Environmental life cycle assessment of heating systems in the UK: Comparative assessment of hybrid heat pumps vs. condensing gas boilers

[Display omitted] •Life cycle assessment is used to assess environmental impacts of space heating.•Hybrid heat pump and condensing gas boiler are compared for a typical UK’s house.•UK electricity mix is identified as a key driver of hybrid heat pump’s impacts.•Hybrid heat pump could reduce up to 45% of GHG emissions vs condensing gas boiler.•The reduction in GHG emission could come with increase in water and metal depletion. Residential space heating is one of the major contributors to greenhouse gas (GHG) emissions and hence a priority sector to decarbonise in the transition to Net Zero target by 2050 in the UK. To assess environmental impacts of a current heating system and potential alternatives in the UK, this study conducted a comparative LCA of a condensing gas boiler and a hybrid heating pump for a common type of UK’s existing houses (a semi-detached house). The functional unit of this study is defined as delivering space heating for the whole lifetime (20 years) of heating system. The results suggest that the hybrid heat pump potentially saves 30% of GHG emissions as compared to the condensing gas boiler in the core scenarios (4.5E + 04 kg CO2-eq/FU vs 6.4 E + 04 kg CO2-eq/FU respectively). The hybrid heat pump also shows 13% to 48% emission reduction as compared to the condensing gas boiler in terrestrial acidification, photochemical oxidant formation, particulate matter formation and fossil depletion. However, the hybrid heat pump emits 3 to 6 times more emissions in terms of human toxicity, water depletion and metal depletion than the condensing gas boiler. The production phase contributes around 50% of the impact for metal depletion and human toxicity in both core scenarios, while the use phase dominates in other selected impact categories. The combustion of natural gas and the electricity production are the major causes for the dominance of the use phase for all selected impact categories excepting metal depletion and human toxicity. The sensitivity scenarios support the robustness of the results. Further work is needed to understand the role hybrid heat pumps can play in the residential sector decarbonisation under different scenarios of residential uptake, household behaviour and wider UK energy system decarbonisation.