Recently, renewable energy has been penetrated into power supply in Japan. However, the high penetration of renewable energy causes a surplus of electricity. Reducing the surplus, the control methods of demand using household equipment have been proposed. In this study, we focused on heat pump water heaters (HPWHs). We simulated operation of HPWHs controlled to reduce the surplus. we simulated the supply-demand balancing of power system with the power demand of HPWHs. We evaluated the effect of contribution to power system to control HPWHs to reduce the surplus electricity from the viewpoint of the amount of surplus, CO2 emission, and fuel costs.