The purpose of this study is to find out natural and social conditions to effectively reduce CO₂ emissions by installing ground source heat pump systems (GSHPs). This study estimates life cycle CO₂ reduction potential of GSHPs for air-conditioning in office buildings under various natural and social conditions. Six hundred and forty possible patterns are generated by combining the following four conditions: climate, air-conditioning systems used at present, scales of office buildings and CO₂ emission factors of grid electricity used. Based on the CO₂ reduction potential of each pattern, this study analyzes patterns under which the GSHPs installation can effectively reduce CO₂ emission. The analysis finds that the installation of GSHPs can reduce CO₂ emission for about 40% (250 patterns) of all the 640 patterns. In particular, the GSHPs installation allows for higher CO₂ reduction in patterns that meet following conditions: (1) when GSHPs substitute absorption chiller-heaters in the area where the CO₂ emission factors of grid electricity are low and (2) when GSHPs substitute air source heat pumps in cold areas. In addition, sensitivity analysis is conducted considering a decrease in CO₂ emission factors of grid electricity and the efficiency improvement of GSHPs in the future.