Optimum design of PV and SWH for all-electric house

Since nuclear power plants are shut down and working rate of thermal power plants are increasing, the buying electric rate is going to change in Japan. Although, selling electric rate of photovoltaic system (PV) is now 42 yen/kWh by feed-in tariff, the selling electric rate may drop after 10 years by the expired feed-in tariff. This paper concentrates on the optimum unit size of the PV and the solar water heater (SWH) system according to change electric rate. The simulation results show that it is better to apply unit size of PV as higher as possible. Solar thermal energy is enriched by raise of buying electric rate.