A hot water storage type heat source device, comprising: a boiling section having a heating section for heating water with electric power from a peak cut power source whose power supply may be stopped on account of a power supply side; a hot water storage section for storing hot water heated by the boiling section; and an indoor-side utilization section for receiving electric power supplied from a commercial power source other than the peak cut power source and utilizing the hot water stored in the hot water storage section as a heat source for at least either heating or hot water supply on an indoor side, wherein when electric power supply from the peak cut power source is stopped and thereby the boiling section is stopped, the indoor-side utilization section operates with electric power from the commercial power source, characterized in that: the indoor-side utilization section: has a priority setting section for setting a priority between the indoor side heating and the indoor side hot water supply; and performs the indoor-side heating or the indoor-side hot water supply in preference to either one of the operations based on the priority set by the priority setting section when the boiling section is stopped due to stop of electric power supply from the peak cut power source and so the indoor-side utilization section operates with electric power from the commercial power source. a boiling section having a heating section for heating water with electric power from a peak cut power source whose power supply may be stopped on account of a power supply side; a hot water storage section for storing hot water heated by the boiling section; and an indoor-side utilization section for receiving electric power supplied from a commercial power source other than the peak cut power source and utilizing the hot water stored in the hot water storage section as a heat source for at least either heating or hot water supply on an indoor side, wherein when electric power supply from the peak cut power source is stopped and thereby the boiling section is stopped, the indoor-side utilization section operates with electric power from the commercial power source, characterized in that: the indoor-side utilization section: has a priority setting section for setting a priority between the indoor side heating and the indoor side hot water supply; and performs the indoor-side heating or the indoor-side hot water supply in preference to either one of the operations based on the priority set by the priority setting section when the boiling section is stopped due to stop of electric power supply from the peak cut power source and so the indoor-side utilization section operates with electric power from the commercial power source. the indoor-side utilization section: has a priority setting section for setting a priority between the indoor side heating and the indoor side hot water supply; and performs the indoor-side heating or the indoor-side hot water supply in preference to either one of the operations based on the priority set by the priority setting section when the boiling section is stopped due to stop of electric power supply from the peak cut power source and so the indoor-side utilization section operates with electric power from the commercial power source. has a priority setting section for setting a priority between the indoor side heating and the indoor side hot water supply; and performs the indoor-side heating or the indoor-side hot water supply in preference to either one of the operations based on the priority set by the priority setting section when the boiling section is stopped due to stop of electric power supply from the peak cut power source and so the indoor-side utilization section operates with electric power from the commercial power source.