Replacing gas boilers with heat pumps is the fastest way to cut German gas consumption

The Russo-Ukrainian War has severely disrupted fossil gas supply security, creating urgency for long-term contract decisions that threaten the Paris Climate Agreement. This research investigates the potential of renewable electricity and heat pumps to mitigate this risk and contribute to decarbonization. The heating sector, a major greenhouse gas emitter, can be decarbonized through building improvements, solar thermal, and heat pump adoption. While renewable hydrogen is unsuitable for domestic heating due to cost and efficiency issues, heat pumps present a viable alternative. This study hypothesizes that installing heat pumps is one of the fastest ways to reduce gas consumption, given their modularity and relatively simple installation process. However, heat pumps compete with other electricity demands and may rely on gas-fired power plants during periods of insufficient renewable energy. The study uses Germany, with its significant reliance on natural gas for heating, as a case study to model hourly gas consumption in buildings, industry, and electricity generation. The methodology, however, has broader applicability to other temperate climates.

The literature review highlights the necessity of rapid de-fossilisation for limiting global temperature increase. Cost-effective decarbonization of the electricity sector involves replacing fossil fuels with renewables like photovoltaics (PV) and wind power. The literature emphasizes the role of heat pumps, powered by renewable electricity, as a crucial component in decarbonizing heating. Other approaches such as conscious consumer behavior, district heating networks utilizing industrial waste heat and geothermal energy, and various storage technologies are also mentioned. The authors note limitations of unsustainable biomass expansion and the unsuitability of renewable hydrogen for domestic heating due to economic factors. Integrated assessment models show a wider range of development pathways for heat generation compared to electricity.

The study employs a bottom-up modelling approach using hourly resolution data for Germany. Data sources include statistics on gas consumption for space heating and cooking in private households and industrial sectors (chemical, paper, food processing). Hourly load curves for industrial sectors and heat pumps are integrated, considering variations based on temperature and day type. Electricity system modelling utilizes hourly generation data for power plants, renewables (wind, PV), and storage capacities. The model prioritizes maximum fossil gas replacement with renewable electricity. A key factor is the coefficient of performance (COP) of heat pumps, which is compared to gas-fired power plant efficiency. The model incorporates hourly COP values based on building energy class (insulation status), water temperature requirements of heating circuits, and the performance of commercially available air-to-water heat pumps. Qualitative interviews with plumbing and heating company owners inform scenario development, addressing constraints like labor shortages, training needs, and technical challenges in integrating heat pumps into existing systems. Four scenarios are modeled: 'Installers' roadmap', 'Assumption scenario', 'Fast scenario', and 'Very fast scenario'. These scenarios consider varying levels of heat pump installations and associated government incentives and training initiatives. The model also accounts for the annual efficiency of combined cycle gas turbines (CCGTs) in electricity generation. Mathematical procedures are described, detailing calculations of gas consumption and substitution, including gas consumption variation based on temperature and scenarios for heat pump installations.

The model demonstrates the significant potential of heat pump installation to reduce fossil gas consumption in Germany. In the 'very fast scenario,' which assumes concerted efforts in government support, industry cooperation, and public engagement, approximately 60% of Russian gas imports could be replaced by 2025. This translates to a 30% reduction in overall gas consumption by 2025 and at least 180 Mt of greenhouse gas emissions savings. The model shows that in the initial years, additional wind and PV capacity primarily reduces the load hours of gas-fired power plants. From 2024, heat pumps draw substantial renewable electricity. The sensitivity analysis, considering year-to-year weather variations, shows relatively small impacts on gas savings. The results suggest that accelerated heat pump adoption, even with existing radiator systems and partial fossil-fuel electricity generation, is a highly effective strategy for reducing reliance on fossil gas. The study emphasizes that success depends on government incentives, installer training, and grid expansion. The scenarios outline the potential range of gas substitution depending on the level of investment and effort in heat pump deployment.

The findings confirm the hypothesis that heat pump installation is a rapid and effective strategy to reduce gas consumption in Germany. The success of the 'very fast scenario' highlights the importance of targeted policy interventions, addressing both technological and socio-economic factors. The study's hourly resolution modelling provides detailed insights into the dynamic interaction between renewable electricity generation, heat pump operation, and gas-fired power plant load hours. The limitations of the model are acknowledged, and strategies for overcoming them are outlined. The results are relevant for energy policymakers seeking strategies to enhance energy security and achieve climate goals. The study's methodology could be adapted to other countries with similar heating systems and renewable energy potential. This work offers a valuable contribution to the ongoing discussions about energy transition pathways in the face of geopolitical instability.

This study demonstrates that accelerated heat pump deployment is a viable and effective strategy to significantly reduce fossil gas consumption, enhancing energy security and contributing to climate goals. The success of this strategy hinges on concerted efforts involving government support, industry cooperation, and public engagement. Future research could focus on further refining the model to incorporate more detailed grid modeling, exploring different building retrofit strategies, and investigating the long-term economic and social impacts of large-scale heat pump adoption.

The model uses a deterministic approach with a single realization of renewable generation, neglecting variations in local generation capacity and grid congestion. The assumption of sufficient grid expansions is acknowledged as a simplification. The model focuses on newly added capacities and doesn't incorporate changes in electricity demand beyond heat pumps and gas-fired power plant displacement. The study acknowledges limitations in representing geographical positioning of new renewable energy facilities and inter-annual weather variations, although these are considered through sensitivity analysis. Qualitative narratives from a limited number of plumbing and heating businesses may not fully capture nationwide variations in installer practices and capacity.