A water heater comprising: a refrigerant circuit including a compressor, a condenser connected to a water circulation circuit, an expansion device, and an evaporator; a tank provided in the water circulation circuit, the tank storing water heated in the condenser; a feeding device provided in the water circulation circuit, the feeding device feeding water to the tank of the water circulation circuit; a first detecting unit configured to detect an outside air temperature; and a controller (Cnt) configured to control the compressor, the expansion device, and the feeding device based on a detected outside air temperature of the first detecting unit, wherein the controller (Cnt) includes an operation control unit configured to control operations of the compressor, the expansion device, and the feeding device,_a heat quantity acquisition unit that acquires a remaining hot water heat quantity that is a quantity of heat of water in the tank, and a storage heat acquisition unit that acquires a target heat storage quantity in the tank, when the operation control unit starts heating operation for storing heated water in the tank, the operation control unit starts operating both the compressor and the feeding device together, the operation control unit is configured to operate the compressor at a first compressor rotation speed until a preset first time period elapses from when the heating operation is started, after a lapse of the first time period, the operation control unit is configured to operate the compressor at a second compressor rotation speed higher than the first compressor rotation speed, characterized in that the operation control unit is configured to operate the feeding device at a first feeding rotation speed until a preset second time period elapses from when the heating operation is started, and after a lapse of the second time period, the operation control unit is configured to operate the feeding device at a second feeding rotation speed lower than the first feeding rotation speed. a refrigerant circuit including a compressor, a condenser connected to a water circulation circuit, an expansion device, and an evaporator; a tank provided in the water circulation circuit, the tank storing water heated in the condenser; a feeding device provided in the water circulation circuit, the feeding device feeding water to the tank of the water circulation circuit; a first detecting unit configured to detect an outside air temperature; and a controller (Cnt) configured to control the compressor, the expansion device, and the feeding device based on a detected outside air temperature of the first detecting unit, wherein the controller (Cnt) includes an operation control unit configured to control operations of the compressor, the expansion device, and the feeding device,_a heat quantity acquisition unit that acquires a remaining hot water heat quantity that is a quantity of heat of water in the tank, and a storage heat acquisition unit that acquires a target heat storage quantity in the tank, when the operation control unit starts heating operation for storing heated water in the tank, the operation control unit starts operating both the compressor and the feeding device together, the operation control unit is configured to operate the compressor at a first compressor rotation speed until a preset first time period elapses from when the heating operation is started, after a lapse of the first time period, the operation control unit is configured to operate the compressor at a second compressor rotation speed higher than the first compressor rotation speed, characterized in that the operation control unit is configured to operate the feeding device at a first feeding rotation speed until a preset second time period elapses from when the heating operation is started, and after a lapse of the second time period, the operation control unit is configured to operate the feeding device at a second feeding rotation speed lower than the first feeding rotation speed.