To provide an electric power-saving building having a storage/discharge device for storing electricity at nigh and discharging in the daytime when necessary, and an inverter device for arranging a wind power generation and photovoltaic panel as a power generation facility and discharging in response to the peak of use of electric power.

The storage/discharge device 12 is arranged for storing the electricity at night and discharging in the daytime when necessary. A storage/supply device 13 is arranged for storing residual hot water of a bathtub 8 and rainwater as reuse water and supplying the reuse water to a washer 9, a urinal 10 and a toilet bowl 11 of a toilet when necessary. The storage/discharge device 12 and the storage/supply device 13 are arranged in an underfloor space 4. The storage/discharge device 12 is connected via power storage electric wiring 21 to a part of electric wiring 14 positioned on the upstream side of a watt-hour meter 16, and is connected via discharge electric wiring 22 to the part of the electric wiring 14 positioned on the downstream side of the watt-hour meter 16.