Technological Readiness and Implementation Pathways for Electrifying Greek Coastal Ferry Operations: Insights from Norway’s Zero-Emission Ferry Transition

Abstract

The decarbonization of short sea shipping is emerging as a critical priority for Mediterranean countries. This paper presents key findings from the ELECTRA-GR project, funded by the EEA Financial Mechanism (MIS 5202231), which aimed to evaluate the feasibility, technical readiness, and legislative requirements for the electrification of coastal ferry services in Greece. The study focused on two pilot routes—Salamis–Perama and Chios–Oinousses— representative of the high-frequency, short-distance ferry operations characteristic of the Greek archipelago. A comprehensive assessment was conducted combining technical fleet profiling, stakeholder consultations, legislative analysis, cost–benefit evaluations, and international benchmarking with Norway. For the base scenario of the high-traffic Salamis–Perama route, full electrification yields an annual reduction of approximately 900 tons of CO₂ compared to diesel operation and achieves a Net Present Value (NPV) of €1.6 million over a 15-year period. In contrast, the Chios–Oinousses route, characterized by lower traffic volume, achieves a reduction of 85 tons of CO₂ annually through hybrid conversion, but results in an NPV of €−1.69 million, underscoring the need for financial support mechanisms or targeted subsidies to ensure economic feasibility. The results indicate that electrification of short ferry routes in Greece is technically feasible and environmentally advantageous but faces significant challenges, including inadequate port infrastructure, regulatory gaps, and limited industrial readiness. The study proposes a structured roadmap toward electrification, emphasizing the modernization of shipyards, tailored policy instruments, and public–private cooperation. The findings contribute to the formulation of a scalable strategy for clean maritime transport in peripheral and island regions of Greece.

1. Introduction

The decarbonization of maritime transport is a central objective of European and global climate policy. European policy frameworks have promoted modal shifts from road to sea and enhanced the role of Short Sea Shipping (SSS) through various environmental, logistical, and intermodal initiatives [1]. SSS and, in particular, the ferry services connecting coastal and island communities, represent a segment with significant potential for emissions reduction through electrification and hybrid propulsion systems [2,3,4,5]. In the context of the Mediterranean and especially in Greece—with its extensive coastline, over 100 inhabited islands, and 278 ferry routes—coastal shipping constitutes a critical infrastructure for regional accessibility, social inclusion, and economic development.

However, the Greek coastal fleet is aging, fragmented, and reliant on conventional marine diesel engines, resulting in elevated emissions of greenhouse gases (GHGs), sulfur oxides (SOx), and particulates. The average age of passenger vessels exceeds 26 years, with more than 70% of the fleet falling within the 11–40-year range. Furthermore, while Greece has a strong maritime sector, including shipbuilding capacity and marine equipment supply chains, there are limited initiatives for clean propulsion retrofits or new builds. Port infrastructure also lacks the necessary cold ironing and high-voltage charging facilities, creating a bottleneck for zero-emission shipping deployment.

In this context, the ELECTRA-GR project, supported by the EEA Financial Mechanism (MIS 5202231), was undertaken to assess the technological readiness, economic feasibility, and regulatory requirements for electrifying Greek coastal ferry operations. The project adopts a multi-layered methodology, including technical profiling of selected ferry fleets, infrastructure and shipyard capacity assessment, cost–benefit and environmental impact analysis, and a comparative study of Norwegian best practices—Norway being a global pioneer in the field of electric ferries [6].

Two short-distance routes were selected as pilot cases: the Salamis–Perama line, which is the busiest ferry route in Greece in terms of annual traffic volume, and the Chios–Oinousses route, a representative public service obligation (PSO) line with strategic socio-economic relevance. Both routes were examined in detail regarding fleet structure, energy and propulsion characteristics, retrofitting potential, regulatory framework, and stakeholder perceptions.

This paper presents a synthesis of the project’s findings, with the aim of proposing an actionable roadmap for electrifying Greek ferry services. The remainder of this article is structured as follows: Section 2 outlines the methodology and data sources used in the analysis. Section 3 presents the results of the two case studies, including techno-economic performance, environmental impacts, and sensitivity assessments. Section 4 discusses institutional, regulatory, and infrastructural enablers and barriers. Finally, Section 5 concludes with key findings and policy implications.

2. Materials and Methods

2.1. Background and Literature Review

Maritime transport is a significant contributor to global greenhouse gas (GHG) emissions, accounting for nearly 3% of total anthropogenic emissions [7]. Within the maritime sector, short sea shipping (SSS) presents both a challenge and an opportunity for decarbonization. Ferry operations, particularly on short, high-frequency routes, generate substantial local air pollution and offer a favorable operational profile for electrification due to their predictability, route regularity, and limited sailing distances [8].

In Greece, coastal shipping is a lifeline for more than 100 inhabited islands. With over 270 routes and approximately 19 million passengers served annually, the sector plays a pivotal role in economic cohesion and regional development. However, the Greek ferry fleet is aging, with an average vessel age of over 26 years and a heavy reliance on diesel propulsion. Emissions from these vessels impact not only the climate but also local air quality, especially in port cities such as Piraeus and Heraklion.

Reference [9] found that partial electrification of Greek coastal shipping is feasible, with potential reductions in GHG emissions from electric ferries. Despite the technical feasibility of electrification, the Greek coastal shipping sector remains under-electrified, with limited port infrastructure for shore-side charging, few pilot deployments, and a regulatory environment that lacks clear incentives or standards for zero-emission vessel integration.

Norway has emerged as the global leader in ferry electrification, driven by coordinated public policy, green procurement mandates, and robust investment in port infrastructure. Reference [10] highlights Norway’s ferry electrification suggesting a set of success criteria for accelerated transitions. As of 2022, over 70 battery-electric or hybrid-electric ferries operate in Norwegian waters [11]. This transition was supported by instruments such as the Enova grant scheme, national tendering requirements for low-emission vessels, and the development of classification standards for battery systems.

Norway’s experience highlights several critical enablers that have contributed to the successful electrification of its ferry sector. These include strong government commitment expressed through comprehensive long-term strategies, such as Norway’s Maritime Strategy, as well as the establishment of funding mechanisms designed to de-risk early adoption by covering capital or operational costs.

Equally important are the development and enforcement of standardized safety and certification protocols, which ensure regulatory clarity and operational reliability. Another defining feature of the Norwegian approach is the close collaboration among shipowners, port authorities, shipyards, and technology providers, fostering a unified ecosystem for innovation and implementation [6]. These lessons are highly relevant to the Greek context, especially for short, high-frequency routes such as Salamis–Perama and for public service obligation (PSO) lines like Chios–Oinousses.

Two main propulsion technologies are currently employed in maritime electrification. Battery-electric vessels (BEVs) rely exclusively on energy stored in onboard batteries to power both propulsion and auxiliary systems. These vessels are particularly well suited for short routes, typically under 30 min in duration, and benefit from frequent port calls that allow for regular recharging. In contrast, hybrid-electric vessels (HEVs) combine battery systems with conventional internal combustion engines or dual-fuel generators. This configuration enables zero-emission operations while in port and allows partial electric propulsion during sailing, providing operational flexibility for longer or less predictable routes [5].

Marine battery systems must meet stringent requirements for energy density, operational safety, and lifecycle efficiency. Among the most commonly used battery chemistries are Nickel Manganese Cobalt (NMC), which offers high energy capacity and is widely applied in medium-to-large ferries, and Lithium Iron Phosphate (LIP), known for its enhanced thermal stability and growing use in newer maritime applications.

Battery capacities generally range from 500 kWh to over 6 MWh, depending on the vessel size and the specific route requirements.

For example, vessels operating on the Salamis–Perama route could be retrofitted with battery systems ranging from 1 to 1.5 MWh, allowing for multiple crossings between charges.

Crucial to the performance and safety of these systems are Battery Management Systems (BMS), which monitor charging cycles, regulate thermal conditions, and ensure safe operation under varying maritime conditions [6].

Effective electrification of maritime operations requires robust shore-side energy infrastructure, which is currently underdeveloped in Greece.

Charging technologies typically include plug-in systems utilizing high-voltage cables, automatic connectors that engage upon docking, and pantograph systems—similar to those employed in tram and bus networks. The speed of charging depends on the capacity of the infrastructure; for instance, a 2 MW charger can deliver a full charge to a 1 MWh battery in approximately 30 min.

While opportunity charging during short port calls has become standard practice in Scandinavian ferry operations, such systems are still absent from Greek ports [12].

To ensure the sustainability and resilience of future port electrification, grid upgrades, peak load management strategies, and the integration of local renewable energy sources—such as solar-assisted port microgrids—are strongly recommended.

Battery systems introduce unique fire, explosion, and thermal hazards that necessitate stringent safety measures throughout both design and operation. International regulations provide the foundational framework for these protocols. Specifically, ref. [13] Chapters II-1 and II-2 govern electrical installations and fire protection on ships, while refs. [14,15] specify requirements for rechargeable battery design and performance. Shore-power connections must comply with the [16,17,18], which cover high-voltage onshore power supply systems.

Classification societies have supplemented these regulations with detailed guidance tailored to maritime battery installations. Det Norske Veritas has developed dedicated rules and safety guidelines for battery systems on ships, specifying technical requirements and safety assessment procedures.. Similarly, Lloyd’s Register provides approval processes for battery installations, focusing on hazard identification and mitigation strategies.

To achieve class certification, all-electric vessels must secure both a Battery System Safety Description from the battery manufacturer and a Safety Assessment conducted by the operator or system integrator, ensuring that the installed battery system meets the rigorous safety criteria established by these regulations and societies [19].

The electrification of vessels involves far more than simply replacing internal combustion engines with batteries. It requires addressing a series of complex integration challenges, including the added weight and optimal placement of battery systems, the redesign and conversion of onboard electrical systems, the installation of appropriate fire suppression and ventilation solutions, and the incorporation of redundancy in both propulsion and auxiliary systems to ensure operational safety and reliability. Regarding safety, modern fire suppression systems specifically designed for maritime battery compartments, such as aerosol-based, gas-based, or water mist systems, are commercially available and compliant with class society and IMO requirements, enabling safe integration of large-scale battery storage on board.

A practical example of such integration is the Sikania II Hybrid, launched by Kanellos Shipyards in Perama. This vessel demonstrates the technical feasibility of electrification within Greek shipyards. It operates with a diesel-electric propulsion system, incorporates 1 MWh of Nickel Manganese Cobalt (NMC) batteries, and is equipped with solar panels that generate 25 kW of power for auxiliary systems [20].

Several Greek shipyards—including Elefsis, Neorion, and Chalkis—have the drydock capacity, skilled labor force, and fundamental technical expertise required for undertaking electric retrofit projects. Nonetheless, notable limitations persist, particularly in advanced system integration capabilities and the domestic availability of certified components essential for fully compliant electrification projects.

At the European Union level, a range of policy instruments has been introduced to support the decarbonization of the maritime sector. The European Green Deal sets the overarching goal of achieving net-zero greenhouse gas emissions by 2050, establishing the foundation for sectoral initiatives [10]. One of the key legislative measures is the FuelEU Maritime Regulation (EU 2023/1805), which imposes progressively stricter greenhouse gas intensity targets for marine fuels. In addition, the inclusion of maritime transport in the EU Emissions Trading System (EU ETS) introduces a carbon pricing mechanism for shipping operations, thereby creating financial incentives for emissions reductions [1]. Complementing these regulatory efforts are EU-level funding mechanisms such as the Connecting Europe Facility (CEF) for Transport, the Innovation Fund, and Horizon Europe, all of which provide support for investments in green port infrastructure and low-emission vessel technologies [21].

Despite these developments at the EU level, Greece currently lacks a coherent national strategy specifically targeting the deployment of electric vessels. Several regulatory and institutional challenges remain unaddressed. These include the absence of mandatory electrification targets, the lack of established classification protocols for battery-powered vessels sailing under the Greek flag, and limited electrification infrastructure at Greek ports, with only a few exceptions such as the cruise terminals in Heraklion and Piraeus.

Electrification of vessels covering small distances. Furthermore, there are insufficient financial incentives and a lack of public procurement programs that explicitly prioritize zero-emission vessels. These gaps highlight the urgent need for legislative reforms, targeted funding for pilot projects, and coordinated capacity-building initiatives, drawing on international best practices such as those implemented successfully in Norway.

2.2. Methodology

The methodological approach of the ELECTRA-GR project was structured to assess the feasibility and implementation pathways for electrifying Greek coastal ferry operations across four main dimensions: (i) technical profiling of ferry fleets and infrastructure; (ii) assessment of domestic shipbuilding capacity and technological readiness; (iii) legislative and stakeholder analysis; and (iv) cost–benefit and environmental impact evaluation. A comparative lens was applied throughout, drawing on the experience of Norway’s zero-emission ferry transition as a benchmark.

The selection of the two pilot ferry routes was based on their operational characteristics, strategic importance, and potential for replication in other parts of the Greek coastal network. The first route, Salamis–Perama, is a short-distance connection of approximately 1 nautical mile between the island of Salamis and the port of Perama, near Piraeus. It represents the busiest ferry route in Greece in terms of passenger and vehicle traffic, with more than 7 million passengers and 3.7 million vehicles transported in 2023 [22]. Its high-frequency service and proximity to major urban centers make it a prime candidate for early adoption of electrification technologies.

The second route, Chios–Oinousses, spans approximately 10 nautical miles and connects the island of Chios with the smaller, remote island of Oinousses. This route operates under a public service obligation (PSO) framework and exemplifies the type of inter-island connection that serves socially critical but commercially less viable communities. It offers a representative case for assessing the feasibility of deploying small electric ferries on subsidized lines, particularly those with lower traffic volumes and limited economies of scale.

A comprehensive survey was conducted on the vessels operating on the selected routes. For each vessel, data were collected on length, beam, deadweight tonnage, propulsion system, fuel type, passenger and vehicle capacity, service speed, and year of construction. Data sources included classification society registries (DNV, Lloyd’s Register), national maritime authorities, shipowners, and maritime technical databases. Technical characteristics were cross-validated with site visits, interviews, and specifications provided by operators.

Simultaneously, port infrastructure was evaluated in terms of its readiness to accommodate electrified vessels. Parameters included berth layout, power grid access, cold ironing plans, and space availability for future charging installations. Greek port master plans were reviewed, and interviews with local port authorities were conducted.

Greek shipbuilding and marine equipment sectors were mapped based on literature review and semi-structured expert interviews. The analysis focused on large shipyards (Elefsis, Skaramangas, Neorion Syros) and clusters of small yards in Perama and Salamis. Metrics included drydock capacity, workforce skills, prior experience with hybrid/electric retrofits, availability of suppliers, and relationships with international technology providers (e.g., ABB, Siemens, Wärtsilä). Industry associations such as HEMEXPO were consulted for broader ecosystem insights.

The project undertook a dual assessment of the legislative environment and stakeholder perceptions. First, a legal gap analysis was conducted by reviewing Greek and EU regulations governing electric ship construction, certification, safety, and funding. The current national framework was contrasted with Norway’s legislative model for zero-emission vessels [6]. Key sources included SOLAS, EU directives (e.g., 2014/94/EU, Fit for 55), and national maritime laws.

Second, stakeholder engagement included structured interviews with 40 participants from public authorities, port organizations, shipowners, classification societies, shipyards, equipment suppliers, and academia. A targeted consultation workshop was also held (the input was collected from 14 participants selected through purposive sampling, representing public authorities, classification societies, academia, and ship operators), enabling qualitative feedback on technological barriers, market uncertainty, and regulatory gaps. Responses were analyzed thematically and triangulated with technical findings. While detailed methodological aspects are not the focus of this paper, the consultation process was carefully structured to ensure relevance, representativeness, and analytical value.

For each case study, a techno-economic model was developed comparing three vessel scenarios: conventional diesel propulsion, hybrid propulsion, and full-electric propulsion. Capital expenditure (CAPEX), operational expenditure (OPEX), fuel costs, maintenance costs, battery lifecycle, and infrastructure investment were incorporated. Fuel savings and emission reductions were estimated using standard maritime emission factors from IMO and EMSA guidelines [7,12]. In particular, the estimation of battery performance over the 15-year lifetime was based on a conservative linear degradation rate of 2% annually, reflecting a mid-range scenario from available Li-ion maritime battery studies [7,23]. Emission reductions were calculated using emission factors of 3.114 kg CO₂ per kg of marine diesel oil (MDO) and 0.5314 kg CO₂ per kWh of electricity [7,24].

A sensitivity analysis was performed to test the impact of key variables including battery cost, energy prices, carbon pricing (ETS inclusion), and grant support levels. In parallel, environmental benefits were assessed in terms of avoided GHGs and air pollutants (SOx, NOx, PM), particularly in populated port areas.

Economic outputs such as NPV and payback period were validated against vendor quotes, sensitivity-tested across ±20% CAPEX/OPEX ranges, and reviewed through expert feedback to ensure methodological consistency.

The economic modeling assumes a 15-year evaluation horizon, corresponding to the expected lifespan of coastal ferry vessels operating under PSO routes, and consistent with national fleet renewal programs and depreciation schedules. A discount rate of 4% is applied, reflecting the European Commission’s recommended rate for public investment evaluations in Greece and other cohesion countries [25].

It should be further noted that while the present analysis quantifies CO₂ emission reductions resulting from vessel electrification, it does not assess localized air quality impacts or the dispersion of specific pollutants in the surrounding port areas. Such environmental evaluations require specialized data, modeling tools, and methodologies, and are considered beyond the scope of this study. They may, however, constitute the focus of future dedicated research.

3. Results

This section presents the main findings of the ELECTRA-GR project concerning the technological, economic, and institutional feasibility of electrifying short-sea ferry operations in Greece. Drawing on case studies, technical modeling, and stakeholder engagement, the analysis provides a comprehensive evaluation of readiness factors, infrastructure needs, benefit streams, and policy challenges. The content is structured around two pilot routes—Salamis–Perama and Chios–Oinousses—which reflect differing operational profiles and electrification strategies.

The choice of those pilot cases was not based solely on traffic volume or route distance. The Salamis–Perama route, characterized by high-frequency operations and relatively short distances, allows efficient battery utilization and shore-side charging between sailings, thus favoring a full-electric newbuild approach. The large Ro-Ro ferries on this line offer sufficient space for battery installation without compromising cargo or passenger capacity. In contrast, the Chios–Oinousses route serves lower traffic volumes with fewer daily sailings, typically operated by smaller vessels with space and weight constraints, making it more appropriate for a hybrid-electric retrofit strategy focused on port emissions reduction and partial diesel substitution.

Each subsection presents specific dimensions of the feasibility analysis, including vessel design, grid and port infrastructure, capital and operational costs, and the projected benefits from reduced emissions and energy savings. These results provide a foundation for the recommendations and broader policy implications discussed in the following chapter.

The modeling approach is based on average daily operational profiles, using key input figures such as vessel power rating, number of daily round trips, and typical layover durations. These assumptions reflect standard service patterns rather than time-resolved energy simulations, aiming to provide a representative estimation of daily energy needs for comparative analysis.

3.1. Case Study—Salamis—Perama Route

The ferry connection between Salamis Island and Perama, a suburb of Piraeus, is the most heavily trafficked short-sea shipping route in Greece. The crossing spans approximately 1 nautical mile and operates continuously, with a frequency reaching up to 80 round trips per vessel per day during peak periods. The route facilitates the movement of commuters, private vehicles, and light commercial traffic, offering a critical mobility lifeline in the absence of a fixed link.

In 2023, the route transported more than 7.1 million passengers and 3.7 million vehicles, accounting for approximately 38% of all national coastal ferry vehicle traffic and over 20% of passenger movements [22]. These figures place the Salamis–Perama line among the busiest ferry corridors in the European Union, highlighting its strategic importance in terms of both mobility and environmental footprint.

The route is served by a fleet of approximately 40 double-ended Ro-Ro ferries, owned by a mix of private Greek operators including Tsokos Lines, Agios Fanourios Ferries, and others. The majority of vessels were built locally in Perama or Elefsis shipyards and are optimized for short, frequent crossings with fast embarkation and disembarkation procedures.

A typical vessel operating on the line has the following characteristics:

• Length overall (LOA): 90–100 m;
• Beam: 17–18 m;
• Deadweight tonnage (DWT): 800–1000 tons;
• Passenger capacity: 330–900;
• Vehicle capacity: 150–200;
• Main propulsion: Diesel engines (usually 2 × 750 kW);
• Service speed: 12–13 knots.

Vessels are typically manned by small crews and feature minimal hotel loads, making them operationally simple and relatively lightweight, which is advantageous for electrification.

The operational profile of the route—short distance, high frequency, and standardized vessel type—makes it a prime candidate for full battery-electric conversion.

Recent studies have demonstrated that ferry electrification is more feasible and cost-effective in short-distance, high-frequency routes with predictable power demand [3].

Modeling conducted during the ELECTRA-GR project shows that a 1–1.5 MWh lithium-ion battery system could meet the energy demands for multiple round trips, particularly when supported by opportunity charging infrastructure at one or both terminals.

Charging duration per cycle is estimated at 5–10 min using 1–2 MW shore power systems. This aligns with the brief layover time of vessels during loading and unloading. The implementation of pantograph or automatic plug-in systems would allow for rapid, safe, and repeatable charging without disrupting service frequency. This estimate assumes a charger efficiency of approximately 95%, consistent with modern DC fast-charging systems deployed in maritime settings. The assumed layover of at least 30 min between round trips aligns with current operational patterns observed on the route, enabling sufficient opportunity charging without altering vessel scheduling or turnaround practices.

The flat load profile, consistent vessel types, and predictable schedules further enhance the feasibility of electrification. Moreover, the limited hotel load and relatively low auxiliary energy consumption compared to cruise or overnight ferries reduce system complexity and battery size requirements.

The successful deployment of electric ferries depends heavily on the availability of adequate onshore infrastructure at port terminals, particularly for high-frequency routes where rapid turnaround is critical. Investments are needed in ship charging systems, grid connections, and energy management technologies. In this context, the concept of transforming ports into smart micro-grids—integrating renewable energy sources, battery storage, and intelligent control systems—has emerged as a promising model for future-ready ferry terminals [26].

However, despite the suitability of this model, several infrastructural and institutional barriers hinder implementation. At present, neither the Salamis nor the Perama terminal is equipped with cold ironing capabilities or high-capacity charging systems necessary for electric vessels. Local electricity substations in both areas may require substantial upgrades to meet the increased power demand, particularly if multiple vessels need to connect simultaneously. Moreover, the fragmented governance structure of port terminals poses challenges in coordinating investments, obtaining permits, and clarifying responsibilities related to the deployment of shore-side equipment.

Another key limitation is the absence of regulatory mandates or incentives to promote electrification. Unlike Norway, where policy tools and funding mechanisms have facilitated a rapid transition to electric coastal shipping, Greece currently lacks comparable instruments to support such initiatives. Nevertheless, the proximity of the Perama shipbuilding zone to the ferry terminal presents an opportunity for synergistic development. The zone’s existing industrial base, skilled workforce, and experience in constructing small vessels could be leveraged to support both newbuilding and retrofitting of electric ferries, provided that targeted capacity-building and training programs are introduced.

The full or partial electrification of the Salamis–Perama fleet presents a significant opportunity for both economic and environmental gains. A complete fleet conversion could lead to a reduction in CO₂ emissions by up to 80%, based on Greece’s current electricity generation mix, thereby contributing meaningfully to national decarbonization goals aligned with the EU Fit for 55 legislative package. In addition to greenhouse gas reductions, electrification would also lower emissions of nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM), offering direct improvements to local air quality in Perama—an area characterized by dense population and high industrial activity.

Moreover, the transition to electric propulsion would result in a noticeable decrease in noise levels, both onboard and at the port, thus improving passenger experience and benefiting residents in nearby communities. Despite the elevated capital costs associated with battery systems and port charging infrastructure, lifecycle cost modeling suggests that total operating expenses are lower over time, primarily due to savings in fuel and maintenance requirements [5].

A compelling demonstration of this potential is the Sikania II Hybrid Ferry, introduced in 2023 by Kanellos Shipyards specifically for service on the Salamis–Perama line. This vessel features a diesel-electric propulsion configuration combined with a 1 MWh battery system and solar panels that generate 25 kW to support auxiliary loads [20], highlighting the technical feasibility and cost-effectiveness of hybrid-electric solutions in the Greek ferry sector.

3.2. Case Study—Chios—Oinousses Route

The ferry connection between Chios and Oinousses serves as a remote and sparsely populated island cluster in the eastern Aegean Sea. The line is classified as a Public Service Obligation (PSO) route and subsidized by the Greek state due to its strategic importance for territorial cohesion, social connectivity, and maritime safety.

The route spans approximately 8.5 nautical miles, with an average one-way sailing time of 35–40 min depending on sea state. Services are typically operated 1–3 times daily, depending on seasonality, weather conditions, and demand, and are vital for commuting, education, healthcare access, and the transport of essential goods.

Despite the low volume of passengers and vehicles, the route is crucial for social equity and economic sustainability on Oinousses, which has a permanent population of fewer than 1000 residents but is home to significant maritime heritage and shipping capital.

The route is currently served by small multipurpose ferries or landing crafts, with limited passenger accommodation and freight capability. A representative vessel used in recent years features:

• Length: 45–55 m;
• Passenger capacity: ~100;
• Vehicle capacity: ~8–10 cars or light trucks;
• Main propulsion: 2 × 350–400 kW diesel engines;
• Service speed: ~11–12 knots;
• Auxiliary loads: Minimal, with basic HVAC and lighting.

Due to the vessel size and limited service frequency, bunkering is infrequent, and maintenance often occurs in the port of Chios. Operating costs are offset by public subsidies, while tariff revenue remains low due to limited demand elasticity.

Compared to the Salamis–Perama route, the electrification of the Chios–Oinousses ferry line involves more complex technical and operational constraints. The longer sailing distance of approximately 8.5 nautical miles necessitates greater onboard energy storage, which increases both weight and capital cost. Infrastructural limitations on the island of Oinousses—particularly the absence of shore power facilities—add to the challenge. Moreover, the route’s low passenger and vehicle volume restricts the ability to leverage economies of scale, while harsh winter sea conditions require conservative engineering margins to ensure operational reliability.

Despite these constraints, the route remains a viable candidate for partial electrification using hybrid-electric propulsion. A diesel-electric configuration, enhanced with battery storage, allows for zero-emission maneuvering near ports and during off-peak operating periods. Simulations conducted within the framework of the ELECTRA-GR project indicate that a battery capacity in the range of 600 to 800 kWh could cover as much as 50% of the vessel’s total annual energy demand, depending on the chosen operational profile.

Operationally, the vessel could recharge overnight while berthed in Chios, where the electrical grid is more resilient and capable of supporting such loads. In contrast, Oinousses could be outfitted with a low-voltage charging point, sufficient for auxiliary energy support even in the absence of a high-capacity fast charging system.

The electrification of the Chios–Oinousses ferry route faces several infrastructure and policy-related obstacles that must be addressed to enable successful implementation. A primary technical barrier is the limited energy infrastructure on Oinousses, which is not connected to the mainland electricity grid. Instead, the island relies on a standalone diesel generator, rendering it currently unsuitable for high-power vessel charging. In addition, the port lacks the necessary equipment to support automated or semi-automated charging operations, and there is no provision for real-time energy monitoring or smart load management.

Institutionally, Greece does not yet have established technical standards tailored to the electrification of ports serving small island communities. This regulatory gap adds uncertainty and slows project development timelines. Moreover, the design of public service obligation (PSO) subsidies fails to incorporate environmental criteria or incentives for technological innovation, which limits the attractiveness of deploying hybrid or fully electric vessels on subsidized routes.

Nevertheless, these barriers are not insurmountable. Targeted investments in renewable microgrid systems on Oinousses—such as photovoltaic installations integrated with battery storage—could provide a locally sustainable solution for both community energy needs and low-speed ferry charging. According to Reference [12], such systems are increasingly viable for small islands, especially when designed to match maritime and residential energy demands.

Furthermore, the development of a specialized “electric PSO” tendering framework could enhance policy alignment. This would allow environmental performance and electrification commitments to be embedded as criteria in route concessions, in line with EU state aid rules. Such an approach could help catalyze private investment and signal institutional support for zero-emission shipping in remote island areas.

Despite its relatively small scale, the electrification of the Chios–Oinousses ferry route offers several significant co-benefits that extend beyond the immediate operational context. One of the most direct advantages is the improvement in local air quality and the reduction in noise pollution at the port of Oinousses, which would enhance the living conditions for residents and visitors alike. In parallel, the project would serve as a national pilot for the electrification of public service obligation (PSO) ferry routes, showcasing technical feasibility and policy innovation in the context of remote island services.

Additionally, integrating the ferry with local renewable energy sources could reduce Oinousses’ dependence on imported fossil fuels, contributing to greater energy autonomy. This integration would also enhance the resilience of the island’s overall energy supply system, with potential synergies between maritime transport needs and community energy demand.

The implementation of such a project would bolster the environmental credentials of both the ferry operator and the local or regional authorities involved, aligning them with broader European goals for sustainable transport and climate neutrality. It would also support the long-term viability of small-island ferry services, many of which are increasingly threatened by rising operating costs, aging vessels, and limited commercial attractiveness.

Importantly, the Chios–Oinousses initiative could pave the way for replicating similar solutions on other PSO routes with comparable characteristics—such as Lipsi–Leros or Kastellorizo–Rhodes—thus amplifying its strategic relevance and demonstrating the scalability of low-emission maritime mobility in the Aegean and beyond.

3.3. Technological and Industrial Capacity in Greece

Greece possesses a historically significant but currently underutilized shipbuilding sector. The majority of coastal passenger ferries, particularly those operating on short-distance lines, have been constructed in domestic shipyards such as Perama, Elefsis, and Chalkis. These yards have demonstrated capability in producing steel hulls, basic vessel outfitting, and modular retrofitting for propulsion and deck systems. However, limited experience exists in integrating high-voltage electric propulsion systems, battery modules, or energy management systems, reflecting the low domestic demand for electrified vessels to date.

Despite this, recent projects such as the Sikania II hybrid ferry for the Salamis–Perama route signal a shift toward more technologically advanced configurations. Kanellos Shipyards, which led the project, incorporated both battery-electric and solar energy components into the vessel, supported by collaboration with international component suppliers [20]. This illustrates a growing readiness to engage in system integration and hybrid design, provided appropriate incentives and technology transfer mechanisms are in place.

Although Greece possesses the capacity to undertake hull construction and mechanical outfitting for small passenger vessels, it currently lacks domestic manufacturing capabilities for several key components essential to ferry electrification. Critical elements such as lithium-ion battery modules, battery management systems (BMS), high-efficiency electric motors, and associated power electronics, including converters, inverters, and high-voltage switchboards, are not produced locally. Likewise, shore power charging equipment and automation interfaces must be sourced from specialized suppliers abroad, mainly in Northern Europe, Asia, or North America.

This dependence on foreign Original Equipment Manufacturers (OEMs) limits the autonomy of Greek shipyards, which are often excluded from early-stage design decisions and technical specifications during system procurement. Consequently, domestic construction projects involving electrified vessels are exposed to higher lead times, potential supply chain disruptions, and coordination inefficiencies. Such factors may complicate scheduling, increase budget uncertainty, and reduce the competitiveness of local construction efforts compared to better-integrated international shipbuilding hubs.

In terms of technical risks, battery-electric vessel deployment in Greece must address key safety, infrastructure, and operational considerations. Battery thermal management and fire protection systems must align with DNV and IMO regulations, especially for newly built ferries with large-capacity battery packs. From an infrastructure perspective, insufficient port grid capacity, particularly on non-interconnected islands such as Oinousses, could impede reliable charging unless complemented by energy storage or RES-based microgrids. Operationally, variations in vessel schedules, weather conditions, and energy consumption require robust energy planning and route-specific design adaptation. These risks have been reflected in the differentiated electrification strategies examined in this study.

In addition, the technical know-how required to integrate these complex systems remains underdeveloped in the local maritime industry. Expertise in areas such as thermal management of batteries, system redundancy design, electromagnetic compatibility (EMC) shielding, and compliance with classification society requirements is still evolving. This skills gap, particularly in marine electrical engineering, control systems integration, and digital monitoring technologies—represents a significant bottleneck for the scalable deployment of battery-electric or hybrid-electric vessels within Greece’s shipbuilding ecosystem.

The readiness of port infrastructure is a critical enabler for vessel electrification. In Greece, cold ironing or alternative maritime power (AMP) infrastructure exists only at a few commercial ports (e.g., Piraeus, Heraklion) and is designed primarily for cruise ships or Ro-Ro vessels. Small island ports and municipal terminals—such as Oinousses, Aegina, or even parts of Perama—lack the physical space, electrical capacity, or institutional governance to support high-power vessel charging.

Grid constraints, particularly in non-interconnected islands, limit the deployment of fast-charging stations unless accompanied by local energy storage or microgrid upgrades. In some cases, renewable energy integration (e.g., PV + BESS) could offer viable, scalable alternatives, but these require significant upfront investment and coordination between the port authority, Distribution System Operator (HEDNO), and private stakeholders.

The Greek academic and research ecosystem, particularly departments of naval architecture, shipping, and electrical engineering, has shown increasing engagement with green maritime technologies. Institutions such as the National Technical University of Athens, the University of the Aegean, the University of West Attica, and the National and Kapodistrian University of Athens have undertaken research initiatives on battery-electric ships, alternative fuels, and digital ship systems under national and European funding schemes.

However, the link between academia and industry remains fragmented. Technology demonstration projects, dual training programs, and pilot vessel deployments are limited, and knowledge transfer mechanisms are insufficiently institutionalized. This could be supported through the establishment of a dedicated innovation cluster that brings together public agencies, shipbuilders, technology providers, and research institutions, building upon existing entities and platforms such as the Hellenic Institute of Marine Technology, the Hellenic Association of Naval Architects, the Hellenic Marine Equipment Manufacturers & Exporters, the Blue Growth Initiative, and EU-funded programs like Horizon Europe and the Waterborne TP Partnership. These initiatives offer valuable institutional knowledge and collaborative frameworks that can facilitate technology transfer, testing infrastructure, and the upskilling of human resources in support of green maritime transitions.

Despite existing limitations in domestic manufacturing, systems integration capacity, and port infrastructure readiness, Greece possesses several comparative advantages that could be strategically leveraged to advance ferry electrification. One notable strength is the geographic proximity between local shipyards and key ferry routes, which facilitates efficient retrofitting, reduced vessel downtime, and streamlined access to follow-up maintenance. Additionally, the structure of the Greek coastal shipping network—with many short-distance, high-frequency lines and public service obligation (PSO) routes—presents strong underlying demand for the deployment of low-emission vessels.

Greece also benefits from an established maritime labor pool, which, with the support of targeted training and certification programs, could be reskilled to support the emerging needs of electrified fleets and port energy systems. Furthermore, ongoing investments in renewable energy, particularly in insular regions pursuing energy autonomy, create natural synergies for the integration of vessel charging with clean power generation and smart grid technologies.

Another important enabler lies in the country’s access to European Union and European Economic Area (EEA) funding mechanisms. These instruments, including the Connecting Europe Facility and Innovation Fund, offer financial support for first-of-a-kind projects and could play a catalytic role in overcoming initial capital and technology risk barriers.

However, to fully realize these opportunities, Greece must address several persistent constraints. The absence of a stable and coordinated policy framework for maritime decarbonization impedes long-term investment planning. Weak inter-ministerial coordination across transport, energy, and shipping portfolios further complicates regulatory clarity and implementation. Finally, delays in the modernization of port infrastructure and grid capacity, particularly in secondary and island terminals, remain a significant bottleneck for large-scale electrification efforts.

3.4. Legislative and Policy Framework for Ship Electrification in Greece

The electrification of maritime transport is increasingly embedded in the European Union’s climate and transport policy, particularly through the European Green Deal, the Fit for 55 package, and the Sustainable and Smart Mobility Strategy. The FuelEU Maritime Regulation (EU 2023/1805), which enters into force in January 2025, introduces binding limits on the greenhouse gas intensity of energy used on board ships. It also mandates the use of onshore power supply (OPS) for container and passenger ships at major EU ports by 2030.

Complementary instruments such as the Alternative Fuels Infrastructure Regulation (AFIR) and the revised Trans-European Transport Network (TEN-T) Regulation promote the deployment of OPS and zero-emission technologies in ports, particularly those included in the TEN-T core and comprehensive networks [25].

Although these instruments primarily target larger commercial ports and long-distance shipping segments, they are expected to have spillover effects on coastal and island ferry operations, especially where vessels call at ports of national or regional importance.

In Greece, the legislative environment supporting the electrification of ships and port infrastructure is still at an early stage. While national commitments to maritime decarbonization exist, particularly under the National Energy and Climate Plan (NECP) and the Long-Term Strategy for 2050, there is currently no dedicated law or ministerial decision regulating the use of electric vessels or OPS in coastal shipping.

All maritime PSO schemes currently operating in Greece follow a conventional public subsidy model, focused exclusively on ensuring minimum connectivity and service levels, with no differentiation based on environmental performance. Recent policy analyses of the Island Transport Equivalent (ITE) confirm that, although it has improved affordability and access for island residents, it has yet to integrate environmental innovation or green conditionality into its design [27].

At the European Union level, a range of policy instruments has been introduced to support the decarbonization of the maritime sector [1]. The European Green Deal sets the overarching goal of achieving net-zero GHG emissions by 2050, while the FuelEU Maritime regulation and the inclusion of shipping in the EU ETS introduce both regulatory and market-based instruments. Despite these initiatives, Greece has yet to formulate a comprehensive national strategy for electrifying its fleet and ports, underscoring the need for legislative reforms and investment mechanisms modeled after international best practices [28].

A major constraint that emerged from stakeholder interviews and consultation workshops is the fragmented governance framework of Greek coastal shipping. Key responsibilities relevant to ferry electrification are dispersed among multiple authorities, creating procedural complexity and slowing down decision-making. The Ministry of Maritime Affairs and Insular Policy holds the mandate for ferry route tenders, vessel registration, and overall port governance. Meanwhile, national energy planning and electricity grid infrastructure fall under the jurisdiction of the Ministry of Environment and Energy. Port development projects are managed by a combination of the Regulatory Authority for Ports (RAP) and regional port funds, while the Hellenic Electricity Distribution Network Operator (HEDNO) oversees electricity distribution at the local and island levels.

This institutional fragmentation poses a serious obstacle to the timely preparation and implementation of electrification projects. In particular, pilot schemes that depend on the seamless coordination of energy, transport, port, and environmental authorities are vulnerable to bureaucratic delays, inconsistent priorities, and misaligned regulatory frameworks. Overcoming this challenge will require the establishment of integrated governance mechanisms and a clear institutional roadmap that unifies roles and accelerates cross-sectoral collaboration.

Despite the presence of multiple institutional and technical barriers, the Greek government has recently shown increasing interest in promoting sustainable maritime transport. This shift is reflected in several policy instruments, including the inclusion of “Green Ports” projects under the Recovery and Resilience Facility (RRF), which may finance cold ironing demonstration pilots in selected ferry terminals. Additionally, regional Smart Specialization Strategies (RIS3) provide an opportunity to fund electrification feasibility studies and small-scale infrastructure improvements. At the policy design level, proposals for the development of “green PSO schemes” have emerged, aiming to incorporate environmental performance into the evaluation of subsidized ferry routes.

Building on these policy signals and the insights generated through the ELECTRA-GR project, a coordinated set of regulatory and financial measures is recommended to accelerate the electrification of coastal shipping. These include the adoption of a national strategy for maritime electrification, fully aligned with Greece’s National Energy and Climate Plan (NECP) and anchored in a dedicated roadmap for coastal fleet decarbonization. Technical standards and certification procedures for onshore power supply (OPS) systems and electric propulsion vessels should be introduced, in close cooperation with the European Maritime Safety Agency (EMSA) and recognized classification societies.

To support fleet transition in public service routes, the current PSO tender framework must be updated to include environmental criteria, such as emissions thresholds or bonus points for low- or zero-emission vessels. Moreover, the simplification of permitting processes and the designation of a lead coordinating authority would reduce bureaucratic hurdles and accelerate project execution. Targeted funding mechanisms should also be developed to leverage available instruments such as the EEA/Norway Grants, the Just Transition Fund, and EU Cohesion Policy funds.

Altogether, these policy recommendations aim to foster stronger alignment between national decarbonization goals, European regulatory mandates, and industry innovation efforts. At the same time, they seek to build domestic capacity for the design, deployment, and maintenance of zero-emission ferry systems, thus positioning Greece as a credible player in the emerging green maritime economy.

Nevertheless, a significant step toward addressing the existing regulatory gaps is a draft Presidential Decree currently under public consultation, which seeks to establish a comprehensive framework for the licensing and installation of shore-side charging systems in Greek ports. The draft regulation defines competent authorities, technical requirements, safety standards, and permitting procedures for electric power infrastructure serving ships. Its adoption would provide legal certainty and streamline the development of port electrification projects, supporting the objectives of the national climate law and maritime decarbonization strategy.

3.5. Cost–Benefit and Environmental Impact Assessment

The ELECTRA-GR project conducted a comprehensive cost–benefit and environmental impact assessment for the electrification of two selected ferry routes—Salamis–Perama and Chios–Oinousses—using a structured, scenario-based comparative approach. The analysis encompassed the capital and operational costs of electric propulsion systems, energy storage solutions, and shore-side charging infrastructure, along with potential savings arising from reduced fuel consumption and lower maintenance requirements.

Supporting evidence from similar studies on inland waterway vessels indicates that the electrification of marine transport becomes increasingly competitive when total lifecycle emissions and the durability of onboard power systems are factored into the evaluation, particularly in contexts with favorable policy support and electricity pricing structures [29].

The assessment compared a baseline scenario involving continued operation with conventional diesel propulsion to one or more electrification scenarios, which included both fully battery-electric and hybrid-electric vessel configurations. Each scenario was analyzed over a 15-year time horizon, capturing both capital expenditures (CAPEX) and operational expenditures (OPEX).

Environmental impacts were assessed based on key indicators, including carbon dioxide (CO₂) emissions, nitrogen oxides (NO_x), particulate matter (PM) emissions, and the composition of the energy source mix. Economic metrics such as the Net Present Value (NPV) and the Payback Period (PBP) were also calculated, incorporating realistic discount rates and technical assumptions derived from vendor discussions, stakeholder consultations, and recent academic and industry literature [30].

The electrification of ferry services requires significant upfront capital investments, which vary depending on whether a vessel is newly built or retrofitted. For the Salamis–Perama route, full electrification of a newly built Ro-Ro ferry, including shore charging infrastructure and auxiliary systems, was estimated to require a total capital expenditure (CAPEX) of approximately €6.2 million. This includes €4.2 million for vessel construction, €1.6 million for battery systems, and €400,000 for portside charging infrastructure. In comparison, a conventional diesel newbuild was estimated to cost €4.8 million, highlighting a CAPEX premium of €1.4 million for the electric configuration.

Annual operational expenditure (OPEX) for the electric vessel was projected at €160,300, representing a 35% reduction compared to the €248,000 annual OPEX of a conventional diesel vessel. These savings stem from lower energy costs, reduced fuel consumption (with an estimated 70% diesel substitution), and minimized maintenance requirements for electric propulsion systems.

In the case of Chios–Oinousses, which was assessed as a candidate for hybrid-electric retrofit, the required CAPEX amounted to €2.5 million, including €1.0 million for the battery pack, €0.5 million for the electric drive and integration, and €1.0 million for auxiliary systems and conversion works. This represented a moderate CAPEX increase over a conventional retrofit. However, OPEX savings were relatively limited (~20%) due to lower route utilization and fewer sailings. The hybrid vessel’s design aimed to achieve zero-emission operation in port areas and partial substitution of diesel during cruising.

Battery system costs were estimated at approximately €800–1000/kWh, inclusive of battery management systems (BMS), thermal protection, and installation. Charging infrastructure costs depended on port configuration and power availability, with fast-charging systems exceeding €250,000 when grid upgrades were required.

Finally, grid readiness was identified as a critical investment area. In Salamis–Perama, port substations could accommodate the expected vessel loads (~1.5 MW), but some reinforcement was recommended. In Oinousses, the absence of a high-capacity grid required consideration of local energy storage or RES-based microgrids to support limited charging capacity.

Table 1. Key Cost and Technical Parameters of Electrified Ferry Scenarios.

Parameter	Salamis–Perama (Electric Newbuild)	Chios–Oinousses (Hybrid Retrofit)
CAPEX—Conventional Vessel (€M)	4.8	Not specified
CAPEX—Electrified Option (€M)	6.2	2.5
Breakdown—Vessel Construction (€M)	4.2	–
Breakdown—Battery Systems (€M)	1.6	1.0
Breakdown—Port Infrastructure (€M)	0.4	0.5 + 1.0 (aux. systems)
Battery Capacity (MWh)	1.2	0.6
Annual OPEX—Conventional (€)	248,000	230,000
Annual OPEX—Electrified (€)	160,300	Approx. 184,000
OPEX Reduction (%)	35%	20%
Grid Readiness	Substation upgrade recommended	Local RES microgrid needed

presents a comparative overview of the technical and financial parameters for the two case study routes analyzed in the ELECTRA-GR project. It includes capital and operational expenditure estimates for both the conventional and electrified scenarios.

The analysis considered multiple streams of benefits associated with ferry electrification. One of the most significant was fuel cost savings, projected based on future price trends for both diesel and electricity. Additional economic value was derived from the reduction in greenhouse gas (GHG) emissions and air pollutants, including nitrogen oxides (NO_x) and particulate matter (PM), with the environmental gains monetized using external cost factors recommended by the European Union. Maintenance-related savings also emerged as a key advantage, as electric motors and battery systems typically require less frequent and less intensive servicing compared to conventional diesel engines.

Beyond these quantifiable benefits, the electrification of ferry services also contributes to reduced noise and vibration levels, improving passenger comfort and enhancing environmental quality in port-adjacent communities [31]. Evaluation of transition towards zero emission commuter ferries: Comparative Analysis of Fuel-based and Battery-based Marine Propulsion System from financial and environmental perspectives, though these aspects were not monetized in the current analysis.

Moreover, electric propulsion enhances long-term regulatory compliance, mitigating the risk of exposure to future penalties or operational restrictions under increasingly stringent EU decarbonization policies [1].

The monetized environmental benefits were especially pronounced in the Salamis–Perama case, where the switch to electric propulsion was estimated to reduce annual CO₂ emissions by more than 900 tons, alongside significant NO_x and PM reductions. In contrast, the Chios–Oinousses route yielded more modest annual CO₂ savings, amounting to less than 100 tons, reflecting the route’s lower frequency and overall energy demand.

The annual benefit streams for the two case study routes—Salamis–Perama and Chios–Oinousses—are summarized in

Table 2. Annual Benefit Streams by Route.

Benefit Stream	Salamis–Perama	Chios–Oinousses
Fuel Cost Savings (€)	€180,000	€45,000
Maintenance Cost Savings (€)	€40,000	€10,000
CO2 Reduction (tons/year)	900	85
Monetized CO2 Reduction (€)	€108,000	€10,200
NOx/PM Reduction (tons/year)	5.5	0.7
Monetized NOx/PM Reduction (€)	€27,500	€3500
Noise/Vibration Reduction	Yes (non-monetized)	Yes (non-monetized)
Improved Regulatory Compliance	Yes (non-monetized)	Yes (non-monetized)

. The estimates incorporate projected fuel and electricity prices, energy use profiles, emission factors, and maintenance differentials based on vendor data and literature benchmarks.

The economic viability of ferry electrification projects is strongly influenced by capital and operational expenditure patterns, route utilization, fuel prices, and monetized environmental benefits. In the base case for the Salamis–Perama route, full electrification of a newly built Ro-Ro ferry yields a favorable financial profile despite the CAPEX premium over a conventional diesel vessel. Annual savings of approximately €180,000 in fuel and €40,000 in maintenance, combined with monetized environmental benefits of over €135,000, result in a projected NPV of €1.25 million over a 15-year horizon (discount rate: 4%). The payback period is estimated at 7.5 years, primarily driven by high-frequency service and substantial diesel displacement.

In contrast, the Chios–Oinousses hybrid retrofit—serving a low-demand PSO route—exhibits weaker economic performance. Despite moderate fuel and maintenance savings, the lower route utilization constrains the annual benefit stream to under €70,000. Combined with a retrofit CAPEX of €2.5 million, this results in a negative NPV of approximately −€1.69 million, and a payback period exceeding 15 years, rendering the project non-viable without public support.

A sensitivity analysis was performed using the One-At-A-Time (OAT) method, examining the impact of fluctuations in diesel prices, electricity tariffs, battery system CAPEX, and CO₂ pricing. For Salamis–Perama, an increase in diesel prices to €1.65/L improved annual fuel savings by over €15,000, marginally increasing NPV. Similarly, lower electricity prices (€0.18/kWh) and a 20% battery cost reduction each improved NPV by ~€100,000–200,000. The combination of favorable conditions across all variables could raise the project’s NPV to over €1.6 million, bringing the payback period below 6.5 years.

For Chios–Oinousses, while improved conditions reduced the negative NPV, they were insufficient to render the investment profitable without grants. The best-case scenario—combining high diesel prices, low electricity tariffs, and reduced battery CAPEX—yielded an NPV range of −€1.1 to −€1.3 million. These results reinforce the importance of tailored grant mechanisms or “green PSO” incentives for electrification of remote island services.

A comparative synopsis on economic viability and sensitivity analysis for the two ferry electrification scenarios is presented in

Table 3. Economic Viability and Sensitivity.

Parameter	Salamis–Perama (Electric Newbuild)	Chios–Oinousses (Hybrid Retrofit)
CAPEX (€)	6,200,000	2,500,000
Annual OPEX Conventional (€)	248,000	230,000
Annual OPEX Electrified (€)	160,300	184,000
Fuel Cost Savings (€)	180,000	45,000
Maintenance Savings (€)	40,000	10,000
Monetized Environmental Benefits (€)	135,500	13,700
Total Annual Benefit (€)	355,500	68,700
Base Case NPV (15 years, 4%) (€)	1,250,000	−1,690,000
Payback Period (years)	7.5	>15
Best-Case NPV (Sensitivity) (€)	1,600,000	−1,100,000
Viability Without Grants	Yes	No

.

The parameters selected for the sensitivity analysis reflect key cost and financial drivers likely to influence the economic performance of electrification projects. Their test ranges were chosen based on relevant literature, market trends, and policy uncertainty, ensuring the robustness of results under varying assumptions.

Future reductions in battery costs—currently projected at an annual decrease of 5–7% due to economies of scale, improved chemistry, and manufacturing efficiencies—could significantly improve the payback performance of fully electric ferry investments. For the Salamis–Perama case, a 30% decline in battery system cost would reduce total CAPEX by approximately €0.5 million, potentially shortening the payback period from 7.5 to around 6 years, assuming OPEX and benefit streams remain constant. In parallel, increases in battery energy density would reduce the onboard volume and weight penalty, further improving vessel efficiency.

For low-traffic routes such as Chios–Oinousses, the break-even analysis suggests that economic feasibility without subsidies becomes achievable only if CAPEX for retrofit components (batteries, integration systems) decreases by more than 40% and if diesel prices rise significantly. Alternatively, increases in service frequency, vessel utilization, or coupling with RES-based charging (resulting in lower electricity cost and higher monetized environmental benefits) could help reach economic viability thresholds without the need for public support mechanisms.

Beyond vessel-level economics, the project also examined broader system-wide impacts. One key finding was the potential for electrified ferry operations to contribute to a reduction in diesel imports, thereby enhancing national energy security. Grid impact assessments indicated that the moderate power loads required for ferry charging—typically in the range of 1.2 to 1.5 megawatts—could be supported at larger ports such as Perama with minimal infrastructure reinforcement.

However, in more remote or less developed locations like Oinousses, integration with the local grid would necessitate the deployment of complementary technologies such as stationary energy storage systems or microgrid solutions. These investments would not only enable electrification but also enhance long-term sustainability and energy resilience on the islands.

In addition to these infrastructural considerations, the early deployment of electrified ferries holds strategic value as a demonstration effort. Such pilot projects could help reduce perceived technological risks, build stakeholder confidence, and catalyze wider industrial modernization efforts across Greek shipyards and port facilities.

4. Discussion

4.1. Strategic Pillars for Electrifying Greek Coastal Ferries

The electrification of short-distance ferry services in Greece presents both a critical decarbonization opportunity and a complex implementation challenge. Based on the findings of the ELECTRA-GR project, this study confirms that electrification is technically feasible, economically promising—particularly for high-frequency routes—and environmentally impactful, yet it requires targeted interventions across infrastructure, regulatory frameworks, and industrial capacity.

The findings of the two case studies reflect the differentiated challenges and opportunities across Greece’s short-sea network. By selecting two distinct operational contexts, one high-frequency route suitable for full electrification and one lower-intensity route better aligned with hybrid retrofitting, the analysis aligns with the study’s broader objective of exploring implementation pathways that are responsive to real-world diversity in vessel profiles, port infrastructure, and energy readiness. Rather than comparing the two cases on equal terms, their juxtaposition is intended to inform differentiated strategic choices and policy designs. The analysis of the Salamis–Perama and Chios–Oinousses routes revealed that while both benefit from emissions reductions and operational cost savings, only high-demand routes achieve investment viability without direct public support. The results point to a need for differentiated strategies: self-sustained electrification in dense corridors and state-supported pilots in less trafficked, socially vital connections.

From a policy and governance perspective, the current legislative and institutional landscape in Greece is not yet conducive to large-scale adoption of electric vessels. Fragmented responsibilities, lack of technical standards, and absence of financial incentives hinder innovation and increase project risk. Responsibilities are distributed across multiple agencies: the Ministry of Maritime Affairs and Insular Policy oversees vessel safety, route planning, and port operations, while the Ministry of Environment and Energy governs grid regulation and electricity infrastructure. Port development initiatives fall under the jurisdiction of port authorities or regional port funds, and energy distribution to islands is managed separately by HEDNO. As a result, permitting for shore-side charging, infrastructure investments, and operational licensing require disjointed approvals, often resulting in delays and inconsistent technical standards. These barriers underscore the necessity of a coordinated national strategy that aligns environmental goals with transport, energy, and industrial policy.

Internationally, centralized coordination models offer valuable lessons. In Norway, the state-owned Enova acts as a single coordination point, bridging maritime, energy, and port interests by administering funding and issuing technical guidance. Adopting a similar lead-agency approach in Greece could consolidate responsibilities and accelerate implementation.

The deployment of first-mover projects—such as the electrification of the Salamis–Perama route—can play a pivotal role in reducing perceived technological and financial risks, thereby establishing proof of concept and catalyzing broader market uptake. This aligns with best practices observed in Norway, where early pilot programs significantly de-risked the adoption of electric ferry systems [6]. To support long-term planning and adaptive policy responses, it is also essential to develop robust monitoring and evaluation frameworks capable of assessing performance, measuring emissions reductions, and informing future scaling decisions.

The successful implementation of the proposed electrification strategy necessitates a coordinated policy approach involving both public and private sector stakeholders. To achieve this, policymakers should consider embedding vessel electrification within a broader national maritime-energy transition framework, ensuring institutional support and cross-sectoral alignment [3].

Although Norway offers a useful reference point, direct replication of its ferry electrification model in Greece should be approached with caution. Norway benefits from centralized maritime policy coordination, substantial public investment in green infrastructure, and long-standing industrial experience in electric shipbuilding. In contrast, Greece faces fragmented regulatory authority, limited shipyard readiness, and more constrained fiscal capacity. These institutional and economic differences necessitate a context-specific strategy, tailored to local capabilities, governance structures, and investment frameworks.

In this context, Greece may adopt a comprehensive national strategy built on five strategic pillars: shipyard modernization, regulatory harmonization, infrastructure investment, financial tools, and capacity building. These pillars address both the technical and institutional gaps currently hindering progress.

To facilitate a structured and scalable transition toward low-emission ferry operations, the ELECTRA-GR project proposes a five-pillar implementation strategy.

First, shipyard modernization and the development of technical competence are essential. This includes supporting shipyards through grants or tax incentives to acquire the necessary tools and skills for electric vessel construction and retrofitting. Partnerships between domestic builders and foreign Original Equipment Manufacturers (OEMs) should be encouraged to enable technology transfer. Additionally, certification tracks for system integrators and marine electricians need to be developed in alignment with standards established by DNV and EMSA.

Second, the creation of a national regulatory and standards framework is critical. Technical guidelines should be established for vessel battery systems, charging connections, and onboard and shoreside safety measures. Environmental performance criteria must be integrated into future ferry procurement processes and tenders for public service obligation (PSO) routes. To streamline implementation, a lead authority should be assigned responsibility for overseeing permitting procedures and standardization efforts.

Third, infrastructure planning must prioritize port electrification. Investments should be directed toward shore power and charging station installations at high-traffic terminals such as Perama, Rafina, and Aegina. This requires comprehensive grid assessments and the promotion of co-investment schemes involving the Hellenic Electricity Distribution Network Operator (HEDNO) and port authorities. For non-interconnected islands, synergies with renewable energy sources (RES) and local energy storage systems should be explored to support sustainable vessel charging solutions.

Fourth, the establishment of coherent funding frameworks and market-based mechanisms is necessary. Ferry electrification should be integrated into national and regional plans under the Recovery and Resilience Facility (RRF) and the Just Transition Mechanism. EU-level funding opportunities, such as the Connecting Europe Facility (CEF) for Transport and the LIFE Clean Energy Transition program, should also be leveraged. Furthermore, new green PSO schemes could be introduced to reward zero-emission operation by providing favorable scoring or enhanced subsidy rates.

Finally, capacity building and stakeholder engagement are vital for long-term success. Targeted training programs should be launched for seafarers, port technicians, and maritime planners. Collaboration between research institutions and industry can be fostered through innovation clusters or demonstration projects. An inclusive and ongoing dialogue must be maintained with ferry operators, classification societies, and civil society to ensure that incentives are aligned and expectations clearly communicated across all stakeholders.

By integrating these priorities into a cohesive national strategy, Greece can accelerate its transition to clean coastal shipping, align with European decarbonization goals, support the emergence of a competitive domestic green maritime sector, and position itself as a regional leader in green maritime innovation [1,27].

Figure 1 depicts the proposed strategic pillars outlining key actions under each pillar, serving as a guide for policymakers, industry stakeholders, and funding bodies to plan and sequence interventions effectively.

4.2. A Roadmap for Ferry Electrification in Greece

Building on the techno-economic findings of the current study and the strategic potential of hybrid-electrification in Greek coastal shipping, a targeted set of actions is proposed to ensure the successful deployment and broader replication of the ferries’ electrification. These actions are designed to bridge the gap between concept validation and full-scale implementation, while aligning with national climate targets and European decarbonization frameworks.

First, the preparation of a comprehensive technical feasibility study is imperative. This study should deliver design-level engineering documentation for the retrofit, integrating energy system modeling, electric drive selection, battery capacity optimization, and onboard safety provisions. Deliverables should meet the standards required by classification societies, laying the groundwork for shipyard execution.

Second, it is essential to initiate the permitting process with the competent national authorities. This includes early engagement with the Hellenic Coast Guard and the Ministry of Maritime Affairs and Insular Policy, as well as with relevant port authorities such as the Piraeus Port Authority S.A. (PPASA) or local port funds. The submission of technical dossiers, environmental assessments, and safety risk evaluations should be pursued in accordance with applicable maritime retrofit and port operation regulations.

Third, the project is well-positioned to seek EU co-financing under instruments such as the Innovation Fund’s Small-Scale Projects Call. Given its demonstrative character and measurable greenhouse gas (GHG) abatement potential, the project aligns strongly with the objectives of the EU Green Deal and the Sustainable and Smart Mobility Strategy. A robust funding proposal should emphasize environmental performance, technological maturity, and replicability. National co-financing and project bundling options should also be explored to strengthen funding leverage.

Fourth, coordination with the national grid operator (HEDNO) is critical to secure adequate grid capacity for vessel charging, particularly in ports such as Chios or Oinousses where grid constraints exist. In parallel, a Power Purchase Agreement (PPA) should be established with a certified renewable energy provider to ensure the system’s reliance on clean energy sources, in line with the project’s decarbonization objectives.

Fifth, following implementation, a structured dissemination strategy should be deployed. This includes publication of technical results, performance data, and economic indicators through industry events, scientific platforms, and dedicated stakeholder workshops. The dissemination effort will maximize the project’s impact by fostering knowledge transfer and facilitating replication across other public service obligation (PSO) routes in the Aegean and beyond.

In summary, the proposed implementation roadmap supports both project maturity and strategic alignment with EU maritime climate policy. It ensures that the ferries’ electrification project does not remain an isolated pilot, but serves as a scalable model for clean innovation in the Mediterranean short-sea shipping sector.

Figure 2 presents the proposed implementation roadmap for the ferries’ electrification project, outlining the sequential steps required for technical, regulatory, financial, and dissemination activities to ensure successful deployment and broader replication.

4.3. Future Research Directions

Building on the findings of this study, several avenues for future research are identified that could further support the electrification of ferry operations in Greece and similar maritime regions. One important area is the lifecycle assessment (LCA) of electric vessels, which would enable a more comprehensive evaluation of their environmental performance by incorporating emissions and resource use across the entire life cycle, including battery manufacturing, vessel decommissioning, and port infrastructure development. In parallel, the integration of advanced digital systems—such as real-time energy management, condition-based monitoring, and predictive maintenance tools—offers substantial opportunities to optimize operational efficiency and extend battery life. The application of digital twin technologies specifically tailored to electric ferries presents a particularly promising field for innovation.

Furthermore, future studies should investigate business models for sustainable operation of green Public Service Obligation (PSO) routes. This includes assessing how dynamic subsidy schemes, carbon pricing, or tradable emissions credits can incentivize private sector engagement on routes that are essential for connectivity but financially marginal. In areas where power grid limitations persist, such as smaller islands, research should also focus on optimizing hybrid configurations that combine batteries with photovoltaic systems, hydrogen fuel cells, or advanced biofuels, taking into account varying energy loads and operational constraints.

Understanding user acceptance and behavioral factors—both from the perspective of passengers and vessel operators—is also critical to ensuring smooth adoption and public support for electric ferry technologies. Finally, there is a need for comparative benchmarking and policy diffusion studies that examine how other Southern European and island nations, such as Italy, Spain, and Croatia, are addressing similar challenges. Identifying adaptable best practices from these contexts could greatly accelerate policy learning and deployment of electrified maritime transport across the Mediterranean.

However, while the present study offers a comprehensive theoretical framework supported by two illustrative case studies, it is important to acknowledge several limitations. First, the economic modeling relies on point estimates and assumptions regarding technological costs and performance, which may evolve over time. Second, real-world implementation challenges, such as regulatory inertia, stakeholder acceptance, and port-specific grid constraints, were only partially captured. Future research should therefore focus on validating the proposed models through pilot demonstration projects, collecting longitudinal operational and cost data, and performing sensitivity analyses to quantify uncertainties. Additionally, further investigation is needed into the system-level impacts of electric ferry integration, such as demand-side management in non-interconnected island grids and potential for vehicle-to-grid (V2G) services. These steps would help bridge the gap between techno-economic feasibility and implementation readiness.

5. Conclusions

This paper has evaluated the feasibility, economic viability, and regulatory context for the electrification of short-distance ferry services in Greece, drawing on the findings of the EEA-funded ELECTRA-GR project and leveraging comparative insights from Norway’s advanced zero-emission ferry program. The analysis confirms that the technical conditions for fully electric or hybrid-electric operation are in place, particularly for high-frequency routes such as Salamis–Perama. Existing shipbuilding and design capabilities within Greek shipyards provide a sufficient starting point for local implementation, although further enhancement is required.

From an economic perspective, electrification is found to be viable on dense routes, especially under favorable electricity tariffs and high vessel utilization. In contrast, less trafficked public service obligation (PSO) routes like Chios–Oinousses necessitate financial support, such as investment subsidies or green procurement schemes, to achieve acceptable returns. The environmental advantages are considerable, as demonstrated by the potential to reduce over 900 tons of CO₂ emissions annually on the Salamis–Perama route alone, alongside reductions in nitrogen oxides (NO_x) and particulate matter.

However, significant challenges persist. These include inadequate shore-side charging infrastructure, the absence of harmonized technical standards and classification protocols, and a lack of institutional leadership to coordinate efforts across ministries, port authorities, and private actors. Furthermore, Greece lacks consistent fiscal or regulatory incentives to accelerate investment in clean maritime technologies.

To address these gaps, the study proposed a five-pillar roadmap for a scalable transition. This includes the modernization of shipyard capabilities, regulatory harmonization aligned with EU directives, targeted investment in port infrastructure, the development of financial support tools, and comprehensive capacity-building initiatives for public and private stakeholders. Collectively, these findings suggest that Greece possesses the strategic foundations to initiate and expand electric ferry operations, provided that a coherent and well-supported national coordination framework is established without delay.

Pursuing these research directions will enrich the scientific basis for sustainable maritime innovation and facilitate the broader transition toward climate-neutral short sea shipping within the European Union and beyond.