HEAT PUMP WATER HEATER

PROBLEM TO BE SOLVED: To provide a heat pump water heater capable of performing defrosting operation according to outside temperature, temperature of an air heat exchanger, an amount of frost formation of the air heat exchanger, and an amount of stored liquid in a tank. SOLUTION: The heat pump water heater 100 includes a heat pump unit 30, a hot water storage unit 40, and an operation control device 50 and can perform defrosting operation for defrosting the air heat exchanger 4 of the heat pump unit 30. The operation control device 50 determines whether the defrosting operation is necessary or not, and further determines timing of starting the defrosting operation, based on a criterion for determining to start defrosting in which a determination result is set in every section according to the outside temperature and the temperature of the air heat exchanger 4 and in which the timing of starting the defrosting operation is set according to a hot water storage amount of the hot water storage tank 9. The operation control device 50 determines the end of the defrosting operation based on a criterion for determining to end defrosting in which temperature for ending defrosting is set in every section according to the outside temperature. COPYRIGHT: (C)2011,JPO&INPIT