Heat pumps are a promising technology to reduce greenhouse gas emissions (GHGE). Their use benefits from decarbonization of the national electricity mixes across the EU, as running on cleaner electricity would reduce the emissions associated with the heat generated from heat pumps. The study aimed to perform a life cycle assessment (LCA) to compare the impact of using heat pumps as a heating source in Slovenia and Serbia under different electricity scenarios that align with measures presented in National Energy and Climate plans. The results show significant differences in the environmental profiles of Serbian and Slovenian electricity sectors and improvements from the current to the future mixes (2030) with a higher share of renewables such as photovoltaics. In the impact category of global warming, an 84.7 % higher value of 1 MJ of heat produced by ground source heat pump in Serbia (0.080 kg CO2 eq) was observed compared to Slovenia (0.033 kg CO2 eq) and 85.9 % higher value compared to Europe (0.032 kg CO2 eq). The reduction in the impact category global warming in NECP 2030 scenarios that model reduction in coal and increase solar PV was observed in both countries (-17.1% Serbia; -28.6 % Slovenia). On the other hand, an increase in the impact category of mineral resource scarcity was observed, with values higher in Slovenia than in Serbia due to a higher share of PV. The study demonstrates that LCA provides a powerful tool to consider GHGE reduction and other environmental impacts, such as land use and mineral resource scarcity, and it can be used to support decision-makers dealing with future national energy plans and decarbonization strategies.