To provide a solar heat water heater capable of effectively using hot water in a hot water storage tank without wasting the hot water by reducing waste heating by an auxiliary heat source machine only by selecting an energy saving mode by an operation part during the washing of dishes, hands or the like enabling the use of the hot water in the hot water storage tank as it is even if the temperature of the hot water is lower than preset temperature, having excellent handling performance and energy saving performance, capable of securely preventing hot-water filling in a bath having a temperature lower than a set temperature by mistake and the abrupt supply of cold hot water during the use of a shower, and having excellent operation stability and operability.

Normally, when the temperature of hot water in the hot water storage tank is lower than a set hot water supply temperature set by the operation part, a control part heats the hot water in the hot water storage tank by the auxiliary heat source machine. When the energy saving mode is selected by the operation part, even if the temperature of hot water in the hot water storage tank is lower than the set hot water supply temperature set by the operation part, the control part does not perform heating by the auxiliary heat source machine and supplies hot water in the hot water storage tank as it is.