To provide a convenient hot water supply system adopting waterline pressure as hot water supply pressure while using a heat pump heat source device, an electric heater effectively using night power and solar energy.

Heat is accumulated in a tank by circulating water or a liquid heat medium 4 in the tank to a heat absorbing coil 5 of a heat pump condenser by a circulation pump 12. A coil A4 communicating with a water pipe which is applied with direct pressure of the water pipe is provided in the tank. While staying in a coil A or flowing in the coil A at the time of supplying hot water, the temperature of tap water in the coil is raised to equal to or higher than a required temperature by heat transfer or heat conduction with water around the coil or the other liquid heat medium 4. Hot water can be additionally heated by the electric heater before flowing through a hot water supply mixing valve 14 and water or the other liquid heat medium in the hot water storing tank or the coil A4 can be heated by a coil B different from the coil A by using the heat medium sent by the circulation pump and heated up by the heat pump heat source device.