Ground-coupled heat pump (GCHP) systems provide indoor comfort but contribute to greenhouse gas emissions and other impacts on human health, ecosystems, and resources. Life cycle assessment (LCA) methodology has been employed to evaluate the environmental impacts associated with GCHP systems, with an application in China. Previous studies have disregarded the effect of building cooling and heating load imbalances on the long-term operating performance of the system, relying on static COPs and annual average data to obtain the environmental impacts. In this paper, an LCA method based on dynamic electricity mix and energy consumption data was used to assess the longterm operational environmental impacts of a reversible GCHP system. Results indicated that using annual temporal resolution and neglecting long-term impacts lead to an average underestimation of 6.5 % for all indicators, with an underestimation of 9.2 % for Eutrophication Potential. Highlights/Key innovations  A life cycle assessment methodology of GCHP systems is developed using dynamic electricity mix and consumption data to improve precision.  A reversible GCHP model is coupled with a building energy simulation tool to obtain the dynamic energy consumption.  The influence of using three different temporal resolutions on the accuracy of the LCA results of GCHP systems is compared.  The impact of performance degradation due to seasonal building-load imbalance on the accuracy of the LCA results is evaluated. Practical implications This study highlights the importance of considering long-term system performance variation and improving the temporal resolution of energy consumption for life cycle assessment, providing a more accurate assessment of heat pump systems environmental impacts.