Objective. The energy consumption of Japanese residential sector has increased about 24% for the last two decades. Heat pump and photovoltaic system are effective to reduce CO₂ emissions. In this study, we have evaluated effects of heat pump and photovoltaic system in consideration of temperature and solar irradiation for each region in Japan. Generally, COP of heat pump depends on outside air temperature and generated energy from photovoltaic system is different by individual regions due to differences in solar irradiation and temperature.
Results and Discussion. In all regions, photovoltaic system can reduce the CO₂ emissions larger than 600 kg-CO₂/year, heat pump can reduce that larger than 200 kg-CO₂/year considering the average CO₂ emission intensity of Japanese electric power companies. The amount of CO₂ reduction in Tokyo is largest. On the other hand, the amount of CO₂ reduction in Sapporo is smallest because of low COP in winter. In the case of photovoltaic system with Pb-battery system, the amount of CO₂ emission reduction increase more than the double in all regions.
Conclusions. The effects of heat pump and photovoltaic system are evaluated for each region in consideration of temperature and solar irradiation. In the case using the each CO₂ emission intensity of each Japanese electric power company, photovoltaic are very attractive for install. However, heat pump system is not suitable for the region with high CO₂ emission intensity on electricity. Pb-battery system is effective for photovoltaic system for storage in case there is surplus electricity. For heat pump system, the improvement of COP at low temperature enables the more reduction of CO₂ emission. The annual amount of CO₂ emission reduction in Sapporo with heat pump system will increase with improving COP of 5%.