Seasonal gas-saving potential of off-grid PV-to-heat systems in Hungary

As global energy demand increases, improving the sustainability and efficiency of energy use becomes a pressing challenge. Solar-based technologies offer significant potential for decentralized energy production due to their modularity and growing availability. This study focuses on the integration of household-scale off-grid photovoltaic (PV) systems with electric thermal storage to reduce residential natural gas consumption—particularly for space heating and domestic hot water production—in the context of Hungary. The research first explored whether average monthly household natural gas consumption can be estimated using publicly available statistical data. Based on the findings, a seasonal consumption profile was constructed for Hungary, enabling the modeling of a 3.2 kWp off-grid PV system combined with a 200-liter water tank equipped with a 2.4 kW heating element. The simulated system was found to generate approximately 3800 kWh of electricity annually, corresponding to a potential amount of nearly 393 m³ of natural gas saved per household. The simulation was conducted on a monthly basis, reflecting the resolution of available consumption data, as more detailed temporal datasets are not publicly accessible. The novelty of the study lies in its application of off-grid PV systems explicitly designed for thermal energy generation, a topic that has received limited attention in the literature, while also developing a data-driven, reproducible national-scale framework that estimates the seasonal gas-saving potential of such PV-to-heat systems based on official statistical data, thereby bridging the gap between high-resolution case studies and aggregated energy policy models. In addition to quantifying natural gas savings, the study emphasizes the problem of seasonal surplus energy and underlines the importance of proper sizing and utilization strategies for off-grid systems. The modeling framework can be adapted to other countries where similar data are available. • This study outlines a data-based framework to assess household gas savings from off-grid PV-to-heat systems in Hungary. • A 3.2 kWp off-grid PV-to-heat system with 200 L storage can cut household gas use by 26 % annually. • The modeled configuration produces ≈ 3800 kWh per year, replacing about 393 m³ of natural gas. • Seasonal imbalance causes ≈ 36 % loss of potential, mainly due to summer PV surplus. • The proposed monthly-scale approach is transparent and transferable to other EU countries.