Abstract: This invention combines a hot water heater which conventionally supplies hot water for household use, a hot air furnace and an air conditioning evaporator coil conventionally provided in the plenum of the furnace as a component of a central air conditioning system, by means of pipes from the hot water heater to the air conditioning evaporator coil. Hot water heated by the hot water heater circulates through the evaporator coil which becomes the heat source for the air moving through the furnace and ductwork throughout the house. Valve means are provided in the water pipe lines to isolate the hot water heater from the air conditioning evaporator coil when the coil is used as a component of the air conditioning system during the summer months. Valve means are provided in the air conditioning lines to isolate the coil from the air conditioning compressor and condensor unit during the winter months.