Because of the promotion of renewable energy in Japan, it is expected that house with solar panels installed will be approximately 7.5 million in 2030. The aim of this study was to evaluate the effect of the precooling operation. To this end, we measured indoor environmental factors, energy consumption, and skin surface temperature and heat loss using a thermal manikin under four conditions with different air conditioning operations in a zero-energy house. As a result, we found that a 6-h precooling operation is more effective than a 3-h precooling operation, and the radiant cooling system is more effective than the air conditioner to increase the photovoltaic (PV) generation self-consumption and to decrease the sales power from PV generation. Furthermore, we learned that the heat loss of the radiant cooling system was less than that of the convection cooling system (air conditioner).