In addition to improving energy efficiency, increasing the electrification rate in the commercial and residential sectors is regarded as an important CO2 emission reduction measure to achieve carbon neutrality in Japan’s capital city, Tokyo, by 2050. Here, the AIM/Enduse energy model was used to examine the pathways available for achieving carbon neutrality in the commercial and residential sectors of Tokyo by introducing both electrification and high-efficiency equipment. It was found that in order to reduce CO2 emissions to zero, it is necessary not only to reduce the CO2 emission factor for electricity to zero, but also to make electrification mandatory for both new and existing buildings and residences after 2030. In contrast, if the electrification mandate is limited to only newly constructed buildings and residences, consumption of fossil fuels such as city gas will remain, resulting in CO2 emissions of about 5.0 Mt CO2 in 2050. The results indicate the importance of making electrification mandatory to achieve carbon neutrality.