To predict a quantity of collected heat by a solar heat collector with high accuracy and achieve an economical and efficient system operation.

A hot water supply system includes: a heat pump (2) that stores heat and operates to circulate water for hot water supply in a hot water storage tank (1); and a solar heat collecting unit (3) that elevates a temperature of the water for hot water supply in the hot water storage tank with the solar heat energy. The hot water supply system further includes a control system (4), which acquires predicted heat collection information relating to changes in the quantity of collected heat by the solar heat collector unit, on the basis of predicted weather information relating to changes in the quantity of solar radiation and changes in outside air temperature, and on the basis of the actual system information relating to changes in the heat quantity of hot water supply by the hot water supply system and changes in the supplied heat quantity of the heat pump, and which controls the heat storage operation of the heat pump on the basis of the acquired predicted heat collection information.