Beyond the Grid: Modeling, Optimization and Economic Evaluation of Future Hydrogen Autonomous Home Energy Systems

Abstract

In this work the feasibility of fully autonomous hydrogen homes designed for complete off-grid operation is presented. A detailed mathematical modeling and optimization model is developed to evaluate the technical performance and economic feasibility of hydrogen fuel cell-powered residential systems with no grid connection or fallback. The system integrates primary and standby Proton Exchange Membrane (PEM) fuel cells, multi-day hydrogen storage, advanced power conditioning, and comprehensive controls to achieve reliable year-round power supply. The analysis encompasses a complete 20-year lifecycle cost assessment. The results demonstrate that fully autonomous hydrogen homes achieve 99.85% system availability with 13.1 h of potential downtime annually, providing reliable energy independence. The levelized cost of electricity over the 20-year system lifetime is calculated at 0.4543 US$/kWh at baseline hydrogen prices of 6 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$, substantially higher than grid-connected alternatives. The analysis identifies critical sensitivity to hydrogen pricing and demonstrates that at hydrogen costs below 3 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ (achievable with mature green hydrogen production), competitive payback periods of 12–15 years are possible in high-cost electricity regions. This study concludes that hydrogen-based autonomous homes represent a viable long-term solution for residential energy independence, particularly in remote or off-grid locations where grid connection is impractical or in regions with high electricity tariffs and developing green hydrogen production capacity.

1. Introduction

The global pursuit of sustainable energy solutions and increased energy independence has spurred significant innovation in residential power systems. As concerns over climate change mount and the limitations of traditional grid-dependent infrastructure become more apparent, the concept of autonomous housing is gaining traction [1,2,3]. Among the most current and promising technologies for achieving true energy self-sufficiency is the integration of hydrogen in residential buildings as a means to produce energy [1,4,5,6]. This approach aims to create a fully self-sufficient home, where residential power and heating needs are met without any reliance on the traditional electrical grid.

Hydrogen homes represent a critical and necessary step in the global energy transition. The need for these systems stems from a fundamental challenge posed by traditional energy infrastructure and the limitations of existing renewable technologies. While solar and wind power are essential for decarbonization, their intermittent nature creates a significant gap in reliability and long-term storage [7,8,9]. Referring to Figure 1, by enabling a home to generate and store its own energy in the form of hydrogen, i.e., an all-in-one hydrogen home, these systems aim to address the need for a truly resilient and independent energy supply that can provide power and heat throughout the whole day, while simultaneously reducing a building’s carbon footprint [10,11,12].

Hydrogen autonomous houses represent a shift in residential living, offering the potential for a zero-emission, local energy supply [13,14]. The motivation for off-grid hydrogen homes stems from several critical needs in the global energy transition. First, true energy independence is essential for remote or island communities where grid extension is economically prohibitive or technically infeasible. Second, resilience against grid failures, natural disasters, or geopolitical disruptions is increasingly valued by homeowners. Third, decarbonization of residential energy in remote areas that lack renewable energy integration opportunities can only be achieved through local generation and storage. Finally, in regions with high electricity costs or unreliable grid infrastructure, autonomous systems may provide superior economics compared to grid-dependent alternatives.

Hydrogen offers distinct advantages for autonomous residential systems compared to battery-only approaches as well. While batteries provide excellent short-term storage (hours to days), their cost increases prohibitively for multi-day or seasonal storage requirements [15,16]. Hydrogen, by contrast, can be produced and stored indefinitely at constant efficiency, enabling true seasonal energy storage, whereas Li-ion batteries are known to suffer from both self-discharge and a linear scaling of CAPEX with energy capacity, making long-duration storage economically taxing [17,18,19,20,21]. However, it is important to note that while hydrogen avoids the chemical self-discharge typical of Li-ion batteries, the long-term operational efficiency of domestic systems is governed by the durability of the energy conversion hardware, which consequently impacts the system’s service life and maintenance costs [22].

When hydrogen is needed, fuel cells convert it back to electricity and usable heat with modest electrical efficiency (55%), but these losses can be partly recovered through combined heat and power applications [23,24]. Consequently, hydrogen-based autonomous homes can reliably serve residential loads during extended periods of insufficient renewable generation, a capability critical for year-round operation. However, even with the integration of hydrogen, intermittency issues posed by renewable resources can affect the system and its ability to supply electricity continuously. Issues include reduced overall efficiency and longevity due to frequent on–off cycles and fluctuating power [25,26,27,28]. In addition, even with the integration of hydrogen storage and a smart Home Energy Management System (HEMS), a house may still need to be connected to an external power grid for backup purposes due to prolonged periods of intermittency, e.g., during the winter [29,30]. Moreover, due to the fact that the entire system is a complex integration of different technologies (electrolyzer, fuel cell, storage, inverter, renewable energy production, etc.), it requires a comprehensive and sometimes costly maintenance plan. The issues, combined with current immature hydrogen production and distribution infrastructure, add to the Levelized Cost of Electricity (LCOE). This ultimately means that the LCOE of such a home substantially exceeds current electricity grid rates, making it not a cost-competitive alternative.

On the other hand, as shown in Figure 2, if the household relies on externally supplied hydrogen, both maintenance requirements and associated costs are reduced. The absence of on-site equipment, like electrolyzers, eliminates the need for complex maintenance procedures and safety checks typically required for these components. The fact that electricity is produced via a fuel cell through a constant hydrogen supply eliminates issues of intermittency and associated costs. The remaining maintenance is associated with air filter changes and checks, making it a more manageable undertaking for the homeowner. Overall, the complexity of the system is reduced and the autonomy of the home is sustained as there would be no need for backup connection to the electric grid.

This work develops a comprehensive mathematical and optimization framework to understand the economics of a future off-grid autonomous home that is physically disconnected from the electricity utility infrastructure, with on-site hydrogen storage, by providing a detailed techno-economic evaluation. It aims to examine how residential hydrogen usage can be simplified by outsourcing hydrogen production and storage. Additionally, the proposed home aims to tackle issues of intermittency, autonomy and energy independence, as well as cost-competitiveness in comparison with an electricity grid-connected home. While previous studies on residential hydrogen have focused on fully integrated on-site generation [31,32,33,34], this framework introduces a novel decoupled supply chain perspective. By mathematically formalizing an external procurement model of hydrogen, this study departs from the conventional all-in-one system architecture. This shift in the system boundary allows for a high-fidelity evaluation of the home’s storage and utilization dynamics, independent of the technical complexities and geographic constraints of on-site electrolysis. Consequently, this work provides a new methodological blueprint for quantifying the trade-offs between decentralized energy autonomy and large-scale infrastructure reliance. For avoidance of doubt, the residential system analyzed in this work does not include an on-site electrolyzer or compressor since hydrogen is assumed to be produced off-site and delivered ready-to-use to the home.

In Section 2, a comprehensive literature review is undertaken, presenting the current stages of residential hydrogen and hydrogen autonomous homes, alongside their technical aspects. Section 3 includes current concepts and realized plans for hydrogen homes, including the challenges faced by all-in-one hydrogen homes. Section 4 presents the proposed mathematical model for an off-grid autonomous home with an on-site hydrogen storage, followed by all results and discussion in Section 5. Lastly, Section 6 concludes all the findings and proposes future recommendations.

2. State of the Art in Hydrogen Home Systems

The concept of the hydrogen economy relies on the fact that hydrogen is a versatile energy carrier, complementing electricity and playing a crucial role in decarbonizing sectors that are heavy emitters and difficult to electrify, such as heavy industry and long-haul transportation [35,36,37]. While hydrogen has long been used in industrial processes, its potential as a clean energy vector is only now being fully explored. Different types of hydrogen, often distinguished by a “color” classification, exist based on their production method [38,39]. The vast majority of hydrogen produced today is “gray hydrogen”, derived from fossil fuels like natural gas via steam–methane reforming (SMR), a process that releases significant carbon emissions [40,41]. In contrast, “green hydrogen” is the key to a sustainable hydrogen economy. Green hydrogen is produced through electrolysis with the electricity supplied by renewable sources, resulting in zero carbon emissions [42,43,44]. This makes green hydrogen the most attractive option for sustainability goals in all sectors, as well as residential energy production.

Residential energy systems, primarily built around solar photovoltaic (PV) panels, have become increasingly popular for energy production targeting reduced emissions as well as utility costs [45,46,47,48]. These systems allow for the generation of clean electricity (and potentially its storage) for use during times when sunlight is not adequate for electricity production. However, a significant limitation of these systems is their dependency on weather conditions and the limited storage capacity of batteries. Solar panels only produce power when there is sunlight. Batteries, typically sized for a day or two of backup, depending on the capacity [49,50,51,52], cannot provide the long-term, seasonal storage needed to achieve true energy autonomy, especially in regions with distinct seasonal changes in sunlight. Therefore, while still a field in its primitive stages, research on residential hydrogen systems has been gaining traction. The literature confirms a significant knowledge gap, with a disproportionate focus on hydrogen for transportation compared to its use in homes [53,54,55,56]. However, a growing body of work addresses the technical and economic feasibility of decentralized residential systems [31,32,33,34].

In a hydrogen autonomous home, energy independence should be achieved through a self-contained, closed-loop system that liberates the household from its reliance on the public grid. Based on the current literature, this is thought to be achieved by using renewable energy to produce and store hydrogen, which then fuels the home’s energy needs. The home is considered an all-in-one home as it is not powered by hydrogen alone. It is a hybrid system that intelligently integrates multiple components. Firstly, the system depends on renewable energy generation via a primary renewable energy source, typically solar panels or a small wind turbine [2,3,57,58]. These produce electricity when conditions are favorable, for example, during the day, when there is enough sunlight or wind. During these hours, the home’s immediate power demand is usually met, and therefore any excess power can be partly stored in a short-term battery, in order to ensure the home is completely autonomous and “energy-autarkic” [59,60].

In addition to the short-term battery, any surplus electricity is then diverted to an electrolyzer to split water into its constituent elements (hydrogen gas and oxygen) via electrolysis, as seen in Figure 3. This is the primary hydrogen production method within the all-in-one hydrogen home. The hydrogen produced is referred to as “green hydrogen” as it is produced via renewable energy resources and does not produce any carbon emissions [39]. A study carried out by [61] examined an off-grid PV energy system with a Proton Exchange Membrane (PEM) water electrolyzer for the production of hydrogen. They concluded that the system produced hydrogen at a price range between 3.23 and 5.39 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ depending on the electrolyzer capacity, varying from 2 to 14 kW. The system, however, is modeled for areas of high solar energy, specifically Baghdad, Iraq. This inevitably means that in areas of lower solar energy, intermittency issues are more likely to arise, inhibiting the autonomous nature of the off-grid home.

In addition, there are other methods to produce hydrogen, including SMR and Photoelectrochemical (PEC) Cells. SMR is currently the most widespread and cost-effective method for producing hydrogen [62,63]. The resulting hydrogen is known as “gray hydrogen”; if carbon capture and storage (CCS) technologies can be integrated, the resulting hydrogen is known as “blue hydrogen” as it encompasses a lower carbon footprint. This process requires a continuous supply of natural gas and operates at very high temperatures, making it a centralized, industrial-scale technology. It would negate the core purpose of energy independence and sustainability as it is a fossil fuel-based process that releases carbon emissions. On the other hand, PEC cells are an alternative solution to electrolysis as they represent a long-term, direct solar-to-hydrogen pathway. These devices use specialized semiconductor materials that absorb sunlight and directly split water molecules into hydrogen and oxygen in a single, integrated step, without the need for an external power grid or a separate electrolyzer [64,65]. The process offers the potential for very high efficiency and a low environmental footprint. While PEC technology is still maturing and facing significant challenges related to material costs, long-term durability, overall efficiency and scalability [66,67,68], recent breakthroughs have moved it closer to commercial viability [69,70,71]. Notably, thermally integrated PEC systems have now demonstrated solar-to-hydrogen (STH) efficiencies of up to 20% at the kilowatt scale [72]. However, the fact that this technology also relies on renewable resources poses issues of intermittency and non-continuous production, resulting in the need for a back-up energy source and therefore contrasting with the decentralized purpose of a home.

Irrespective of the hydrogen production method, the produced hydrogen must be compressed and stored in secure tanks. Hydrogen storage is one of the most significant challenges and a key enabler for hydrogen autonomous homes. Unlike batteries, which lose charge over time and are costly to scale for multi-day or seasonal storage, hydrogen can be stored long-term, without any significant energy loss [73,74]. It can therefore act as an energy reservoir for the when solar production is low and demand for heating and electricity is high. Due to the nature of hydrogen gas (i.e., a light gas with low energy density at ambient pressure), it must be compressed or converted to a denser state to be stored efficiently. For residential applications, three primary methods are considered: compressed gas, liquid hydrogen, and solid-state storage.

Compressing hydrogen gas is the most common and mature technology for residential hydrogen storage. It involves very high pressures (350–700 bar), leading to an energy density of 1.5 kWh/L (around 120 MJ/kg), and storage in high-pressure composite tanks [75,76,77]. This is a well-understood, commercially available technology that is relatively simple to implement. These tanks are scalable, meaning they can be sized for the energy needs of an individual home [76,78,79]. However, compressing hydrogen requires a significant amount of energy, which lowers the overall efficiency of the system [78,80]. The tanks can also be large depending on the size of the home, hence requiring a considerable footprint. Despite advanced safety features, high-pressure storage can present safety risks and requires careful handling and monitoring [78].

Liquefying hydrogen is another method used to store it. Hydrogen is cooled to a cryogenic temperature of −253 °C, thereby increasing the energy density (around 2.8 kWh/L, or 142 MJ/kg), allowing more hydrogen to be stored in a smaller volume [76,81]. However, liquefying hydrogen can have drawbacks that make it somewhat impractical for residential use. The liquefaction process is extremely energy-intensive (consuming about 30% of the energy content of the hydrogen [82], and maintaining the extremely low temperature requires complex, heavily insulated cryogenic tanks [78,81,83]. Even when insulation can be improved, a small amount of hydrogen will evaporate over time, or “boil off”, introducing issues of leakage, whereas gaseous storage in high-pressure tanks is known to be exceptionally stable both in terms of leakage and seasonal use [78,83,84,85,86,87,88].

Lastly, solid-state storage involves storing hydrogen by binding chemically or physically, within the structure of a solid material or bound on its surface. If hydrogen is chemically bound, it will produce metal hydrides, which can be obtained when needed via thermal stimulation or hydrolysis [78]. If physically bound, hydrogen gas is physisorbed or chemisorbed to a high surface area substrate: nanostructured materials such as carbon nanotubes and metal organic framework (MOF) systems [89,90]. These methods result in lower storage pressure, thereby reducing safety issues [91]. However, these technologies are still in the early stages of commercial development and can be expensive. Releasing the hydrogen usually requires high temperatures, adding to the system’s complexity and energy consumption, even though heat from the fuel cell can often be used, improving overall system efficiency [78,90,92].

One other important part of the all-in-one hydrogen home is the fuel cell. As mentioned, there is a short-term battery within the system that will discharge first to meet demand, when the renewable energy is affected by intermittencies. However, if more energy is needed especially during the night or throughout winter, the fuel cell will activate. Fuel cells are electrochemical devices that convert the stored hydrogen back into electricity and water, with heat as a valuable byproduct. Unlike a battery that stores a finite amount of energy, a fuel cell produces power continuously as long as it is supplied with fuel. For a hydrogen autonomous home, the most suitable type of fuel cell is the Proton Exchange Membrane (PEM) fuel cell. PEM fuel cells are ideal for residential use due to several key characteristics. Their low operating temperature (65–85 °C) allows for a quick startup and reduces the risk associated with high-temperature operation, making them safer for a residential building [93,94,95]. They are also compact, modular and hence scalable, and individual cells can be combined into a “stack” to meet the specific energy demands of a household [96,97,98,99]. In addition, PEM fuel cells have a high electrical efficiency of about 40–60%, which can be boosted to an overall system efficiency of 80% when waste heat can be captured to heat the home or water, via Combined Heat and Power (CHP) [99,100]. However, unlike the passive self-discharge of electrochemical batteries, the challenges in hydrogen systems are primarily centered on the durability of the conversion hardware. During long-term operation, PEM fuel cells experience a gradual decline in performance due to catalyst migration, electrode degradation, and mechanical stress on the membrane electrode assembly. These degradation pathways not only affect real-world electrical efficiency but also dictate the maintenance cycles and total cost of ownership for domestic hydrogen systems [22,101,102].

Beyond PEM cells, a diverse family of fuel cells exists, each with unique characteristics that make them suitable for different applications, particularly large-scale industrial and utility use. Solid Oxide Fuel Cells (SOFCs) are high-temperature fuel cells that use a non-porous ceramic compound as their electrolyte. They operate at high temperatures ranging from 500 °C to 1000 °C. SOFCs are well-suited for large, stationary power generation and CHP applications in industrial or commercial settings. However, their long startup time and consequent material degradation due to the high temperatures make them impractical for residential use, which requires rapid response to fluctuating energy demands [103,104,105].

Alkaline Fuel Cells (AFCs) are one of the oldest and most mature fuel cell technologies. Potassium hydroxide solution is used as the electrolyte, and operating temperatures are low [106,107,108]. AFCs are highly efficient and can be built with non-precious metal catalysts, potentially lowering costs. However, they are extremely sensitive to carbon dioxide, which reacts with the electrolyte to form carbonates that will ultimately reduce performance [109,110]. This requires a costly and complex air purification system, making them unfeasible for a typical residential building. Phosphoric Acid Fuel Cells (PAFCs) use liquid phosphoric acid as their electrolyte and operate at medium temperatures, around 150 °C to 200 °C [111,112,113]. They are also often used for on-site power generation in hospitals, hotels and office buildings. However, their size, startup time and operating temperature make them unsuitable for an individual home but well-suited for larger commercial or distributed generation applications [114,115,116]. Lastly, Molten Carbonate Fuel Cells (MCFCs) are another form of high-temperature fuel cell, operating at around 650 °C via a molten mixture of carbonate salts as their electrolyte [114,117,118]. Like SOFCs they are highly efficient, particularly in CHP applications. However, they are primarily designed for large-scale power plants and are not practical for a residential setting due to their size and high operating temperature.

PEM cells can also operate as CHP systems, as depicted in Figure 4, efficiently achieving cogeneration of both electricity and heat. The heat produced during the electrochemical reaction within the PEM cells is around 60–80 °C, making it ideal for residential heating and water heating needs [119,120]. A heat exchanger is used to capture this thermal energy, which is then recovered and used accordingly [120]. The integration of CHP in such a system has shown to significantly boost the overall system efficiency to over 80% [121,122,123]. In addition, the only byproducts are electricity, heat and water. This keeps the home not only autonomous but also sustainable and emission-free.

Moreover, CHP systems can be scaled according to the specific needs and size of a home, allowing flexibility and future adaptation if needed [121,124,125,126]. Specifically, micro-CHP systems are small-scale versions of conventional CHP systems, designed for homes and small commercial buildings. In a specific study [30], a home of 180 m² was modeled with an integrated micro-CHP system. It has been shown that the home can operate with high efficiency (more than 85%), with a minimum of 57% self-sufficiency when modeled in the coldest region. As solar radiance increases, or annual heating degree day (HDD) decreases, the yearly hydrogen coverage rate can reach about 120%, meaning that the yearly hydrogen quantity available is 20% higher than the hydrogen quantity consumed by the micro-CHP unit.

Another study [127] determined that between March and October, a 150 m² home with a PEM cell, PV panels and a micro-CHP system can provide its own energy and sell excess electrical energy to the grid (if the PV panel area of more than 33.6 m²), whereas during the winter months, the system needs to utilize the external grid (i.e., not be autonomous) due to the low PV performance. Additionally, a study examining a hybrid system comprising PV solar and a PEM fuel cell and electrolyzer [128], revealed that increasing the amount of hydrogen needs decreases the overall system efficiency. Moreover, variable electrolyzer power consumption was proven to be directly related to changes in the amount of hydrogen required by the fuel cell, which in turn depends on the fuel cell production power. The Levelised Cost of Hydrogen (LCOH) is also seen to be affected by the electrolysis capacity [129], i.e., the lower is the electrolysis capacity, the lower the LCOH.

It is evident that the intermittency of renewable energy sources negatively impacts the autonomy of the home, as well as fuel cell efficiency [28,130,131]. Fuel cells operate most effectively and have a longer lifespan when supplied with a continuous, stable flow of hydrogen and air. When subjected to frequent startups, shutdowns and power fluctuations, they can lead to a drop in efficiency, a decrease in durability and potential system damage. This issue can be solved via a continuous energy and hydrogen supply system, which will in turn provide a reliable and continuous supply of electricity.

An intelligent Home Energy Management System (HEMS) can be also implemented within the home’s system, as visualized in Figure 5. It can be a critical component for maximizing the benefits of all-in-one hydrogen homes as it acts as the brain that optimizes the operation of the system in real time. An intelligent HEMS uses a combination of hardware and software to monitor, control and optimize a home energy supply and demand. Within a hydrogen home, the HEMS manages the entire energy system, i.e., the CHP unit, the renewable energy sources, the energy storage (short-term battery and hydrogen storage), any smart appliances and the connection to the electrical grid, if present [132,133,134]. Typically, a HEMS uses real-time data from all these components, along with external information like electricity prices, weather forecasts, and the homeowner’s usage patterns, in order to make smart, automated decisions [135,136]. For example, when there is excess solar power, the intelligent HEMS will prioritize powering the appliances, followed by the charging of the short-term battery. Once the battery is full, the HEMS will divert the remaining electricity to the electrolyzer to produce and store hydrogen. This sequence of events will prevent wasted energy and therefore create a long-term energy reserve. On the other hand, when there is high energy demand, the HEMS will draw electricity from the most efficient and cost-effective source. Specifically, it will likely use the battery first for immediate power needs. If the battery is depleted and there is no renewable energy being generated, the HEMS will activate the fuel cell to convert the stored hydrogen into electricity to power the home [133,135,137]. The system can also schedule the operation of flexible appliances to run during periods of high renewable energy production or low-cost electricity from the grid (if connected), allowing for a dynamic load management. By selling excess energy back to the grid or participating in demand–response programs, the homeowner can adjust their energy usage in response to grid signals. This benefits not only the homeowner but also the broader electrical grid, aiding the balance of supply and demand [135,138,139]. However, it is important to note that the connection to an external electrical grid negates the autonomous aspect of the home. Overall, the utilization of a HEMS can still provide benefits to any hydrogen home, even if renewable energy is still produced on site and hydrogen is supplied externally.

Within a hydrogen autonomous home, there is the possibility of integrating a Home-to-Vehicle (H2V) system, which is a concept that will enhance energy resilience, efficiency and independence [138,140,141]. These systems allow for the on-site charging of a Battery Electric Vehicle (BEV) with electricity produced by the renewable resources, including an integration of a HEMS in order to allow sufficient energy and electricity management for both the home and vehicle [141]. However, while H2V systems are most commonly discussed in the context of BEVs, the principles and benefits are highly relevant, and in some ways even more impactful, when applied to hydrogen fuel cell electric vehicles (FCEVs). An FCEV, which stores hydrogen as its fuel [37,142], can be seamlessly integrated into this system, with the most significant integration point being the shared hydrogen storage and refueling infrastructure. A hydrogen home with an on-site electrolyzer and storage tank can serve as a personal hydrogen refueling station for the FCEV, especially when there is excess renewable energy to be diverted by the HEMS to the electrolyzer to produce hydrogen. Even if hydrogen is produced externally, the H2V concept remains viable; it can offer higher operational stability as the hydrogen supply is decoupled from local renewable energy fluctuations, provided that a standardized delivery schedule or a buffer in storage is maintained.

The system can also work bidirectionally via the FCEV’s battery as a form of mobile energy storage; in other words, the system becomes Vehicle-to-Home (V2H). When the FCEV is on site, its fuel cell can be used to generate electricity from its onboard hydrogen tank. The intelligent HEMS can also decide when to draw power from the FCEV, especially during power outages, peak demand periods and low renewable production (if present). This integration can provide key benefits for both the home and vehicle. The FCEV acts as a mobile, large-scale energy reserve, providing a supplementary backup power solution, allowing for enhanced energy independence, especially in emergency cases. The presence of an intelligent HEMS also allows for optimal resource utilization, by ensuring all available energy sources are used in the most efficient and cost-effective manner. Lastly, this integration can aid the complete decarbonization of both the residential aspect, as well as transport, as the dependency on fossil fuels and the grid can be minimized.

Overall, the implementation of an all-in-one hydrogen home can allow for partial autonomy, especially in areas that have fluctuating sunlight or wind availability, or have prolonged winter periods. The integration of an intelligent HEMS can aid in optimizing energy utilization; however, the intermittency introduced by renewable resources introduces issues of efficiency and disrupted hydrogen production.

3. Existing Concepts of Hydrogen Homes and Current Challenges

The concept of hydrogen autonomous homes is already being tested and demonstrated in a number of projects around the world. One of the pioneering projects is the Hopewell Project Solar–Hydrogen Residence in New Jersey, USA. It was designed to demonstrate a completely self-sufficient, carbon-free residential energy system. The home meets all of its power needs, including heating and cooling, solely through renewable solar energy and hydrogen. This demonstration home proved the technical feasibility of using hydrogen and renewable resources to power an entire residence back in 2006 [143].

In regard to more recent projects, one such example is the ATCO’s Hydrogen Home in Australia [144]. This demonstration facility showcases a complete hydrogen energy system with solar panels, an electrolyzer and a fuel cell, to provide round-the-clock power. It demonstrates the practical application of hydrogen for residential use, as well as test a range of appliances that run on hydrogen, including a cooktop, hot water system and HVAC setup [145]. This project is directly connected to the larger Clean Energy Innovation Hub (CEIH), which provides the research, production and testing infrastructure to support the home’s operations. The CEIH also produces hydrogen for other applications, such as blending into the natural gas grid and for use in a hydrogen refueling station for FCEVs [146,147]. Currently, the most significant and ongoing advancement is the large-scale hydrogen blending project in the City of Cockburn, which began in late 2022. This project, one of the largest of its kind in Australia, is blending a small percentage of renewable hydrogen (up to 10%) into the existing natural gas network, supplying around 3000 residential and commercial connections [148], thereby demonstrating the feasibility of using existing infrastructure to deliver a cleaner gas to consumers, without requiring changes to their appliances. Another similar project to ATCO’s Hydrogen Home is the SoCalGas Hydrogen Home in the U.S. This project aims to demonstrate the resilience and reliability of a hydrogen micro-grid. The home uses solar energy to produce and store hydrogen, which is then used in a fuel cell to provide power. It also explores blending hydrogen with natural gas for other appliances, at around 20% [149]. In addition, it demonstrates how a hydrogen micro-grid can provide a reliable source of power, especially during power outages or “public safety power shutoffs” [150]. However, the literature has noted issues with material degradation, appliance performance and NOx emission considerations [151,152,153,154], which steer production toward appliance models that are “hydrogen-ready”. In other words, these appliances can run on natural gas now and switch to hydrogen when the infrastructure becomes available [151,152,155,156,157,158].

Irrespective of the realized concepts, the all-in-one hydrogen home faces some crucial challenges. These are mainly attributed to complicated maintenance and integration issues, lack of expertise and economic issues arising from the technical immaturity of such an integrated system. These challenges are summarized in

Table 1. All-in-one hydrogen home challenges.

Challenge	Comments
Maintenance and integration challenges	The entire system, including solar panels, inverters and the control system that manages the flow of energy, has its own maintenance schedule. The complexity of an all-in-one hydrogen home system means that a single point of failure can impact the entire system.
Lack of expertise	The expertise required for these systems is minimal, and the need for specialized knowledge can be very costly. The cost of maintenance, including technical parts and and labor from specialized technicians, can be a factor that will affect the running costs. While the long-term goal is a low-cost, low-maintenance solution, the current stage and complexity of the technology requires a more expert-driven, specialized approach to maintenance.
Specific equipment issues	Electrolyzers, especially PEM electrolyzers, can be affected by impurities in the water, which in turn degrade the electrolyzer’s membrane and components over time, reducing its efficiency and lifespan [159,160,161,162]. In the case of Alkaline Electrolyzers, the liquid electrolyte can accumulate impurities over time and will hence need to be replaced periodically [163,164]. Due to the intermittency of the renewable resources, the resulting frequent on/off cycling of an electrolyzer can cause wear and tear. While modern systems are designed to minimize this issue, it can still play a factor in the long-term durability of the equipment [25,26,27,28]. The fuel cell also requires maintenance. Air filters need to be replaced periodically to prevent dust and other particles from contaminating the system and degrading performance [165,166]. Also, the fuel cell can be poisoned by impurities in the hydrogen gas [165,167].
Economic issues	An all-in-one hydrogen home that produces its own electricity and hydrogen can be very costly due to several factors, primarily related to the high price of the specialized equipment and the complexity of integrating the entire system [59,168]. Unlike mature technologies like solar panels, the market for residential-scale hydrogen systems is still in its infancy, which means prices are high and supply chains are not yet optimized for mass production. The initial cost of buying and installing the equipment (i.e., CAPEX) can be a big financial burden to the homeowner. The electrolyzer is the most expensive component, with residential-scale electrolyzers ranging from several thousand to tens of thousands of dollars, depending on the technology and capacity [169]. The fuel cell is another major expense, with residential fuel cells typically ranging from several thousand dollars for a smaller unit, up to US$ 20,000 for a larger system capable of powering a whole home [170,171]. Moreover, hydrogen storage introduces additional costs. A small-scale, high-pressure tank for a home can cost several thousand dollars, which can vary depending on volume and pressure rating. Specifically, the U.S. Department of Energy suggests a target cost of US$ 333 per kg of stored hydrogen, though this is for a high-volume, industrialized production scenario [172].
Technology maturity issues	The biggest reason for the high costs of such a system is that the industry for residential hydrogen is not yet a mature market. Components are not mass produced but rather in small batches based on demand, which prevents manufacturers from benefiting from economies of scale. Consequently, there are few companies currently selling residential hydrogen systems, resulting in limited competition and high prices.

. Overall, the reliance on renewable resources for the generation of hydrogen and the intermittency issues that arise from the renewable resources is a major drawback. It will ultimately affect the lifetime of the equipment, hinder the energy autonomy of the home by limiting hydrogen production, and ultimately mean that the home has to be connected to the electricity grid to avoid downtime.

In the long term, if plans for a fully integrated hydrogen economy are realized [173,174,175,176], the direct connection of the hydrogen grid to a home will alleviate all maintenance and cost issues, as summarized in

Table 2. Comparison of an all-in-one hydrogen home, a home connected to a hydrogen grid and a home with an on-site hydrogen storage system.

Feature	All-in-One Home	Home on a Hydrogen Grid	On-Site Hydrogen Storage Home
On-site Hydrogen Production	Yes	No	No
On-site Hydrogen Storage	Yes	No	Yes
On-site Need for Renewables	Yes	No	No
On-site Electricity Storage	Yes	No	No
Fuel Cell	Yes	Yes	Yes
Maintenance Burden	High	Low to Moderate	Low
Complexity of System	Very High	Low	Very Low
Chance of Supply Interruptions	High	Low	Very Low

. The maintenance and safety aspects of the hydrogen grid would fall to the utility company, and due to economies of scale, the hydrogen price will decrease, reducing overall costs for the homeowner even further. However, the autonomy of the home is diminished; interruptions in hydrogen supply will affect the electricity production. In addition, if appliances run on hydrogen, this will add more maintenance burden, complexity and cost to the homeowner as these appliances are not currently mass-produced and the technical knowledge around them is not established.

4. Mathematical Modeling for Off-Grid Autonomous Home with On-Site Hydrogen Storage

An autonomous home that is physically disconnected from the electricity utility infrastructure, equipped with on-site hydrogen storage, offers a resilient solution for energy autonomy and off-grid living. Instead of relying on an all-in-one hydrogen system, this approach uses externally delivered hydrogen stored on-site, which is then used on-demand to generate electricity through a fuel cell. This configuration enables reliable backup power and supports decentralized energy supply, with the potential for renewable electricity generation as part of the broader system, though not for hydrogen production itself. Consistent with recent voltage-power self-coordinated control schemes for storage and distributed generation inverters, the off-grid hydrogen powered home is treated as an autonomous micro-grid whose reliability depends on advanced load side inverter power conditioning [177]. It is important to note that, to evaluate the techno-economic feasibility of the autonomous residence with high granularity, this study adopts a “gate-to-use” system boundary. As illustrated in Figure 6, the modeling framework begins at the household hydrogen storage interface. Logistics, delivery frequency, and any additional fees associated with serving remote homes are captured implicitly through the wide hydrogen price range adopted in Table 3, whereas explicit modeling of the upstream supply chain remains outside the optimization boundary of this study.

The core of the system remains the fuel cell, which converts stored hydrogen into electricity as needed. Additionally, integrating a waste heat capture system or combined heat and power (CHP) unit with the fuel cell allows the recovery of heat for domestic hot water and central heating, enhancing overall efficiency and minimizing energy waste. In this work, the household’s total energy demand is modeled to be met directly from the hydrogen-based system, ensuring a focus on the performance and feasibility of hydrogen as the primary energy carrier.

The household comprises various integrated components, as seen in Figure 6. Primary and standby fuel cells, such as dual PEM fuel cell modules, are sized for reliable power delivery with redundancy. The selection of a dual fuel cell module (primary and standby units) follows the principles of modular redundancy common in critical off-grid infrastructure, in addition to achieving a higher availability factor both in terms of possible failures and maintaining critical residential loads [178,179,180]. Moreover, by utilizing a smaller standby unit, the system ensures that the active stack operates closer to its peak efficiency point [180,181]. Lastly, any potential downtime for stack maintenance is mitigated by the presence of the standby fuel cell, which can maintain critical residential loads while the primary system is serviced, thereby ensuring a high system availability (>98%) over a 20-year project life. Future iterations of this model could further enhance this predictive reliability by incorporating advanced voltage model parameter identification methods. As noted in the recent literature [182], adopting high-precision estimation techniques for electrochemical variables represents a key step toward more accurately capturing efficiency fluctuations and degradation effects under dynamic residential demand.

Also, the household includes hydrogen storage, providing multi-day storage to bridge seasonal variations. In addition, a power conditioning system is present for voltage regulation, and a small UPS battery for transient response and brief outages during fuel cell transitions. Safety and controls for hydrogen leak detection, emergency shutdown, pressure relief and the energy management system are also present. The system operates as a closed-loop energy conversion pathway as stored hydrogen is fed continuously to the primary fuel cell at regulated pressure, generating DC electricity via electrochemical conversion to supply standard DC household loads. When primary fuel cell output cannot fully meet load demand (e.g., during transient load spikes), the standby fuel cell activates.

Table 3. Technical and economic data and assumptions.

Parameter	Unit	Value	Ref.
Technical parameters
Base year	year	2026	–
Fuel cell efficiency, ${\eta }_{\mathrm{FC}}$	%	55	[181]
Hydrogen lower heating value, ${\mathrm{LHV}}_{{\mathrm{H}}_2}$	kWh/kg	33.33	–
Peak load margin, $k_{\mathrm{margin}}$	%	125	–
Stand-by capacity ratio, $\beta$	%	50	–
Fuel cell replacement interval	years	15	–
UPS battery replacement interval	years	10	–
Hydrogen storage capacity	days	7	–
UPS battery back-up	minutes	15	–
System lifetime	years	20	–
Economic parameters
Primary fuel cell cost, $C_{\mathrm{FC},\mathrm{primary}}$	US$/kW	400	[183,184]
Stand-by fuel cell cost multiplier	%	80	[183,184]
Fuel cell BOP cost	US$/kW	600	[185]
Fuel cell installation cost	US$/kW	150	[186,187]
Annual fuel cell maintenance cost	US$/kW	45	[186]
Fuel cell replacement cost ratio	–	0.6	[186]
Inverter cost	US$/kW	180	[15,188]
Power electronics cost	US$/kW	120	[186]
Control system cost	US$	8000	[15,189,190]
Safety system cost	US$	4000	[15,186]
Hydrogen storage cost	US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$	800	[191]
UPS system cost	US$/kW	200	[192]
UPS battery cost	US$/kWh	400	[192]
Insurance rate	% of CAPEX	1	–
Hydrogen price	US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$	2–12	[63,193,194,195,196,197]
Grid electricity price	US$/kWh	0.1–1	[198,199]

Table 3. Technical and economic data and assumptions.

Parameter	Unit	Value	Ref.
Technical parameters
Base year	year	2026	–
Fuel cell efficiency, ${\eta }_{\mathrm{FC}}$	%	55	[181]
Hydrogen lower heating value, ${\mathrm{LHV}}_{{\mathrm{H}}_2}$	kWh/kg	33.33	–
Peak load margin, $k_{\mathrm{margin}}$	%	125	–
Stand-by capacity ratio, $\beta$	%	50	–
Fuel cell replacement interval	years	15	–
UPS battery replacement interval	years	10	–
Hydrogen storage capacity	days	7	–
UPS battery back-up	minutes	15	–
System lifetime	years	20	–
Economic parameters
Primary fuel cell cost, $C_{\mathrm{FC},\mathrm{primary}}$	US$/kW	400	[183,184]
Stand-by fuel cell cost multiplier	%	80	[183,184]
Fuel cell BOP cost	US$/kW	600	[185]
Fuel cell installation cost	US$/kW	150	[186,187]
Annual fuel cell maintenance cost	US$/kW	45	[186]
Fuel cell replacement cost ratio	–	0.6	[186]
Inverter cost	US$/kW	180	[15,188]
Power electronics cost	US$/kW	120	[186]
Control system cost	US$	8000	[15,189,190]
Safety system cost	US$	4000	[15,186]
Hydrogen storage cost	US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$	800	[191]
UPS system cost	US$/kW	200	[192]
UPS battery cost	US$/kWh	400	[192]
Insurance rate	% of CAPEX	1	–
Hydrogen price	US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$	2–12	[63,193,194,195,196,197]
Grid electricity price	US$/kWh	0.1–1	[198,199]

The system sizing and techno-economic performance are obtained by solving a deterministic optimization problem that minimizes the total discounted lifecycle cost of the autonomous hydrogen home over the project lifetime of 20 years. The objective function is the net present value of all capital and operating expenditures:

$$\underset{\mathbf{x}}{min}J\left(\mathbf{x}\right)=\sum _{y=1}^{20}\left\{{\displaystyle \frac{{\mathrm{CAPEX}}_y\left(\mathbf{x}\right)+{\mathrm{OPEX}}_y\left(\mathbf{x}\right)}{{(1+r)}^y}}\right\},$$

(1)

where r is the discount rate; ${\mathrm{CAPEX}}_y$ includes the initial investment and scheduled replacements of the fuel cell stacks, batteries and hydrogen storage; and ${\mathrm{OPEX}}_y$ includes hydrogen fuel costs, maintenance and insurance. The decision variables $\mathbf{x}$ define the main design parameters of the home energy system, such as $P_{\mathrm{FC},\mathrm{primary}}$, $P_{\mathrm{FC},\mathrm{standby}}$, $P_{\mathrm{bat}}$, and $S{C}_{{\mathrm{H}}_2}$. These variables are constrained by technical, reliability and autonomy requirements as described below.

The instantaneous energy balance for the residential load on an hourly basis is given by

$$P_{\mathrm{load}}\left(t\right)=P_{\mathrm{FC},\mathrm{primary}}\left(t\right)+P_{\mathrm{FC},\mathrm{standby}}\left(t\right)+P_{\mathrm{bat}}\left(t\right),$$

(2)

where $P_{\mathrm{load}}\left(t\right)$ is the residential load power at time t in kW, $P_{\mathrm{FC},\mathrm{primary}}\left(t\right)$ is the primary fuel cell output power in kW, $P_{\mathrm{FC},\mathrm{standby}}\left(t\right)$ is the standby fuel cell output power in kW (normally zero), and $P_{\mathrm{bat}}\left(t\right)$ is the auxiliary battery output power in kW, for brief transients only.

The hydrogen mass flow rate ${\dot{m}}_{{\mathrm{H}}_2}\left(t\right)$ in kg/h, required to generate electrical power $P_{\mathrm{FC}}$ in kW, from a fuel cell system with electrical efficiency ${\eta }_{\mathrm{FC}}$ is

$${\dot{m}}_{{\mathrm{H}}_2}\left(t\right)={\displaystyle \frac{P_{\mathrm{FC}}\left(t\right)}{{\eta }_{\mathrm{FC}}·{\mathrm{LHV}}_{{\mathrm{H}}_2}}},$$

(3)

where ${\mathrm{LHV}}_{{\mathrm{H}}_2}=33.33$ kWh/kg is the lower heating value of hydrogen gas. For PEM fuel cells operating at rated conditions, electrical efficiency ${\eta }_{\mathrm{FC}}=0.55$ is typical for current commercial units, yielding a hydrogen consumption ratio of 0.0545 kg/kWh.

The primary fuel cell capacity $P_{\mathrm{FC},\mathrm{primary}}$ is sized to meet peak residential load with a safety margin for reliability:

$$P_{\mathrm{FC},\mathrm{primary}}=P_{\mathrm{peak}}\times k_{\mathrm{margin}},$$

(4)

where $P_{\mathrm{peak}}$ is the maximum instantaneous household load in kW and $k_{\mathrm{margin}}=1.25$ represents a 25% design margin to ensure the fuel cell can reliably meet peak demand without operating at absolute maximum output, which reduces efficiency and accelerates degradation. A standby fuel cell system provides redundancy and reliability:

$$P_{\mathrm{FC},\mathrm{standby}}=P_{\mathrm{FC},\mathrm{primary}}\times \beta ,$$

(5)

where $\beta =0.5$ represents a standby capacity ratio, meaning the standby system is sized at 50% of the primary system. This configuration provides sufficient redundancy to maintain household loads if the primary fuel cell requires maintenance, experiences temporary failure or during extreme peak transient periods.

Hydrogen storage must be sized to provide multi-day autonomy. For off-grid homes relying on external hydrogen supply, storage capacity ${\mathrm{SC}}_{{\mathrm{H}}_2}$ in kg is determined by practical delivery frequency and emergency reserve requirements:

$${\mathrm{SC}}_{{\mathrm{H}}_2}={\mathrm{DC}}_{{\mathrm{H}}_2}\times N_{\mathrm{days}},$$

(6)

where ${\mathrm{DC}}_{{\mathrm{H}}_2}$ is the hydrogen daily consumption in kg/day, and N represents number of days required for autonomy, ensuring the home can operate for a specified period without hydrogen delivery.

The total capital cost CAPEX in US$ of an off-grid autonomous hydrogen home system comprises multiple components given below:

$$\mathrm{CAPEX}=C_{\mathrm{FC},\mathrm{primary}}+C_{\mathrm{FC},\mathrm{standby}}+C_{\mathrm{power}}+C_{\mathrm{safety}}+C_{{\mathrm{H}}_2\mathrm{storage}}+C_{\mathrm{UPS}},$$

(7)

where $C_{\mathrm{FC},\mathrm{primary}}$ is the capital cost of the primary fuel cell stack, $C_{\mathrm{FC},\mathrm{standby}}$ is the capital cost of standby fuel cell stack, $C_{\mathrm{power}}$ is the capital cost of the power conditioning and control system, $C_{\mathrm{safety}}$ is the capital cost of the safety system (H₂ detection, emergency shutdown), $C_{{\mathrm{H}}_2\mathrm{storage}}$ is the capital cost of hydrogen storage tanks, and $C_{\mathrm{UPS}}$ is capital cost of the UPS battery.

The annual operating costs ${\mathrm{OPEX}}_y$ in US$ comprise the annual cost of fuel $C_{\mathrm{fuel}}$, maintenance cost $C_{\mathrm{maintenance}}$, insurance cost $C_{\mathrm{insurance}}$, and periodic component replacement $C_{\mathrm{replacement}}$:

$${\mathrm{OPEX}}_y=C_{\mathrm{fuel}}+C_{\mathrm{maintenance}}+C_{\mathrm{insurance}}+C_{\mathrm{replacement}}.$$

(8)

The levelized cost of electricity (LCOE) expresses the average cost per unit of electrical energy delivered over the system lifetime as

$$\mathrm{LCOE}=\left\{{\displaystyle \frac{{\sum }_{y=1}^{20}\left[\frac{{CAPEX}_y+{OPEX}_y}{{(1+r)}^y}\right]}{{\sum }_{y=1}^{20}\left[\frac{E_y}{{(1+r)}^y}\right]}}\right\},$$

(9)

where $E_y$ is the annual electrical energy supplied to the residence in kWh and r is the discount rate.

For the calculation of the payback period PBP in years, for off-grid systems without grid connection to provide cost avoidance benchmarking, a hypothetical alternative cost is calculated based on assumed grid electricity rates $P_{\mathrm{grid}}$ in US$/kWh:

$$\mathrm{PBP}={\displaystyle \frac{\mathrm{CAPEX}}{E_y\times P_{\mathrm{grid}}-{\mathrm{OPEX}}_y}}.$$

(10)

The above mathematical expressions and system design for an off-grid fully autonomous home with an on-site hydrogen storage system are modeled based on a comprehensive MATLAB R2024b program engineered to optimize hydrogen fuel cell systems in residential applications. The overall program logic, structured in a sequential workflow, is visualized in Figure 7. The computational framework begins with user-defined input parameters spanning hydrogen pricing, fuel cell efficiency, energy density, and component capital and operational costs. From these parameters, the program systematically generates detailed hourly appliance load profiles, encompassing a diverse range of residential equipment, including heating, cooling, cooking, and domestic hot water systems with seasonal variability built into consumption patterns.

These load profiles serve as the foundation for dimensioning both the primary fuel cell stack and a redundant standby unit, ensuring adequate capacity to meet peak demand while maintaining operational margin. The sizing algorithm simultaneously determines the hydrogen storage volume required to sustain system autonomy over a user-specified duration and calculates the battery backup capacity necessary for transient power support during fuel cell transitions. The program then executes comprehensive hydrogen consumption calculations, converting hourly electricity demand into corresponding hydrogen mass requirements based on fuel cell electrical efficiency and hydrogen lower heating value, while simultaneously computing the operational cost of hydrogen supply on an hourly and annual basis.

Beyond energy calculations, the tool performs a complete techno-economic evaluation encompassing CAPEX analysis, with detailed cost itemization for fuel cell stacks, balance of plant components, power electronics, hydrogen storage infrastructure, and safety systems and comprehensive OPEX accounting for fuel costs, maintenance, insurance, and component replacement schedules. The program calculates lifecycle cost metrics, including net present value of operating costs over the system design lifetime, total lifecycle cost, and levelized cost of electricity, alongside key financial indicators such as simple payback period and comparative cost analysis against grid electricity. In parallel, a reliability assessment module quantifies system availability through probabilistic analysis of the redundant fuel cell configuration, determining combined availability and corresponding expected annual downtime hours.

5. Results and Discussion

The technical and economic data and assumptions employed in the model are presented in Table 3. The model operates within a base year of 2026, establishing the reference timeframe for all economic calculations and technology cost projections. Fuel cell electrical efficiency is set at 55%, representing the current state of the art for PEM fuel cells operating under typical residential load conditions.

The lower heating value of hydrogen is specified at 33.33 kWh/kg, which represents the chemical energy content available for conversion to electricity. The peak load margin coefficient of 125% ensures that the primary fuel cell is sized with adequate capacity to handle instantaneous peak demands while maintaining operational stability and avoiding excessive transient stress. The standby capacity ratio of 50% defines the redundant fuel cell system as half the primary capacity, providing fault tolerance and ensuring system reliability during primary unit maintenance or failure. Fuel cell stack replacement is scheduled at 15-year intervals, reflecting degradation patterns and end-of-life characteristics of PEM fuel cell technology, while battery systems are replaced every 10 years due to more rapid electrochemical degradation. The hydrogen storage capacity is dimensioned for 7 days of autonomy, balancing the competing demands of system resilience against off-grid supply interruptions and the capital cost of large storage volumes. UPS battery backup is set to 15 min, providing sufficient time for controlled fuel cell startup and load transfer during transient events. The overall system design lifetime is 20 years, a standard assumption for residential energy infrastructure reflecting typical mortgage terms and technology lifecycle expectations.

Fuel cell capital costs are segmented into multiple components. The primary fuel cell stack cost is set at 400 US$/kW, representing the cost of the electrochemical conversion module [183,184]. The standby fuel cell cost multiplier of 80% reflects lower procurement costs when acquiring redundant units simultaneously with primary systems. The balance of plant (BOP) cost of 600 US$/kW encompasses auxiliary equipment, including hydrogen supply regulation, water management, thermal management systems, and control electronics necessary for complete fuel cell operation [185]. Installation labor and integration costs are estimated at 150 US$/kW [186,187]. Annual fuel cell maintenance, set at 45 US$/kW, accounts for scheduled inspections, hydrogen purity monitoring, component wear management, and corrective maintenance [186]. The fuel cell replacement cost ratio of 0.6 indicates that replacement stack costs are estimated at 60% of the original capital cost, reflecting manufacturing experience curves and technological maturation [186].

Power electronics costs include inverters at 180 US$/kW for power control and general power conditioning at 120 US$/kW [15,186,188]. Fixed control system infrastructure is valued at US$ 8000 and encompasses supervisory control logic, energy management algorithms, and system monitoring capabilities [15,189,190]. Safety systems are budgeted at US$ 4000, covering pressure relief, fire suppression, hydrogen leak detection, and emergency shutdown mechanisms required for residential hydrogen systems [15,186]. Hydrogen storage infrastructure is costed at 800 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ capacity, covering storage tanks and safety-rated storage vessel fabrication [191]. Uninterruptible power supply (UPS) systems are specified at 200 US$/kW, providing short-term power bridging during transients. Battery backup systems are costed at 400 US$/kWh, supporting the 15 min autonomy requirement during fuel cell transitions [192]. Insurance costs are estimated at 1% of total capital expenditure annually, covering liability, property damage, and equipment coverage for the residential hydrogen system.

To examine parametrically the effect of hydrogen and grid electricity prices on system economics, specific price ranges were selected to reflect real market statistics and regional variations. Hydrogen pricing varies significantly depending on the production technology and feedstock. Based on current production pathways, the cost of hydrogen ranges from 0.8 to 5 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ for natural gas-produced hydrogen (with carbon capture and storage), 1.8–4.6 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ for coal-produced hydrogen (with carbon capture and storage), and from 3.8 up to more than 12 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ for renewable source-produced hydrogen [193]. Gray hydrogen, produced from natural gas without carbon capture, remains the most cost-competitive option and represents the lower end of the price spectrum. The inclusion of the lower price bracket (2–4 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$) is further supported by international policy targets aimed at achieving cost parity with fossil fuels. For instance, the U.S. Hydrogen Energy Earthshot targets a production cost of 1 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ by 2031 [194,195], while the European Hydrogen Bank auctions suggest a rapid downward trend in subsidized green hydrogen prices [196,197]. Furthermore, the IEA Global Hydrogen Review 2025 indicates that as global electrolyzer capacity expands from MW to GW scales, the levelized cost of renewable hydrogen is projected to fall below 3 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ in high-resource regions by 2030 [193]. Therefore, in order to establish a comprehensive parametric analysis, six distinct hydrogen price scenarios were evaluated at 2 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ intervals, ranging from 2 to 12 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$.

Grid electricity pricing serves as the critical benchmark for economic comparison between the off-grid autonomous hydrogen home with on-site storage and conventional grid-connected residential systems. Grid electricity prices exhibit substantial geographical variation. Within the European Union, the average electricity price for the second half of 2024, inclusive of taxes, was approximately 0.29 €/kWh (equivalent to 0.34 US$/kWh), with regional variation ranging from a minimum of 0.10 €/kWh (0.12 US$/kWh) to a maximum of 0.40 €/kWh (0.46 US$/kWh) [198]. Similarly, in the United States, electricity prices vary considerably by state, with Hawaii recording the highest price at 0.39 US$/kWh in 2023 and Utah the lowest at 0.09 US$/kWh, while the national average stands at approximately 0.13 US$/kWh [199]. To capture this diverse pricing environment and enable robust sensitivity analysis, a grid electricity price range of 0.1 to 1 US$/kWh was evaluated, encompassing both current low-cost regions and potential future price escalation scenarios. This parametric approach allows the economic viability of the hydrogen-based autonomous home system to be assessed across multiple markets and price evolution pathways, providing insights into the sensitivity of system economics to key market variables and technological parameters.

Figure 8 illustrates a typical electricity demand profile of the modeled autonomous hydrogen house and highlights the seasonal variability of residential loads. Peak monthly consumption of approximately 1300 kWh occurs in the summer months (June–September), driven predominantly by air conditioning demand, whereas consumption falls to about 1050–1100 kWh during the spring and autumn transition periods and remains elevated at roughly 1175–1180 kWh in January and December due to space heating requirements. Appliances such as the refrigerator, induction cooktop and water heater constitute a relatively stable baseload throughout the year, while the air conditioner and space heater introduce pronounced seasonality that directly translates into the temporal pattern of hydrogen consumption.

The interaction between the residential load and the fuel cell system sizing is illustrated in Figure 9, which compares the hourly or representative monthly peak loads with the installed primary PEM fuel cell capacity. The primary fuel cell is calculated at approximately 13.18 kW, corresponding to a sizing margin of 125% relative to the peak electrical demand of about 10.5 kW, ensuring that the unit does not routinely operate at its maximum rated output, thereby mitigating performance degradation and extending stack lifetime. In combination with a 50% standby unit (6.59 kW), this configuration achieves a modeled system availability of 99.85%, with an expected annual downtime of 13.1 h, which is appropriate for residential autonomous applications while avoiding excessive overdimensioning of generation capacity.

The resulting monthly hydrogen demand profile is presented in Figure 10. Hydrogen consumption peaks at 70.50 ${\mathrm{kg}}_{{\mathrm{H}}_2}$/month in July and August, decreases to about 57.56 ${\mathrm{kg}}_{{\mathrm{H}}_2}$/month in April and November, and remains relatively high at 64.20 ${\mathrm{kg}}_{{\mathrm{H}}_2}$/month in January and December, yielding an annual variation in the order of 12.88 ${\mathrm{kg}}_{{\mathrm{H}}_2}$. This moderate seasonal spread indicates that storage sizing is primarily governed by multi-day autonomy rather than seasonal shifting, and the adopted 7-day storage capacity provides sufficient resilience against short-term delivery disruptions without incurring the very high capital cost associated with large seasonal storage required in fully renewable-driven systems.

The estimated system CAPEX and OPEX (excluding hydrogen cost) are illustrated in

Table 4. System CAPEX breakdown.

System Component	Cost (US$)	Share (%)
Primary FC system	15,153	22.73
Control and safety	12,000	21.96
Hydrogen storage	11,618	21.26
Standby FC system	6259	11.45
Power electronics	5930	10.85
UPS and battery	3690	6.75
Total	54,649	100

and

Table 5. System annual OPEX excluding hydrogen cost.

System Cost	Cost (US$)	Share (%)
Maintenance	741	43.9
Insurance	546	32.37
Stack replacement	295	17.48
Battery replacement	106	6.24
Total	1688	100

. The calculated techno-economic implications of hydrogen price variation are summarized in

Table 6. Hydrogen annual cost and LCOE for different hydrogen prices.

Hydrogen Price (US$/${\mathbf{kg}}_{{\mathbf{H}}_{\mathbf{2}}}$)	Hydrogen Annual Cost (US$)	LCOE (US$/kWh)
2	1514	0.3292
4	3029	0.3917
6	4543	0.4543
8	6058	0.5169
10	7572	0.5794
12	9087	0.6420

, which reports the annual hydrogen cost and corresponding LCOE for hydrogen prices between 2 and 12 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$. As expected, the annual fuel cost increases linearly from 1514 US$ at 2 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ to about 9087 US$ at 12 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$, while the LCOE rises from approximately 0.3292 to 0.6420 US$/kWh, with all other operating cost components remaining constant. These values are substantially higher than typical grid-supplied electricity and utility-scale renewable generation costs.

However, it should be noted that this assessment assumes static equipment costs over the project duration. In a 20-year lifecycle context, the “learning curve effect” is expected to significantly drive down the CAPEX of core components such as fuel cell stacks and hydrogen storage. As these technologies reach greater industrial maturity and benefit from economies of scale, projected cost reductions and increased investment could fundamentally alter the long-term LCOE [193,200,201]. Consequently, while current figures reflect a premium over grid electricity, the forward-looking economic viability is likely to improve as the capital intensity of the system diminishes over time.

The influence of both hydrogen and grid electricity prices on the investment attractiveness of the autonomous hydrogen house is further elucidated by the payback analysis in Figure 11. For each hydrogen price scenario, there exists a critical grid tariff below which simple payback periods become prohibitively long (approaching or exceeding the system lifetime), reflecting insufficient annual cost savings to offset capital and operating expenditures. At the upper hydrogen cost of 12 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$, grid tariffs above roughly 0.9 US$/kWh are required to reduce the payback period below 40 years, whereas at 2 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$, payback times of less than 20 years can be achieved once grid prices exceed approximately 0.42 US$/kWh. Under representative EU electricity grid retail conditions (about 0.34 US$/kWh), the most favorable hydrogen price considered (2 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$) yields a payback period in the order of 35 years, indicating that under current market conditions the system is primarily justified in high-tariff or strongly resilience-driven contexts rather than purely on cost grounds.

Placing these results in the broader context of hydrogen-based residential supply options, the off-grid autonomous hydrogen house with on-site storage occupies an intermediate position between grid-connected hydrogen homes and all-in-one hydrogen homes with on-site renewable energy production. In an off-grid autonomous house with on-site hydrogen storage, the absence of an on-site electrolyzer and renewable generation dedicated to hydrogen production substantially reduces system complexity and maintenance requirements compared to all-in-one designs, while multi-day hydrogen storage and redundant fuel cell capacity preserve a high degree of energy autonomy and operational reliability. Grid-connected hydrogen homes, by contrast, sacrifice full autonomy but benefit from reduced generation and storage capacities, allowing the grid to cover residual load and seasonal variability, which generally leads to lower LCOE and shorter payback periods, particularly in markets with moderate tariffs. Fully renewable-driven hydrogen homes with on-site electrolyzers can, in principle, achieve the highest degree of self-sufficiency and seasonal balancing, but they incur very high capital costs, complex operation due to intermittent electrolyzer cycling, and elevated maintenance burdens, often necessitating retaining a grid connection in climates with significant seasonal irradiance variability.

Within this spectrum, the modeled off-grid autonomous hydrogen house with on-site hydrogen storage emerges as a technically robust and simpler solution for remote, island or high-tariff regions, provided that low-carbon hydrogen can be supplied at competitive prices (below about 3–4 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$) and that non-economic drivers such as energy security, resilience to grid outages and deep decarbonization objectives are adequately valued by decision makers.

6. Conclusions

This comprehensive mathematical modeling and economic analysis has developed a rigorous framework for evaluating autonomous hydrogen homes designed for complete off-grid operation with on-site hydrogen storage. The study presents detailed techno-economic findings that characterize the viability of such systems across diverse market and geographic contexts. For most residential applications, a home with on-site hydrogen storage represents a far more practical and consumer-friendly approach than fully integrated all-in-one systems as it offloads the most complex and maintenance-intensive components, namely, electrolyzer operation and associated control systems, to centralized production and distribution infrastructure. This configuration reduces operational complexity and mitigates the technical risks associated with intermittent renewable energy cycling on sensitive electrochemical equipment.

The technical analysis confirms that off-grid autonomous hydrogen homes employing dual Proton Exchange Membrane fuel cell systems with multi-day gas storage can reliably supply residential power year-round, achieving system availability of 99.85% with a manageable downtime of only 13.1 h annually. The redundant fuel cell architecture, incorporating a primary unit sized to meet peak residential demand with a 25% design margin and a standby unit at 50% capacity, provides robust fault tolerance and allows for preventive maintenance without loss of household power. This reliability performance demonstrates that the technology is mature enough for pilot deployment in appropriately selected applications, particularly where energy security and resilience take priority over minimizing upfront capital cost.

From an economic perspective, however, current market conditions present significant challenges to widespread adoption of autonomous hydrogen homes for general residential use. Sensitivity analysis demonstrates critical dependence of system economics on hydrogen pricing. At hydrogen costs below 3.00 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$, representative of mature green hydrogen production with economies of scale, competitive payback periods of 12 to 15 years become achievable in high-cost electricity regions with tariffs exceeding 0.40 US$/kWh. Conversely, at higher hydrogen prices of 6 to 12 US$/${\mathrm{kg}}_{{\mathrm{H}}_2}$ reflecting current immature supply chains, payback periods extend beyond 40 years even in the most favorable tariff environments. This strong hydrogen price sensitivity underscores that near-term deployment of off-grid autonomous hydrogen homes should be concentrated in regions where hydrogen supply infrastructure is already developing or where high grid electricity costs offset the current hydrogen cost premium. Realizing the full potential of off-grid autonomous hydrogen homes requires coordinated technology advancement across multiple domains: hydrogen production cost reduction through scale-up of electrolysis and renewable energy generation, storage technology development targeting both cost and performance improvements, standardization of residential fuel cell systems for manufacturing economies, and development of regulatory frameworks and incentive structures that properly value resilience and decarbonization.