A hot water storage type hot water supply system, comprising: a storage battery unit; a heat pump cycle including: a compressor; a radiator for heating water; an expansion valve; and an evaporator, the heat pump cycle circulating a first refrigerant through the compressor, the radiator, the expansion valve, and the evaporator in this order; a water storage tank for storing the water heated by the radiator; a first heat exchanger; a water circulation path for circulating the water in the water storage tank, the water circulation path circulating the water from the water storage tank through the first heat exchanger and the radiator in this order and returning the water again to the water storage tank; a second heat exchanger; a first path for circulating a second refrigerant through the second heat exchanger and the evaporator in this order; a second path for circulating the second refrigerant through the first heat exchanger and the second heat exchanger in this order, the second path being usable by switching from the first path thereto; a first temperature sensor for sensing temperature of the storage battery unit; a second temperature sensor for sensing temperature of the water stored in the water storage tank; and a controller for switching between the paths circulating the second refrigerant, wherein the evaporator cools the second refrigerant and air, the first heat exchanger performs a heat exchange between the water and the second refrigerant, the second heat exchanger performing a heat exchange between the storage battery unit and the second refrigerant, the controller controls the second refrigerant to flow in the first path when the temperature of the storage battery unit sensed by the first temperature sensor is higher than a first predetermined temperature TBh, the controller controls the second refrigerant to flow in the second path when the temperature of the storage battery unit sensed by the first temperature sensor is lower than a second predetermined temperature TBl lower than the first predetermined temperature TBh, and the controller controls to close the first path and the second path when the temperature of the storage battery unit sensed by the first temperature sensor is not lower than the second predetermined temperature TBl and not higher than the first predetermined temperature TBh. a storage battery unit; a heat pump cycle including: a compressor; a radiator for heating water; an expansion valve; and an evaporator, the heat pump cycle circulating a first refrigerant through the compressor, the radiator, the expansion valve, and the evaporator in this order; a compressor; a radiator for heating water; an expansion valve; and an evaporator, the heat pump cycle circulating a first refrigerant through the compressor, the radiator, the expansion valve, and the evaporator in this order; a water storage tank for storing the water heated by the radiator; a first heat exchanger; a water circulation path for circulating the water in the water storage tank, the water circulation path circulating the water from the water storage tank through the first heat exchanger and the radiator in this order and returning the water again to the water storage tank; a second heat exchanger; a first path for circulating a second refrigerant through the second heat exchanger and the evaporator in this order; a second path for circulating the second refrigerant through the first heat exchanger and the second heat exchanger in this order, the second path being usable by switching from the first path thereto; a first temperature sensor for sensing temperature of the storage battery unit; a second temperature sensor for sensing temperature of the water stored in the water storage tank; and a controller for switching between the paths circulating the second refrigerant, wherein the evaporator cools the second refrigerant and air, the first heat exchanger performs a heat exchange between the water and the second refrigerant, the second heat exchanger performing a heat exchange between the storage battery unit and the second refrigerant, the controller controls the second refrigerant to flow in the first path when the temperature of the storage battery unit sensed by the first temperature sensor is higher than a first predetermined temperature TBh, the controller controls the second refrigerant to flow in the second path when the temperature of the storage battery unit sensed by the first temperature sensor is lower than a second predetermined temperature TBl lower than the first predetermined temperature TBh, and the controller controls to close the first path and the second path when the temperature of the storage battery unit sensed by the first temperature sensor is not lower than the second predetermined temperature TBl and not higher than the first predetermined temperature TBh.