Decarbonising Residential Heating: A Systematic Review of Life Cycle Impacts for Residential and District Heat Pump Systems

Electrification of residential heating via heat pumps is a key aspect of the global strategy to reach Net Zero. This is because heat pumps which can convert electricity directly to heat will almost directly reflect the carbon intensity of the electricity they use. The reduction in greenhouse gas emissions is dependent on the raw materials used, the source and quantity of electricity consumed for operation and end of life management of heat pumps. Therefore, it is necessary to evaluate the climate change impact and other sustainability aspects of heat pumps on a life cycle basis. However, heat pumps may be installed for individual buildings or as part of a heat network that supplies multiple properties, with significant differences between them in impacts from material usage, installation and operation. This review aims to synthesise and analyse the latest research to compare the environmental impacts of domestic heat pumps at these different scales, for new-build and retrofit cases. Following PRISMA protocols, a systematic search of peer-reviewed literature from 2017–2025 was conducted using the Web of Science and Scopus databases. The keywords used are as follows: 'Heat pump', 'Life Cycle Assessment', 'Environmental impact assessment', 'District heating', 'Domestic heating'. The number of studies found on the Web of Science database was 1256, with 1605 found on Scopus. 1006 studies were removed as duplicates, and the amount studies after removing duplicates were 1857. The review focused on studies quantifying impacts beyond operational energy use, specifically targeting embodied carbon, ozone depletion potential (ODP), resource depletion and the coefficient of performance (COP). We found that the life cycle impacts are interlinked with many factors, such as the characteristics of the electricity grid, the temperature lift, and the type of heat pump. We also note that there are differences in the methodological approaches, including choice of functional units and system boundaries, which limit the ability to cross-compare studies by non-experts. Despite this, the conclusions drawn suggest that geothermal heat pumps perform better than air source heat pumps. Moreover, future life cycle assessment studies on heat pumps will benefit by integrating temporal and spatial variations, such as heat pump performance with respect to the ambient temperature, and electricity grid greenhouse gas emission factors. This can help prioritise the deployment at scale of heat pumps on a wider scale based on the sustainability benefits when compared to conventional heating systems. The synthesis reveals that while domestic heat pumps generally exhibit lower upfront embodied carbon, they are frequently associated with higher cumulative refrigerant leakage and lower real-world efficiencies due to suboptimal installation. Conversely, district heat pumps consistently show lower environmental impact per kWh of heat delivered in high-density urban zones (>50 dwellings/hectare), primarily driven by the integration of waste heat sources and professionalized maintenance which prevents performance drift.