Evaluating heat pump retrofit strategies for a typical domestic building in the UK
In 2022, domestic buildings accounted for 20% of the United Kingdom’s greenhouse gas emissions, largely driven by the combustion of gas and oil for space heating and hot water. Given the sector’s high dependence on fossil fuels, decarbonization is critical to achieving the UK’s 2050 Net Zero target. The adoption of heat pumps offers a particularly promising pathway, providing an efficient and low-carbon alternative to conventional gas boilers. AWHP systems typically operate at lower supply temperatures compared to conventional gas boilers, which necessitates modifications to the design and/or operation of existing heating systems. A key change involves upgrading the radiators to low-temperature ones to compensate for the lower supply temperature. However, extending the duration of heating schedule as an alternative approach may also be effective and could mitigate the need for radiator replacement. In this study, these two retrofit strategies are examined for a typical UK domestic building from the technical and economic aspects by developing a dynamic thermal model of a building, heated separately by an AWHP and by a gas boiler. The simulation results for the defined case studies were evaluated using key performance indicators (KPIs), including Annualized Net Present Value (ANPV), upfront cost, running cost, final energy demand, and the system’s ability to maintain indoor temperature within the comfort range. By using these KPIs and comparing these case studies, the research aims to identify the most cost-effective strategy to overcome the retrofit challenges associated with heat pump adoption in existing domestic buildings in the UK. The findings indicate that, under an appropriate operational strategy, an AWHP can supply a thermal comfort level equal to or higher than those of a gas boiler. Additionally, extending the heating duration, instead of upgrading the radiators, can provide similar or improved comfort in buildings while reducing overall costs.