fight energy poverty in India, with easier access to RESs, contributing to decarbonization and ensuring a fair and sustainable future. Two case studies are presented: the Kusum Scheme in Bihar (PV in rural areas) and the Ujjwala Yojana (cooking gas for families). The importance of social policies is emphasized through subsidies for low-income families, skill development for market use, the use of non-energy-intensive electrical devices, and community models that ensure benefits for their members.
2.5.2. Pakistan
The study by [155] handles the problem of isolated buildings with no or little access to the electricity grid, as well as how RESs can solve or reduce it. The paper proposes a hybrid system (RES, batteries, and backup diesel generator). The cited case study is a remote village in Pakistan. The hybrid system costs one-third less than the pure diesel one and reduces CO2 emissions by 90%, resulting in an advantage. In [156,157,158], the authors evaluated the potential of RESs in SG considering demand response programs for energy and battery management in smart homes and optimized the energy bill costs, the peak-to-average ratio, and carbon emission.
2.5.3. Iran
In [159], a mathematical model from the citizens’ point of view is presented to optimize the use of RESs in RECs. Three scenarios involving wind and PV production are reported. Using the “customer cost function,” the optimal value and distribution of incentives are determined.
2.5.4. China
In [160] the authors propose a robust expansion plan based on an integrated system, taking into account the uncertainty of power generation and investors’ preferences. They built an expansion model to minimize the total investment cost. Then, considering the uncertainty of wind power, they develop a robust model in two stages. Finally, with the linearization of the McCormick model, the solution’s efficiency is improved, and the model is validated through numerous case studies. It is an efficiency improvement to reduce CO2 emissions. As a case study, a 6-bus system is presented. The system’s designs can modify the investors’ risks while also harmonizing the practical needs.
2.5.5. South Korea and Pakistan
A study by [161] discusses the sustainable energy support to developing countries. A hybrid PV/biogas system (90% methane and 6% CO2) is proposed for an off-grid community. In [162], the results of residential and non-resident building communities powered by PV, geothermal, and hydrothermal heat pumps are reported. Fifty-six separate residential buildings and two office buildings are considered. Thermal energy derives from geothermal and heat from sewerage. A 5% difference between the simulation and the real case is found. In Korea, the Green New Deal, similar to REDII/III, is active. In [163], a distributed energy system is presented, modeled by evaluating four possible scenarios. The case study is related to Jeju Island. The most convenient solution leads to a 10% increase in RES use, but other actions are evaluated to increase this percentage: carbon tax, incentives, and energy price. Storage increases the convenience of RESs by reducing peaks. Active financial support can increase the percentage of renewables.
2.5.6. South Korea and Canada
In [142], a combined study of Canada and Korea is reported; see Section 2.2.3 for details.
2.6. Australia
2.6.1. Australia
In [6], a comparison is carried out among the rules of the three regions, Europe, Australia, and New Zealand, regarding the regulatory model of the energy market and the relative importance of RESs.
Australia has great RES potential: wind in the south, tides in the north, geothermal in the center and southeast regions, and photovoltaic everywhere. It could produce 50% of the electricity in 2025 and 100% in 2030 from RES. The target for 2020 was 23%. New plants must be built and incentivized, but infrastructures must also be adapted (e.g., the electric grid). According to the “National Community Energy Strategy”, REC models suitable for the diffusion and maintenance of their characteristics must be developed and maintained; that is, innovation should possibly be scaled, replicated, and promoted. The situation in 2017 was 259 TWh (15% renewables of which 35.6% were from hydroelectric, 32.4% from wind, and 8.8% from photovoltaic). Tasmania, with 87% (all hydro), and South Australia, with 43% (mostly wind), were the regions with the most significant RES development. From a legal point of view, the Renewable Energy (Electricity) Act 2000 and the Renewable Energy (Electricity) Regulations 2001 were promoted; small-scale and large-scale plants are divided, and the relative certificates are issued. Australia does not forecast RECs, but other forms of aggregation are used: public companies with shares, cooperatives, incorporated associations, and trust companies. Cooperative members must be active. In [164], virtual power plants with REC management systems facilitate the energy transition by mitigating the impact of distributed generators and adding value to prosumers. Through a reported case study, the effect of virtual plants on RECs with RESs and storage is evaluated. In the case study, CO2 emissions are reduced by 50–70% over 10 years. Even if the environmental benefits are not relevant at the moment, they will become so in the future. In [165], researchers studied how RECs can be protected against and prevent natural disasters, such as floods, using hydroelectric power. In [166] (Fiji Islands, Oceania), implementing RECs in small islands is explored. Three case studies were analyzed: a grid-connected secondary school with rooftop PV, an off-grid community with home solar, and a farm using PV for irrigation. Seven perspectives are enhanced: human, social, cultural, financial, natural, constructive, and political. Therefore, it improves the resilience of island communities, in particular to disaster risks, which are common in those areas.
2.6.2. New Zealand
According to [6], New Zealand is one of the leading countries in RESs (80% renewables in 2019, with a target of 100% in 2035, of which 60% is hydro, especially in the south, and geothermal in the north). From a legal perspective, the Electricity Industry Act [167] has been in effect since 2010. It establishes the rules for RES production, energy sharing, and financial support. However, there is no specific reference to RECs in it. Mechanisms for trustees (e.g., the Trustee Act) act for the convenience of specific groups of members. Consequently, the number of trustees per capita is among the largest in the world, even though many are family-run. Both “community trust” (producers) and “customer trust” (consumers) are present. Two-thirds of the distribution network is owned by trusts of electric cooperatives, with significant participation from public administrations. The Maori tribes own some trusts and manage some small local projects.
Following Table 1 and Table 2 that present a classification of reviewed studies by country and continent, along with the associated technologies and the number of review articles identified, are reported.
In total, 173 research papers and related work are studied. A total of nine review papers are identified, which are similar but not as comprehensive as the present review. This review provides a comprehensive examination of the evolution and implementation of RECs, with an emphasis on EU regulatory frameworks (RED I, II, and III), the technologies employed, governance structures, and socioeconomic impacts. It includes case studies from Europe, Asia, and Africa, highlighting roles, activities, benefits, and the associated challenges faced by RECs across different contexts.
3. Covered Technologies
3.1. Solar PV
Studies that have modeled and simulated RECs integrating solar PV technology systems are discussed one by one. For example, ref. [10] simulates a REC consisting of five MGs, each equipped with PV systems and battery storage. In [168] PV with wind is used; in [15] the PV field is studied, and in [15] a REC with 100 members jointly owning 100 kWp plants is studied, while [17] explores the economic aspects of photovoltaic deployment. The diffusion of rooftop PV is discussed in [26,28,35,49], which focus on PV integration in residential settings. The study by [53] analyzes homes with rooftop PV, heat pumps, and both electric and thermal storage, whereas [43] deals with the use of heat pumps and PV systems. In [60], PV panels installed on school rooftops exchange energy with nearby residents. Reference [64] provides an economic analysis on PV systems. Sensitivity analyses on PV size, member numbers, and economic impacts are presented in [67]. According to [70], the optimal solution involves PV powering heat pumps. PV system sizing within RECs is addressed in [76], and [77] highlights the key role of PV with respect to other RESs. Rooftop PV potential to transform new and existing buildings is discussed in [80], while [81] investigates how uncertainties in PV production and consumption affect REC performance. Further studies include [86], which examines PV and BESS in German multi-family buildings, and [89], which focuses on sharing and selling PV-generated electricity. Net billing for PV systems is cited in [102], and city-level PV incentives are studies in [104]. PV plants to be used for water treatment are presented in [106], and strategies to maximize PV profits are shown in [107]. Household consumers owning PV, electric vehicles, batteries, and heat pumps are studied in [114], while optimal PV and BESS sizing for RECs is explored in [125]. Photovoltaic adoption is also discussed in [87,121], while [154] investigates PV use in rural areas. The combination of PV with other RES is covered in [162], and [138] explores the use of PV surplus for hydrogen production by means of refueling stations. The study in [166] examines off-grid communities using rooftop PV for home and farm irrigation purposes. In [126] the technical characteristics of the proposed solar collector’s heat are analyzed to assess its suitability for subsequent installation and application by consumers.
3.2. Wind
Studies on wind energy adopted by RECs highlight its significant potential and integration challenges. For instance, refs. [119,128] discuss the exploitation potential of wind energy for RECs. The large-scale wind farm of Kipeto is analyzed in [153], demonstrating the impact of substantial wind power projects. Additionally, ref. [159] reports combined wind and PV production within RECs, while [160] addresses the uncertainties associated with wind power generation.
3.3. Hydrogen
3.4. Biogas
Renewables like biogas, sewage, and geothermal energy, along with local heating via thermal panels, are discussed in [103]. To meet peak demand, production capacity must increase, especially for biogas, as emphasized in [127]. A hybrid PV/biogas system (90% methane, 6% CO2) for off-grid communities is proposed in [161]. The main factors influencing methane formation are studied in [169], and the calculation of biogas production is presented. The productivity of the bioreactor is determined depending on the temperature of the raw material and the hydraulic retention time.
3.5. Hybrid Mix RESs
Hybrid renewable energy systems combining PV, wind, biomass, and other sources are widely explored. For example, in [168], hybrid RES systems (PV and wind) are evaluated with the LCOE (levelized cost of electricity) index. In [19], a system to produce renewable energy by wind, solar, and biomass using H2 as storage is described. In [11], hydroelectric, wind, thermo-oceanic, water movement in the sea (tides and waves), solar thermoelectric, PV, and surface geothermal energy are explored, as well as 1000 kW of PV and 2.1 MW of the biomass Rankine cycle in [37]. In [38], solar and photovoltaic systems, with integration of LPG boilers for heat generation, are treated, while in [103], the centralized use of renewables (biogas, sewage, and geothermal) or local heating with thermal panels, PV, heat pumps with geothermal energy (GSHP) is studied. The study by [106] discusses the Kněžice situation characterized by a municipally operated CHP plant, Hostětín (240 inhabitants) by biomass and solar, and Dolní Lhota by a PV plant to be used with a wastewater treatment plant. In [110], wind and hydro are handled, as well as PV and wind, with storage from batteries and underground facilities (for solar thermal energy); hydrogen (from electrolysis and recovery from fuel cells); and biogas in [113]. In Ukrainian RECs, PV is prevalent (in the ranges of 10–50 MW 5–10 MW) [125], followed by mini-hydro and wind; biogas is growing. In [135], wind and solar plants are described, and in [137], a solar and wind MG for 10,000 homes in North Texas and hydrogen storage is described. In [139], large-scale projects on PV, wind, biomass, and hydroelectricity are presented. The study by [142] discusses how wind, biomass, and mini-hydro are suited to be added to PV, while [147] explains how PV, wind, and biomass can help the development of RECs. The authors of [149] presents two renewable energy projects: one involves mini hydroelectric, and the other involves PV. In [150], the huge potential of renewables (solar, wind, biomass, and geothermal) is outlined. In [152], hybrid PV and wind are described, and in [153] the wind farm of Kipeto and its small PV are discussed. In [159], PV and wind are discussed, and in [161], a hybrid PV/biogas system (90% methane and 6% CO2) is proposed for an off-grid community. Moreover, in [162], results of residential and non-resident building communities powered by PV, geothermal, and hydrothermal heat pumps are reported. In [6], the authors describe the Australian RES potential: wind in the south, tides in the north, geothermal in the center and southeast regions, and photovoltaic systems everywhere.
3.6. Storage and Type
The role of storage systems in enhancing the operation and self-sufficiency of RECs and CECs are discussed in several studies. In [9], storage is declared as a crucial component of operational activities, and in [19] hydrogen storage is important, while [28] highlights the integration of electric cars, heat pumps, and battery storage in community systems. The use of a PV plant combined with lithium-ion batteries for balancing services is examined in [10], and ref. [12] emphasizes the importance of community storage and electric vehicles. The study by [168] explores the potential of storage through different methods, like hydro re-pumping and hydrogen production from PV and wind systems. Hourly based simulations involving lithium-ion batteries are also presented in [28]. In [53], thermal storage used for flexibility improvements through BESS is discussed. The authors of [44,66] consider BESS deployment in seaports for energy improvement and excess storage. In [63], the use of hydrogen for storage is considered. The sizing of BESS to evaluate REC potential is addressed in [72], and ref. [74] identifies BESS as fundamental to achieving self-sufficiency. The study by [116] discusses collective battery systems as a means to store excess energy, contributing to REC self-subsistence. The authors of [137] describe a RES MG for 10,000 homes in North Texas with hydrogen storage. Additionally, ref. [138] explores the integration of battery-powered vehicles and REC engagement through refilling stations.
4. REC Procedure and Application
4.1. Modeling and Management
The following studies present simulation, modeling, and management frameworks for RECs: ref. [10] for a model, ref. [11] for management, ref. [12] for the simulation model, ref. [13] for the mathematical model and management, and [14,15,16,168] primarily focused on modeling. In contrast, works like [17] focus on management, while [23,24,26] emphasize the management dimension.
Integrated perspectives that combine modeling and management are evident in studies such as [36], which discusses methods and tools for modeling distributed energy resources along with REC management strategies, and [45], which addresses prototyping, implementation, and management practices. Similarly, refs. [47,82] explore management modes and technical–economic analysis for RECs. Several other contributions provide detailed models and simulations, including models by those in [52,55], management in [54] model, modeling and optimization in [63], and the REC conceptual model in [68]. Ref. [91] deals with management and governance, while ref. [92] presents an optimization model, and ref. [93] focuses on the analysis. Reference [94] focuses on the optimal sizing.
Noteworthy hybrid and applied approaches can be found in [96], which focuses on management/models; in [99,104,107,110,111,112,114,116,120,121,124,133,135,136,142,143,152,159,163], which focus on models; in [127], which focuses on a mathematical model; and in [129], which focuses on a forecast model. At the same time [102,103,108,115,117,148,150,151,161] are related to management. Ref. [162] is a real case model, and [67] is a business model. Additionally, ref. [91] highlights considerations about management and governance, and [95] outlines the development of a home energy management system. Together, these studies illustrate the diversity and depth of modeling, management, and integrated approaches employed in the design, operation, and optimization of RECs.
4.2. Real Case Studies, Project Report, or Existing
4.3. Laws and Regulations
Studies such as [2,3,100] discuss regulatory frameworks, with a particular focus on EU regulations like RED II and RED III. References [4,5] address low-carbon initiatives, while [6,7,9,19,161] explore laws and legal aspects related to energy communities and sharing mechanisms. Reference [33] provides policy advices to transpose new European rules about renewable energy communities, and [55,58,167] further elaborate European legislation, existing policies, and the socioeconomic and legal conditions necessary to establish RECs. Guidelines that can be adapted to various contexts are discussed in [58], whereas [77,78] examine the political, regulatory, and socio-political environments. The influence of policies on governance and management is emphasized in [85,89], and procedural aspects are addressed in [144]. In [84], the Austrian and Italian regulations are discussed.
4.4. Public and Community Awareness
Public awareness is crucial for REC success, as highlighted in [62], which emphasizes the role of local public authorities and trust. In [78], the authors discuss socio-political control and social acceptance, while ref. [153] stresses the importance of clarity on REC roles, responsibilities, and available options in Kenya.
5. Review Articles
The articles identified as reviews and referenced in the present review study are [22,23,24,25,31,44,139,140,144]. For what the discussion about RECs concerns, three points of view are present: type of source (fossil or renewable), configuration of supply (centralized or distributed), and type of prosumer (individuals or communities) [170]. Given the intent of clarification of the purposes, it is appropriate to distinguish between the advantages of one source compared to another, of one configuration compared to another, and of certain types of prosumers compared to others.
6. Roles, Activities, and Purposes of RECs
This section describes the roles, activities, and benefits of RECs as explored in the recent literature. It provides a concise interpretation of case studies, experimental results, and theoretical analyses across various countries, highlighting the technical, socioeconomic, legal, and policy aspects associated with REC implementation. Figure 1 shows the implementation of a REC with open and voluntary participation, steps, and core advantages.
6.1. Role and Transformation of RECs
RECs play a transformative role in fostering the energy transition, fighting climate change by promoting local renewable energy production, enhancing grid resilience, increasing social equity, and enabling active community participation in sustainable development. According to [18], the new version of RED III aims to increase RESs to 42.5% by 2030, with a target of 45%, covering transport, industry, and buildings. To achieve it promptly, it needs to speed up the process of the REC organization and clearly define its roles. Reference [56] discusses the progress and role of RECs in the Italian city of Assisi, emphasizing the pivotal role of the public administration. The analysis considers technical, economic, and energy aspects. In [144], in North America and Western Europe, the authors suggested that NbS can contribute to the success of RECs in addressing climate changes. At the same time, ref. [134] studied and divided regions into three groups: Nordic countries, Baltic republics, and Central Eastern Europe. According to them the RECs are valuable due to the diversity of energy policies across regions, helping to define national strategies. The authors of [57] assess the socioeconomic and legal conditions to establish RECs under the current legislation, identifying risks and benefits of creating new professional profiles for this market. The limited number of RECs so far has hindered the creation of general guidelines. Even if the local market shows interest, the advantages must still be fully understood. Interviews and literature reviews indicate that despite existing studies, there is still a need to gather a broad consensus. In Italy, a lack of clarity from the administrations persists. The study by [58] presents strategies to implement a network of small villages in the Madonie area (Sardinia) to ensure their sustainability. Guidelines developed here can be applied to other contexts. The study by [93] analyzes the energy-sharing coefficients proposed by the Portuguese authority. It finds out that variable coefficients are more beneficial for large consumers, while fixed coefficients are better for small consumers. Ref. [84] shows that RECs present a good opportunity to alleviate grid overloads, but European tariffs remain a barrier. A case study demonstrates a potential peak reduction of up to 50%. The study by [94] suggests that MOPSO can be used to evaluate optimal strategies in RECs, and four case studies with different energy strategies are analyzed. In [59], the Horizon Europe KNOWING project is analyzed, and the effect of RECs on urban architectural design is explored, emphasizing the importance of integrating REC components (panels, canopies, pylons, and charging stations) into the urban context. The role of renewable energy is outlined in [159], presenting a mathematical model from the citizens’ perspective to optimize RES use in RECs. Using the “customer cost function,” the optimal value of incentives is determined. The study by [155] addresses the issue of isolated buildings’ RECs with limited or no grid access, proposing a hybrid system of RESs, batteries, and a diesel generator backup. It is shown that the hybrid system costs one-third of a pure diesel system and reduces CO2 emissions by 90%, making it a viable solution in RECs. In [133], the authors study a four-step funnel strategy model, and it is proposed and applied to three RECs in Europe (in Spain, Switzerland, and Benelux). The study proposes a stepwise framework for developing renewable energy communities, identifying scenarios with DSM and energy exchange platforms, listing available technologies, implementing multi-level solutions (member, community, and federation), and validating them with PKIs. An alternative inverted funnel model starts with actors, sets goals, defines boundaries, and builds the business model. The study recommends cooperation between RECs, even across large distances. Complementing the REC transformation economic aspect, ref. [60] explores municipal REC models in Italy, where PV panels installed on school rooftops enable energy sharing with nearby residents. Their techno-economic evaluation under various scenarios reveals strong investment potential, with a 20-year NPV, as seen in detail in Section 2.2.1. This reflects the dominant Italian trend of small-scale RECs (≤100 kW) involving less than 100 participants. The authors of [101] investigate how energy justice is perceived and implemented via RECs (organized as suggested by RED II) through interviews. The study finds that RED II can promote economic, social, and environmental sustainability, but democratic, transformative, and equity-focused sustainability depends on national-level implementation.
Moreover, storage plays an important role in RECs as outlined in [123], which presents five case studies showing the optimal storage capacity for each, ranging from 10 to 57 kWh. Greater peak reduction is achieved when storage is used earlier in the day. In [161], the authors explores the results of sustainable development adopting an off-grid community initiative as a hybrid PV/biogas system (90% methane, 6% CO2). Meanwhile, ref. [61] shows an overview of REC design platforms in Italy under RED-II, categorized into four areas: input, output, optimization, and openness. While input and output are generally present, optimization and openness are lacking. The authors of [79] are focused on maximizing collective self-consumption in RECs, which is essential for reliability, but the lack of efficient systems of measuring consumption and loads presents a risk. The article proposes an AI-based method to extrapolate hourly loads from monthly consumption in three steps: identify a typical consumption pattern, input it into a random forest model, and generate hourly load trends. The model yields consumption forecast errors of 20–26% for hourly loads, 8% for monthly loads, and 0.12% for annual loads. In [151], researchers highlight the importance of community engagement in REC projects, including education programs, leadership organization, technology transfer, and information sharing, all crucial items for social acceptance. The study by [129] introduces an innovative REC consumption forecasting method using machine learning and extreme gradient boosting, aimed at developing an optimal REC management system. In [142], the authors compare six scenarios involving local storage, community storage, internal exchange, and mutual combinations for a REC with five buildings across various seasons. In [149] the researchers evaluate community participation in two renewable energy projects (mini-hydro and PV). In one project, community participation was excluded, while in the other it was encouraged. The latter proved to be more sustainable, showing that community acceptance is fundamental.
6.2. Main Activities of RECs
RECs’ engagement in a broad range of activities aims at promoting local, clean, and participatory energy systems. Their core functions primarily involve the generation of renewable energy, mainly through solar PV, wind, biogas, and small hydro installations. These actions complement energy storage, distribution, and self-consumption. Additionally, RECs facilitate peer-to-peer energy sharing, collective investment and purchasing, and energy efficiency initiatives. Many communities also produce education and awareness programs to foster citizen engagement, SMEs, as well as to reinvest profits into local development or social projects. Through these integrated efforts, RECs empower local actors to manage their energy production and consumption, thereby contributing to environmental sustainability and regional resilience. In Italy, RECs play an active role in making energy cleaner, more local, and more community-driven. From this perspective, it results that SMEs studied in [62] lack knowledge and experiences even if they are interested, hence the fundamental role of PAs. In Lombardy, despite the incentives and efforts of PAs, RECs have not yet taken off. It is therefore a question of increasing the level of knowledge about RECs within SMEs. In [97], it results that the efficiency of REC management depends on the ability to predict consumption. The authors do this through ML and provide a cluster-based solution for 24 h. This forecasting model, integrated with machine learning techniques, improves energy consumption within RECs. The study by [160] accounts for uncertainties in power generation and investor preferences. A two-stage optimization step using a linearized McCormick model improves efficiency and reduces CO2 emissions. In [81], it is reported how an uncertainty in PV production, together with that of consumption, can influence the balance sheets and performances of PV-based RECs. In the paper, a model with 10,000 production profiles, with a 50 kWp plant serving 100 residential consumers, is developed. The relative uncertainty is around 2–3%. There is an overestimation of the energy produced during the highly productive months, which demonstrates the need for statistical evaluation. The authors in [150] studied how renewable energy projects can improve the lives of ordinary people through policy intervention, effective strategies, and capacity-building initiatives. They consider Africa’s poor electrification and the huge potential of renewables (solar, wind, biomass, and geothermal). Identified problems in making effective RECs are insufficient funding, limited access to technology, a weak regulatory environment, and political instability. Beneficial purposes and key activities of RECs are discussed in [22]. European countries are at different stages of development in activating RECs according to RED-II. Three types of energy communities are discussed: HEC (homogeneous), MEC (mixed), and SEC (self-sufficient), depending on the total net energy. According to what was mentioned, Germany had more than half of the RECs in Europe in 2020, followed by the Netherlands and Denmark. The main barriers to wider expansion are bureaucratic obstacles, unwillingness of potential customers, economic and social obstacles, regulatory and legal uncertainties, and political, financial, and technical problems (grid barriers and losses, deteriorated voltage profiles, and high losses on lines). From a management perspective, ref. [102] presented energy cooperatives and showed how they can contribute to the exploitation of renewables, using a shift from net metering to net billing. All consumers (with their generation systems), producers (with PV covered by net billing), and prosumers (in cooperation with cooperatives) enjoy significant cost reductions. By their own energy clusters, CECs aim to increase energy self-sufficiency to combat energy poverty. In terms of RECs, activity efficiency, and reliability of REC activities on integrated energy systems and storage, ref. [19] explores the involvement of hydrogen storage in various renewable sources systems (wind, solar, and biomass) and shows excellent performance figures: 46% for economic reliability, 41–53% for operational efficiency, and 95% for distribution reliability. In [163], models of the distributed energy systems under four scenarios are presented. The optimal model includes a 10% renewable energy share, but mechanisms like carbon taxes, incentives, and storage increase viability.
Active financial support is the key to improving RECs’ adoption. Considering this, the techno-economic analysis of a hybrid MG system for a rural Indian village (University of Mewar) presented in [152] was carried out with the HOMER Pro software. The hybrid system integrates 22% PV and 29% wind energy with the existing grid to deliver reliable, sustainable, and affordable electricity. Sensitivity analysis confirms the design’s resilience under varying climatic conditions. In [63], through a techno-economic dataset, hydrogen storage-based MGs in Italy are explored. The result emphasizes hydrogen as an alternative to batteries, calling for a centralized database to manage the variability in model outcomes due to the lack of reliable data on electrolyzers, fuel cells, and other components. In the economic analysis of [64], PV systems within RECs are focused on sustainable urban development. Using discounted cash flow and net present value (NPV) methods, it evaluates investment profitability under different subsidy and market scenarios, finding PV-based RECs highly profitable with a low risk. The study proposes two innovative profit distribution models: one incentivizes energy-efficient behavior via lower trading prices, and the other promotes income equity by supporting lower-income households.
According to [136], integrating RESs into MGs in the U.S. significantly improves operational efficiency, sustainability, and resilience. Regarding demand-side management and the distributed energy utilization process of RECs, the study by [75] confirms the utility of integrated supply- and demand-side management to achieve high renewable shares at the lowest costs, further reinforcing the findings from [163]. The study by [80] investigates shared energy systems in RECs using rooftop PV installations. A Monte Carlo simulation of a 60-member community with 150 kWp total PV capacity shows that east- and west-facing panels can perform comparably or even better than south-facing ones due to the more balanced energy sharing patterns. In [128], the broader context of RECs in Italy, Germany, and Denmark is presented, highlighting their activity and role in addressing energy poverty and implementing RED II directives through cooperative models. In [146], it is discussed how REC-enhanced access to energy can fight poverty, as well as energy poverty. RECs can reduce poverty, improve the socioeconomic status of citizens, promote economic growth, and preserve the environment. The need for government intervention to provide less well-off groups with panels or other resources is evidenced. The development of energy sources allows for better food security (refrigeration), job opportunities, and increased work productivity, in particular with RES (according to the UN sustainable development goal). Then the study examines the connection between economic growth, poverty reduction, clean energy consumption, and the active involvement of citizens.
6.3. Benefits of RECs
RECs offer diverse and far-reaching benefits that extend beyond mere energy production to encompass environmental dimensions, clean energy production, and economic and social advantages. These benefits have been rigorously studied across various geographical and contextual settings, from urban districts in Europe to remote off-grid areas in Africa, Asia, and the Americas. The authors of [65] suggest reducing greenhouse gas emissions by mixing methane and 10% hydrogen. To assess multiple de-carbonization strategies, the authors of [70] conducted a detailed case study. Their findings indicate that heat pumps powered by PV and solar thermal systems offer the most sustainable and economically feasible pathway to RECs. They also point out the link between the insertion of hydrogen into methane and the greenhouse effect. On the topic of self-efficiency, the authors of [66] evaluated RECs in energy-intensive maritime ports, using a numerical model to assess solar- and wave-based generation coupled with battery storage. Their case study of the Port of Naples showed that up to 60% of the electricity demand can be satisfied, and 90% self-consumption can be achieved, with potential savings of EUR 5 million over 20 years and a payback period as short as 2–4 years for smaller installations. In terms of economic benefits, ref. [67] proposes a business model framework that highlights how the number of REC members and PV system size directly affect the economic outcomes. A demonstration of sector-coupled clean energy scenarios was addressed in [109], demonstrating the economic effectiveness of the updated electricity tariff framework and the potential shift from static to variable energy-sharing coefficients within LECs. They demonstrate that dynamic energy allocation increases self-consumption and reduces energy costs, particularly when it is coordinated with time-sensitive tariffs. In remote regions with off-grid RECs, such as Congo, Australia, and Canada, ref. [143] emphasizes the potential of RECs in alleviating energy poverty. The use of simulation tools helps to identify the optimal configurations, highlighting specific challenges to colder climates like Canada, where solar is less effective. The authors of [68] emphasize the conceptual model of RECs within a circular economic structure, highlighting that successful REC implementation depends on balancing member participation and PV capacity to avoid benefit saturation, attracting high daytime users for optimal energy sharing, and obtaining positive cash flows for community development. In Germany [85], the study quantifies REC benefits for residential prosumers, demonstrating how energy costs and tax reductions work even under volatile market conditions and favorable renewable energy policies. Similarly, ref. [154] examines the energy poverty reduction strategies through community models and inclusive policies, like the Kusum Scheme and Ujjwala Yojana, highlighting the importance of subsidies, skills development, and access to low-energy appliances.
In exploring abundant energy utilization through geothermal exploitation, the authors of [69] identified the most suitable areas in Italy for geothermal-based RECs, focusing on both thermal and electric needs. Their simulations demonstrate how geothermal energy could satisfy up to 49% of the total energy demand while combating energy poverty. In [71], a mixed-use REC is assessed, consisting of residential buildings, a university, and tertiary services. The study concluded that aligning community members with similar energy profiles enhances surplus energy sharing and system efficiency. Other studies underline the diverse benefits and challenges of RECs across different regions. In [153], large- vs. small-scale projects revealed trade-offs, emphasizing local governance and fair cost–benefit sharing. RECs differ in source, structure, and member type, and understanding these variations is an important key to maximizing their impact [31]. In [44], it is assessed that coordinated battery storage boosts grid flexibility and user benefits in RECs, while in [127], a mathematical model is developed, where high-power systems take electricity from RECs. RECs play a crucial role in accelerating the ecological transition by fostering local participation, enhancing energy autonomy, and promoting sustainable energy generation aligned with climate goals. By enabling decentralized production and consumption, they reduce transmission losses and empower citizens to contribute actively to decarbonization efforts. The results highlight the importance of integrating diverse energy sources while considering their potential, variability in electricity generation, and operating costs to reduce peak demand. Virtual power plants equipped with REC management systems further ease the energy transition by mitigating the impact of distributed generators, adding value to prosumers’ energy production, improving environmental and economic outcomes, and lowering the risk of energy-related disasters [118,164,165]. Figure 2 summarizes the leading roles, activities, and core value advantages of RECs. It highlights the key roles, e.g., of producers, coordinators, and data managers; core activities such as energy generation, sharing, and SG integration; and the resulting community benefits like cost savings, energy autonomy, job creation, and reduced emissions.
7. Special REC Configuration and Applications
Europe has become a pioneering continent for the deployment and evolution of RECs, offering a diverse range of examples that illustrate different models, directives, strategies, and challenges across countries. The following section highlights several representative applications in terms of thematic focuses of technological and experimental nature.
7.1. Technological and Optimization Approaches in Italy and Spain
Considering technological optimization, the authors in [28] modeled retrofit scenarios in order to involve condominiums in joining energy communities in Italy. Their approach is focused on optimizing renewable energy systems and storage integration, with results indicating high potential for energy autonomy and CO2 reduction. They developed a techno-economic model focused on retrofitting a multi-apartment condominium in Italy, a member of a REC. The analysis explores various technology retrofit scenarios, including the integration of PV systems, BESS, heat pumps, and building envelope improvements. Using simulations, the study evaluates the impact of each scenario on energy performance, self-consumption rates, economic viability, and carbon emissions. In [29], a game-theoretic approach to energy sharing in Italian RECs is proposed, with the goal of enhancing fair distribution and local job opportunities. Moreover, in [52], a MILP model is applied to optimize demand-side management among residential users, significantly increasing self-consumption and energy sharing. In Spain, ref. [106] used a genetic algorithms to optimize energy sharing among 128 prosumer families in Barcelona. Their results showed that strategic grouping based on consumption patterns can maximize self-consumption and reduce CO2 emissions. The authors of [49] provide a roadmap for the design and monitoring of RECs in Catania (Sicily), demonstrating that up to a 38% reduction in CO2 emission can be obtained and over 50–67 families can be financially supported.
7.2. Community Engagement, Governance, and Business Models
Communities’ and citizens’ motivations and dilemmas to join RECs are explored in [39] through a survey-based study in Italy. Their findings emphasized the importance of clear benefits and local identity in participation decisions. In [112], the economic efficiency of RES is evaluated, considering the effect of electricity tariffs, the ratio of heating and transport between electric and fossil sources, the price of renewable sources and storage, and the prices of internal electricity exchange. A total of 156 plausible scenarios are presented, with relative factors such as CAPEX (capital expenditure), tariffs, and investments. Capacity- and volume-based tariffs are more important, with the former being predominant. Moreover, ref. [42] introduces a decision-support tool to integrate RECs into municipal planning in Italy, demonstrating its utility for strategic urban energy planning.
7.3. Cross-Border, Remote, and Island Communities
Around the globe, some cross-border and island case studies are discussed in [21], which presents the benefits of cross-border RECs at the distribution level, especially in improving grid stability and socioeconomic cooperation in border regions.
In [35], the authors examined Pantelleria Island, showing how RECs can support local decarbonization strategies while mitigating financial risk. In [122], the authors analyze five RECs in Malta, highlighting the role of optimal battery sizing (10–57 kWh) for peak load reduction. Moreover, ref. [123] discusses a renewable transition in Flatøy, Iceland, showing how storage integration helps to address Arctic-specific energy challenges.
7.4. Advanced Forecasting, Tariff Design, and Energy Management
Considering the technological and uncertain nature of RECs and SG, the authors of [101] introduce a machine learning-based system to forecast electricity consumption in RECs, using boosting techniques with extreme gradients to improve system efficiency. In addition, the forecasting algorithms mentioned in [36,79] predict loads; ref. [82] considers forecast uncertainty and production; ref. [96] estimates consumption, and ref. [114] predicts future consumption, and [101] provides a comprehensive consumption forecast. In [83] the authors explored the impact of electricity tariff structures in Germany, finding that inappropriate tariffs can undermine REC performances even when technical potential is high. Ref. [120] applies mixed-integer linear programming for REC optimization in Austria, enabling strategic planning of energy generation and consumption.
7.5. Transnational Learning and Model Transfers
The intercontinental model transfer described in [132] documents the transfer of multi-functional energy garden concepts from the Netherlands to Thuringia (Germany) and other regions. This transnational case illustrates the need for adaptation to local needs, strong stakeholder involvement, and funding mechanisms.
8. Discussion and Future Directions
The future of RECs lies in advancing from pilot projects to mainstream, scalable models that integrate technical innovation with inclusive governance. In addition, a crucial issue is the socioeconomic impact and assessment on national economies, so there is a need for longitudinal studies assessing the broader socioeconomic impacts of RECs, including the green energy transition, job creation, local investment, energy poverty alleviation, and behavioral change. These insights can guide the optimization of REC structures and justify public support. In Appendix C, the renewable energy sources’ share in EU energy is shown in Figure A2, and REC deployment based on data from Eurostat is shown in Figure A3 [171,172]. Moreover, the author of [173] discussed a vital enabler of the clean energy transition, especially amid the ongoing energy crisis. The study conducts a comprehensive economic feasibility analysis of RECs under two primary investment strategies, namely (1) third-party investment and (2) self-investment by households, while integrating multiple cost allocation methods (flat pricing, time-of-use, and segmented pricing). Their optimization model reveals that third-party investments become profitable with suitable energy pricing, and it has a 15-year payback period, delivering a ~50% return on investment. Even when households select different pricing models, the third party’s profit drops only slightly (EUR 305), yet it enhances household participation incentives. On the other hand, joint self-investment yields the highest long-term benefit for local members, eliminating third-party profit margins, though it requires overcoming high upfront costs. Moreover, the RECON simulator [82], which was developed by ENEA, is a valuable tool for researchers and practitioners working on RECs, both for existing and planned projects. It supports comprehensive economic analysis, lifecycle assessments, cost management, and payback period evaluation.
Based on the reviewed papers, the following key directions can globally guide the continuous development and impact of RECs:
- a.
- Regulatory Harmonization and Policy Support
Future efforts must focus on refining and harmonizing national regulatory frameworks in line with EU directives RED II and RED III while also supporting non-EU countries in creating enabling environments. This includes clear definitions of REC entities, licensing streamlined procedures, and long-term financial incentives to ensure market viability.
- b.
- Integration of Smart Technologies
The adoption of SGs, blockchain, artificial intelligence, ML, and IoT technologies can significantly enhance the operational efficiency of RECs. These tools support real-time energy management, peer-to-peer trading, and demand response mechanisms that are essential for dynamic and resilient REC operations.
- c.
- Inclusive Governance and Community Engagement
Stronger emphasis should be placed on participatory governance structures that actively involve citizens, municipalities, SMEs, and marginalized groups. Transparent decision-making and equitable benefit-sharing models are critical to building trust and long-term community commitment.
- d.
- Hybrid Energy Models and Storage Optimization
Expanding RECs beyond solar PV to incorporate hybrid systems such as combinations of wind, biogas, and hydro with advanced energy storage will improve energy reliability and resilience, especially in off-grid or rural contexts.
- e.
- Cross-border and Inter-Community Collaboration
Future research and practice should explore regional networks and cooperative REC models, where multiple communities across borders share generation assets, storage facilities, and digital platforms, promoting energy solidarity and economies of scale.
- f.
- Replication in Developing and Vulnerable Regions
Lessons learned from successful European and global case studies should be adapted and applied to developing countries, particularly in rural, disaster-prone, or energy-insecure areas. Technical assistance, capacity-building, and North–South cooperation will be essential in this regard.
- g.
- Monitoring, Evaluation, and Data Transparency
Establishing standardized metrics for performance evaluation and encouraging data transparency will help to monitor progress, foster accountability, and facilitate evidence-based policymaking.
Finally, the overall analysis of the studied literature puts into evidence three main items that the success of REC implementation depends on
1—The fundamental role of user involvement, the social acceptance of RECs, their structure, and their working tools;
2—Overcoming the bureaucratic barriers, so tools that can achieve this must be supplied to REC members, and support from specially trained staff must be provided.
3—Financial support to constitute RECs or to build structures (e.g., PV fields, devices, plants, etc.) must be assured through proper tools.
9. Conclusions
RECs represent a cornerstone of the global shift toward decentralized, inclusive, and environmentally responsible energy systems. This review highlights the growing relevance of RECs in both European and global contexts, with particular attention to the evolving regulatory frameworks, e.g., the most notable European Union’s RED II directive, that have formalized and supported their development. The case of Italy, along with diverse international examples, demonstrates how RECs can adapt to local socio-economic, technical, and political conditions while meaningfully contributing to energy autonomy and climate objectives. Despite promising progress, challenges remain in harmonizing regulatory structures, ensuring fair market access, optimizing energy management, and fostering social acceptance. Addressing these issues through robust policy support, technological innovation, and active citizen engagement will be essential to fully realize the potential of RECs. As the energy landscape is continuously evolving, RECs offer a scalable and replicable model for accelerating the transition to a low-carbon future, empowering communities to play a central role in energy governance and sustainability.
Author Contributions
Conceptualization, S.C., P.C., D.A., and A.U.R.; methodology, S.C., P.C., D.A., and A.U.R.; writing—original draft preparation, P.C., D.A., and A.U.R.; writing—review and editing, P.C., D.A., and A.U.R.; visualization, S.C. and P.C.; supervision, S.C.; project administration, S.C., P.C., D.A., and A.U.R. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Data Availability Statement
No data are used.
Conflicts of Interest
The authors declare no conflicts of interest.
Abbreviations
The abbreviations used in this manuscript are given below:
| AI | Artificial intelligence |
| BESS | Battery energy storage systems |
| CEP | Clean energy package |
| CESS | Container energy storage system |
| CHP | Combined heat and power |
| LCOE | Levelized cost of electricity |
| CSO | Civil Society Organization |
| DBS | DC bus signaling |
| DSM | Demand-side management |
| DSO | Distribution system operator |
| ECO | Energy community operator |
| EMSs | Energy management systems |
| ENEA | National Agency for New Technologies, Energy and Sustainable Development |
| ESCo | Energy service company |
| IoT | Internet of things |
| LECs | Local energy communities |
| LEC | Local energy community |
| LLCEIs | Local low-carbon energy initiatives |
| LPG | Liquified petroleum gas |
| MILP | Mixed-integer linear programming |
| ML | Machine learning |
| MOPSO | multi-objective particle swarm optimization |
| NbSs | Nature-based solutions |
| NPV | Net present value |
| P2P | Peer to peer |
| PED | positive energy district |
| PKI | performance key indicator |
| PV | Photovoltaic |
| REC | Renewable energy community |
| RED | Renewable energy directive |
| RESs | Renewable energy sources |
| SECAP | Sustainable Energy and Climate Action Plan |
| SG | Smart grid |
| SMEs | Small and medium-sized enterprises |
Appendix A
Table A1.
Existing works about RECs and SG in Europe and across the globe with the adopted technologies, work nature, and storage system. (biomass—BM; biogas—BG; photovoltaic—PV; 1—wind; 2—solar; S; hydro—H; battery—B*; heat pump—HP; thermal—TH).
Table A1.
Existing works about RECs and SG in Europe and across the globe with the adopted technologies, work nature, and storage system. (biomass—BM; biogas—BG; photovoltaic—PV; 1—wind; 2—solar; S; hydro—H; battery—B*; heat pump—HP; thermal—TH).
| Ref. | Year | Country | Technology | Org. Type | Work Nature | Storage (Y/N, Type) |
|---|---|---|---|---|---|---|
| [2] | 2018 | EU | -- | EU directive | Policy and regulation | N |
| [4] | 2018 | NL | 1, 2, and BG | Energy initiatives | LLCEI | N |
| [5] | 2017 | NL | 1, 2, and BG | Energy initiatives | LLCEI | N |
| [6] | 2019 | EU, AUS, and NZ | S, 2, and RES | Legal/regulatory bodies | laws in the EU, Australia, and New Zealand | N |
| [7] | 2019 | EU | -- | EC | Regulation laws | N |
| [8] | 2021 | EU | General RES | RECs | Legal and policy framework | N |
| [9] | 2020 | EU | RES | EC | Laws, practice, and recommendations | N |
| [10] | 2021 | EU | DC grids and 1 | REC | Modeling and simulation of a REC | Y, Li-ion |
| [11] | 2021 | EU | 1 and 2 | REC | Management | N |
| [12] | 2022 | EU | RESs | REC | Model | Y, B* |
| [13] | 2021 | EU | RES | Policy research | Policy advice and RED II implementation | N |
| [14] | 2022 | EU | 1 | REC, CSC, and CEC | Model | N |
| [15] | 2023 | EU | 1 | RECs | Model | N |
| [16] | 2023 | EU | 1 | REC and ECO | Model | Y, B*, and EV |
| [17] | 2023 | EU | 1 | REC | Management | N |
| [18] | 2023 | EU | -- | -- | Laws | N |
| [19] | 2024 | EU | 2, S, and BM | RESs | Management | Y, H2 |
| [20] | 2020 | EU | -- | CSC and RECs | Report | N |
| [21] | 2022 | EU | -- | CEC | Laws and rules | N |
| [22] | 2024 | EU | -- | RECs | Review | N |
| [23] | 2024 | EU | -- | RECs | Review/management | N |
| [24] | 2023 | EU | RESs and S 1 | Smart communities | Management | Y, EV |
| [25] | 2024 | RO | General | REC | Bibliometric analysis | N |
| [26] | 2029 | IT | 1 | REC | Model | N |
| [27] | 2020 | IT | 1 | SSC and REC | Simulation | N |
| [28] | 2021 | IT | 1, EV, and heat pump | EC | Scenario modeling | Y, B* EV |
| [29] | 2020 | IT | 1 and multi-source RES | REC | Game-theoretic modeling | Y, multiple |
| [30] | 2021 | IT | -- | Cooperative RECs | Impact and taxonomy | N |
| [31] | 2019 | IT | 1, BM, and H | RECs | Taxonomy and regulation | N |
| [32] | 2021 | IT | RES | RECs | Sociological analysis | N |
| [33] | 2023 | IT | SG | EC | Management | N |
| [34] | 2019 | IT | RES/DSM | RECs | Management simulation with user-centric | Y, assumed |
| [35] | 2022 | IT | 1 and EVs | Scenario analysis | Case study for island | N |
| [36] | 2022 | IT | 1 | REC/ComER project | Modeling, forecasting, control, and commercial | Y |
| [37] | 2022 | IT | 1 and BM | REC | Model | N |
| [38] | 2022 | IT | 1 and S | REC | Model | N |
| [39] | 2022 | IT | 1 | REC | Model | N |
| [40] | 2022 | IT | 1 | REC | Management | N |
| [41] | 2022 | IT | 1 | REC | Management | Y, not specified |
| [42] | 2022 | IT | Urban focus | REC | Urban planning for REC integration | N |
| [43] | 2023 | IT | 1 and HPs | 1 and HP | Sustainable district renovation; zero emission | N |
| [44] | 2023 | IT | BESS and REC | BESS and REC | Ancillary services via BESS | Y, B* (BESS) |
| [45] | 2023 | IT | PEDs | REC in PEDs | Governance, prototyping, and implementation | N |
| [46] | 2023 | IT | REC | REC | Trends in REC development; comparison | N |
| [47] | 2023 | IT | Smart B* | Management and REC | Technical–economic evaluation of BMS | Y, BMS |
| [48] | 2023 | IT | REC | REC | Policy and legislative analysis; bureaucratic | N |
| [49] | 2023 | IT | 1 and storage | REC | Roadmap for REC creation and monitoring | Y, B* |
| [50] | 2023 | IT | AI, IoT, SG | SG, REC | Energy optimization and cooperation | N |
| [51] | 2023 | IT | Energy transition | REC | Social analysis of REC integration | N |
| [52] | 2023 | IT | DSM | REC | MILP-based DSM in RECs | N |
| [53] | 2023 | IT | 1, HPs, and electric and TH storage | Simulation tool and REC | RECoupled: simulation tool coupling electric and TH energy | Y, Electric and TH |
| [54] | 2023 | IT | REC planning | Urban planning | Model to detect low-income areas to plan RECs against poverty | N |
| [55] | 2023 | IT | PED | Policy | Policies and practices for RECs | N |
| [56] | 2023 | IT | RECs | Public sector | Municipality of Assisi: challenges and opportunities | N |
| [57] | 2023 | IT | -- | REC | Policy/Academic | N |
| [58] | 2023 | IT | Smart villages | RECs and rural REC | Green–digital transition guidelines | N |
| [59] | 2023 | IT | Architecture | RECs | Socioecological infrastructure | N |
| [60] | 2023 | IT | 1 panels | Municipal RECs | Economic/policy | N |
| [61] | 2023 | IT | -- | REC design tools | Optimization | N |
| [62] | 2024 | IT | -- | REC | Awareness of REC enhancement | N |
| [63] | 2024 | IT | H2-based MGs | Techno-economic | Modeling and optimization using | Y, H2 storage |
| [64] | 2025 | IT | 1 in RECs | Economic policy | Economic analysis of 1 system | N |
| [65] | 2024 | IT | H2-blended gas | Environmental | GHG emissions from H2-blended natural gas | N |
| [66] | 2024 | IT | -- | RECs in sea ports | Energy management | Y |
| [67] | 2024 | IT | 1 sizing | REC business | Case study | N |
| [68] | 2024 | IT | General REC | REC | Conceptual modeling | N |
| [69] | 2024 | IT | Geothermal | REC | Site suitability | N |
| [70] | 2024 | IT | 1 and HP | REC | Scenario simulation | N |
| [71] | 2024 | IT | Mixed (RES) | REC | Energy and economic | N |
| [72] | 2025 | IT | B* sizing | REC | Storage integration | Y, BESS |
| [73] | 2024 | IT | General REC | REC | Tool development | N |
| [74] | 2025 | IT | Battery | REC | Self-sufficiency model | Y, BESS |
| [75] | 2025 | IT | Mixed (DSM/1) | REC | Load shifting simulation | N |
| [76] | 2025 | IT | 1 industrial | REC | 1 sizing and clustering | N |
| [77] | 2025 | IT | 1 | REC | Policy and governance | N |
| [78] | 2025 | IT | General | REC | Social acceptance and awareness | N |
| [79] | 2024 | IT | 1 | REC | Load profiling and management | N |
| [80] | 2024 | IT | 1 rooftop | REC | Orientation impact | N |
| [81] | 2025 | IT | 1 | REC | Stochastic simulation | N |
| [82] | 2025 | IT | 1 | ENEA RECs/SECs | Structured framework | Y, Implied |
| [83] | 2023 | DE | Mixed (1/grid) | REC | Forecast uncertainty | N |
| [84] | 2023 | DE | 1/grid | REC | Tariff design effects and case study | N |
| [85] | 2024 | DE | 1 | Prosumer | Residential benefits | N |
| [86] | 2025 | DE | 1 and BESS | REC | Landlord–tenant supply | Y, BESS |
| [87] | 2022 | IT and DE | 1 and community energy | REC | Comparative policy/governance study | N |
| [88] | 2023 | PT | Mixed (1, EV, and grid) | REC/ecosystem | Case study analysis | Mixed (some) |
| [89] | 2023 | PT | 1, B*, and EV | REC | Modeling configurations | Y, Battery |
| [90] | 2023 | PT | 1 | REC | Sizing and classification | N |
| [91] | 2023 | PT | General | CREC | Governance simulation | N |
| [92] | 2023 | PT | 1 and storage | REC | Energy flow optimization | Y, Battery |
| [93] | 2023 | PT | Regulatory | REC | Energy sharing policy | N |
| [94] | 2023 | PT | 1 and storage | REC | Optimization MOPSO | Y, Battery |
| [95] | 2025 | PT | HEMS and optimization | REC | Strategy assessment | N |
| [96] | 2022 | PT | DERs and flexible loads | REC | Load scheduling | N |
| [97] | 2024 | PT | ML and electricity forecast | Cooperative | Demand forecasting | N |
| [98] | 2019 | NL | RES | Local initiatives | Empirical and governance analysis | N |
| [99] | 2025 | NL | DHS and AI-modeling | DHS (not REC) | TH modeling | Y, TH |
| [100] | 2019 | UK and NL | RES | Socio-legal and RED II | Regulations | N |
| [101] | 2023 | LV, NO, PT, and ES | RES | REC | Stakeholder motivations and policy alignment | N |
| [102] | 2024 | PL | Net-metering and 1 | Cooperative | Economic and policy analysis | N |
| [103] | 2025 | PL | BG, sewage, GSHP, 1, and TH | DHS and local | Techno-economic comparison | Y, TH |
| [104] | 2023 | CH | 1 and community S | Community S | Policy modeling | N |
| [105] | 2023 | DE, RO, ES, and NO | RESs procurement | Companies | SME executives’ preferences for local energy | N |
| [106] | 2022 | CZ | Regional CER case studies and 1 | Case studies/policy | village-based CERs (BM, S, and 1) | Y, some cases |
| [107] | 2023 | ES | 1 and optimization | REC | Operational modeling | N |
| [108] | 2023 | ES | TOPSIS | REC | Management and ranking | N |
| [109] | 2021 | ES | LECs and tariff economics | LEC | Policy and economic modeling | N |
| [110] | 2025 | ES | 2, H2 backup, and off-grid | Isolated | System design and modeling | Y, H |
| [111] | 2023 | ES | REC ecosystem and business models | REC | Business and model analysis | N |
| [112] | 2024 | ES | 1, 2, and storage | REC | REC design optimization using ML, and LCA | Y, not defined |
| [113] | 2022 | BE | RES, storage, and RES | REC | Economic efficiency, model, and management | Y, storage included |
| [114] | 2023 | BE | 1 system | REC | Technical grid impacts and model | N |
| [115] | 2023 | BE | Controllable assets | REC | Optimal control and management | N |
| [116] | 2023 | FR | Storage in RECs | REC | Configuration selection and model | Y, storage |
| [117] | 2021 | GR | Socio- economic analysis | CREE | Conceptual/theoretical framework/management | N |
| [118] | 2025 | GR | energy transition | REC/SG | Case study and policy and risk analysis | N |
| [119] | 2022 | IE | 2 energy for RECs | Resource assessment | Assesses 2 energy for RECs | No |
| [120] | 2020 | AT | Blockchain and RES | Tech R&D | Tech design and testing | Y, type not detailed |
| [121] | 2021 | AT | 1 + B* | Academic/research | Model | Y, B* |
| [122] | 2022 | AT | Legal RECs | Legal/policy | Real case | N |
| [123] | 2022 | MT | 1 + B* | Case study | optimization; peak shaving | Y, 10–57 kWh B* |
| [124] | 2023 | IS | 1, 2, S, TH, and H2 | Applied case study | Arctic REC storage: batteries | Y, batteries + TH + H |
| [125] | 2025 | HR | 1 + BESS | Modeling RECs | Sizing RECs | Y, BESS |
| [126] | 2020 | UA | S collector | Smart building | Simulation and building-integrated S and TH systems | Y, TH mass (wall-integrated) |
| [127] | 2024 | UA | 1, mini H, 2, and BG | REC | Modeling, autonomous RECs | N |
| [128] | 2024 | IT, DE, DK, and UK | 2 turbines | REC | State of the art, cooperatives, and energy poverty | N |
| [129] | 2024 | PT and BR | Consumption forecasting | REC | Machine learning-based forecast and management | N |
| [130] | 2021 | GE and NL | General RES | Community-led | Sociological analysis | N |
| [131] | 2021 | DE and NL | REC | Comparative study/policy analysis | Comparison of CER development | N |
| [132] | 2023 | NL and DE | Multi-functional energy gardens | REC | Transnational transfer of best practices | N |
| [133] | 2023 | ES, CH, BE, and NL | Sector-coupled, renewable energy | REC | Clean energy transition scenarios and modeling | N |
| [134] | 2023 | 11 Baltic countries | RESs and electricity | REC | Real case, community empowerment, and renewable transition | N |
| [135] | 2023 | — | 2 an S energy | REC | Stochastic multi-objective model for energy efficiency and planning | N |
| [136] | 2024 | USA | Renewable energy MG | REC | Optimization of MG operations | N |
| [137] | 2022 | USA | S, 2, and H2 storage | REC | MG for 10,000 homes and H2 storage key to CO2 reduction | Y, H2 storage |
| [138] | 2025 | KR | 1 to H2 | Real case | Real Case | Y, Surplus to H2 |
| [139] | 2023 | CA | 1, 2, BM, and hydroelectric | REC | Review of RECs | N |
| [140] | 2023 | CA | RESs | REC | Review of adoption in remote communities | N |
| [141] | 2024 | CA | RESs | REC | Analysis of energy transition and economic welfare for indigenous communities | N |
| [142] | 2024 | CA/KR | 1 and local/community storage | REC | Model of 6 residential RECs and trading | Y, community/local |
| [143] | 2024 | CG/AU/CA | 1, 2, BM, and H | REC | Multi-country case studies of off-grid RECs | Y, batteries |
| [144] | 2023 | NA/WE | CRE and nature-based solutions | Review | Systematic review on energy justice | N |
| [145] | 2023 | AF | Mixed RESs | REC | Real case of RECs in five African countries | N |
| [146] | 2024 | ZA | Legal and governance framework | Review | Review on poverty reduction via RE | N |
| [147] | 2025 | ZA | 1, 2, and BM | REC | Policy study on small-scale RE in agriculture | N |
| [148] | 2017 | ZA | Socioeconomic | Management | Policy analysis for RE migration | N |
| [149] | 2024 | LS | Mini-H and 1 | REC | Real case study of community participation | N |
| [150] | 2024 | NA | 1, 2, BM, and geothermal | Management | Challenges and prospects of community RE | N |
| [151] | 2023 | UG | RE project engagement | Management | Community-based RE project management | N |
| [152] | 2024 | IN/NG | Hybrid 1–2 | Model | Techno-economic optimization | Y, Hybrid |
| [153] | 2024 | KE | 2 large and 1 small | REC | Community trade-offs in RE size and awareness | N |
| [154] | 2024 | IN | 1 | REC | Energy poverty, decarbonization, and case studies | N |
| [155,156,157,158] | 2021-23 | PK | Hybrid RES, diesel, 1, 2, and S | Village and smart homes | Real case, scenarios, decarbonization, and SG | B* backup |
| [159] | 2022 | IR | 1 and 2 | Model | Modeling | N |
| [160] | 2024 | CN | 2 and energy hub | Model | Modeling | Y, Energy hubs |
| [161] | 2023 | KR and PK | Hybrid 1 and BG | Community | Management | Y, BG, hybrid |
| [162] | 2023 | KR | 1, geothermal, and HP | Community | Real/model | Y |
| [163] | 2024 | KR | High RES and DSM | Model | Modeling | Y, Storage critical |
| [164] | 2023 | AUS | VPP and RES | REC | Case study on VPP reducing CO2 and transition | Y, storage evaluated |
| [165] | 2023 | AUS | Hydroelectric | REC | RECs in community disaster risk reduction | N |
| [166] | 2025 | Fiji Islands | 1 rooftop | REC | Case studies on RECs fostering resilience | N |
| [167] | 2010 | NZ | Legislation | Govt. law | Legislation “Electricity Industry Act 2010” | N |
| [168] | 2023 | EU | 1 and 2 | REC | Model | Y, Re-pump |
| [169] | 2024 | UA | BG | BG plant in building | Bioreactors/farms | N |
| [170] | 2024 | — | RES distributed | Review | 123 articles on RECs and RESs | N |
| [172] | 2023 | EU | REC deployment | REC/SG | Survey, classification, and policy review of REC | N |
| [173] | 2021 | TR/DE | REC economic models | REC/SG | Investment and cost-sharing strategies in energy communities | Y, assume storage |
Appendix B
Our preferred reporting items for systematic reviews and meta-analyses (PRISMA)-based schematic diagram in Figure A1 illustrates the whole workflow of our literature search, screening, and selection process. We targeted the article title, abstract, and keywords fields. The search strings we used to capture studies related to the policy, modeling, implementation, technological, and policy aspects of RECs and their role in the energy transition are also shown. Literature retrieval was conducted primarily via leading academic databases and Scopus (MDPI, IEEE Xplore, ScienceDirect, and SpringerLink) using the following refined keywords:
(“Renewable Energy Communities” OR “Community Energy” AND “Energy Transition” AND “Distributed Energy” OR “Distributed Generation” OR “Decentralized Energy Systems” OR “Smart Energy Solutions” OR “Energy Management” AND “Sustainability” OR “Energy Innovation” AND “Renewable Energy Directive” OR “RED II” AND “RED III”) AND (“Economic Impact” OR “Feasibility” OR “Benefits” AND “Barriers” OR “Community Participation” AND “Optimization” OR “Policy Impact” AND “Regulatory Framework”)
Figure A1.
Our preferred reporting items for systematic reviews and meta-analyses (PRISMA)-based schematic diagram illustrates the whole workflow of our literature search and framework.
Figure A1.
Our preferred reporting items for systematic reviews and meta-analyses (PRISMA)-based schematic diagram illustrates the whole workflow of our literature search and framework.
Appendix C
In 2023, renewable energy made up 24.5% of the total energy consumed in the EU, a nice increase from 23.0% in 2022. Additionally, the portion of energy from renewable sources used in transportation in the EU hit 10.8% in 2023, up from 9.6% of the previous year. The crucial issue regarding the economic impact of RECs (Figure A2 and Figure A3) provides complementary insights. Figure A2 illustrates the share of renewable energy in final energy consumption across European countries in 2023, alongside their 2030 targets. Several countries, such as Sweden, Finland, and Denmark, have already surpassed or are on track to meet their targets, indicating strong national momentum in renewable deployment. While this reflects national policy ambition and technological readiness, Figure A3 complements it by capturing the grassroots deployment of RECs, measured through the number of communities, the average membership size, and the number of citizens benefiting directly from community-generated electricity. Countries such as Germany (847 RECs), the Netherlands (676), and Italy (423) stand out not only for their REC volume but also for the scale of citizen engagement and household-level energy consumption. For instance, Italy’s 88,272 households consuming REC-produced electricity represent a tangible translation of policy into localized economic activity, energy democratization, and social innovation. These patterns suggest that RECs, when institutionally supported, catalyze inclusive participation in the energy transition, stimulate regional investment, and contribute to long-term economic resilience through community ownership models, cooperative governance, and reinvestment of profits in local infrastructures. Thus, RECs are not merely energy producers; they are emerging as microeconomic hubs that align with national decarbonization goals while anchoring economic empowerment at the community level. Figure A2 shows the share of energy from the renewable energy source in (%) and the target of each EU country by 2030 [171]. Figure A3 illustrates the growth and deployment of REC in EU countries, with Italy highlighted in [172,173].
Figure A2.
Share of renewable energy in final energy consumption across European countries in 2023, as well as their 2030 targets.
Figure A2.
Share of renewable energy in final energy consumption across European countries in 2023, as well as their 2030 targets.
Figure A3.
Growth and deployment of RECs in EU countries.
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Figure 1.
Implementation of a REC with open and voluntary participation, steps, and core advantages.
Figure 1.
Implementation of a REC with open and voluntary participation, steps, and core advantages.
Figure 2.
REC role, activities, and benefits.
Table 1.
Summary of renewable energy community studies by country.
| Distribution of Studies Per Country | |||||||
|---|---|---|---|---|---|---|---|
| Country | No. of Studies | Country | No. of Studies | Country | Studies | Country | Studies |
| Australia | 3 [164,165,166] | South Africa | 4 [145,146,148,149] | Malta | 1 [123] | Brazil | 1 [129] |
| Poland | 2 [102,103] | Uganda | 1 [150] | North Africa | 1 [150] | Pakistan | 5 [155,161] |
| Switzerland | 1 [104] | EU (General) | 19 [7,8,9,10,11,12,14,15,16,17,18,19,20,21,22,23,24,66,168] | Norway | 2 [101,105] | Romania | 1 [25] |
| Canada | 3 [139,140,141] | South Korea | 4 [138,161,162,163] | Baltic 11 | 1 [134] | Iceland | 1 [124] |
| Czech Republic | 1 [109] | Spain | 6 [107,108,109,110,111,112] | The Netherlands | 2 [98,99] | Italy | 52 [26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81] |
| New Zealand | 1 [6] | Denmark | 1 [20] | United Kingdom | 5 [20,100,128,129,133] | Belgium | 2 [113,114] |
| France | 1 [116] | Greece | 3 [54,116,118] | Iran | 1 [159] | Ireland | 1 [119] |
| Germany | 4 [82,83,84,85,86] | USA | 3 [134,135,136] | Latvia | 1 [101] | India | 1 [154] |
| Nigeria | 1 [152] | Portugal | 10 [88,89,90,91,92,93,94,95,96,97] | Austria | 3 [120,121,122] | EU (Mix) | 19 [7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24] |
Table 2.
Summary of research work in RECs by continent, technology, study type, and comparison with the present work.
Table 2.
Summary of research work in RECs by continent, technology, study type, and comparison with the present work.
| a. Distribution by Continent | b. Technologies Covered | c. Review Articles Identified | |||
|---|---|---|---|---|---|
| Continent | No. of Studies | Technology | No. of Studies | Type | Count |
| Europe | 134 | Biomass | 4 | Review Papers | Total = 9; [22,23,24,25,31,139,140,144] |
| Asia | 11 | PV | 29 | Our work: This review examines the evolution and implementation of RECs, focusing on EU regulations (RED II and III), the technologies used, governance models, and socioeconomic strategies. Case studies from Europe, Asia, and Africa highlight the main roles, activities, and benefits, as well as approaches and challenges. | |
| America | 10 | Wind | 7 | ||
| Africa | 8 | Geothermal | 2 | ||
| Australia | 6 | Hydroelectric/Mini-Hydro | 4 | ||
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Corasaniti, S.; Coppa, P.; Atzori, D.; Rehman, A.U. Renewable Energy Communities (RECs): European and Worldwide Distribution, Different Technologies, Management, and Modeling. Energies 2025, 18, 3961. https://doi.org/10.3390/en18153961
AMA Style
Corasaniti S, Coppa P, Atzori D, Rehman AU. Renewable Energy Communities (RECs): European and Worldwide Distribution, Different Technologies, Management, and Modeling. Energies. 2025; 18(15):3961. https://doi.org/10.3390/en18153961
Chicago/Turabian StyleCorasaniti, Sandra, Paolo Coppa, Dario Atzori, and Ateeq Ur Rehman. 2025. "Renewable Energy Communities (RECs): European and Worldwide Distribution, Different Technologies, Management, and Modeling" Energies 18, no. 15: 3961. https://doi.org/10.3390/en18153961
APA StyleCorasaniti, S., Coppa, P., Atzori, D., & Rehman, A. U. (2025). Renewable Energy Communities (RECs): European and Worldwide Distribution, Different Technologies, Management, and Modeling. Energies, 18(15), 3961. https://doi.org/10.3390/en18153961
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