The gas and the kerosene energy consumption are big for a hot water supply system as well as the percentage of the carbon dioxide emission rate is big in the plumbing system. A possibility of the carbon dioxide reduction by a hybrid hot-water supply system that a HP water heater by electricity is used as a base and big peak hot water load time of the fluctuation uses the boiler and the water heater by the kerosene and the gas and a problem are considered.