Assessing the impact of air source heat pump retrofits on indoor environment and energy consumption in UK homes

<p dir="ltr"><i>To support the UK target of net zero emissions by 2050, the Government aims to install 600,000 heat pumps annually by 2028. This study examines the impact of air source heat pump (ASHP) retrofits on indoor comfort and household electricity consumption across 16 diverse dwellings in an Oxford neighbourhood. A mixed-method approach combined household surveys with continuous monitoring of indoor and outdoor temperature and relative humidity. Data were collected over two periods: 1 December 2024 to 6 February 2025, when heat pumps supplied space heating and hot water, and 21 June to 31 August 2024, when they provided hot water only. Smart meter data from three homes offered additional insights into electricity consumption patterns. Indoor temperatures remained above the World Health Organisation recommended minimum of 18°C, but often below the 20°C threshold advised for vulnerable groups in winter. Surveys indicated improved comfort and satisfaction post-installation, with most users finding the systems easy to operate and willing to shift energy use, though challenges in maintaining consistent room temperatures were reported. Mean daily electricity consumption ranged from 18.6 to 24.3 kWh in winter and 4.10 to 10.62 kWh in summer. Peak demand generally occurred outside the 4–7 pm peak period, with the highest usage (0.85 kWh) observed at 7 pm in one dwelling, likely reflecting lifestyle factors. These findings highlight the influence of ASHPs on indoor environments and energy demand, underlining the role of time-of-use tariffs and smart controls in promoting off-peak usage. The study provides evidence to guide scalable, equitable strategies for UK residential heat decarbonisation.</i></p>