Abstract: Disclosed is a hot-water system including a water tank with a water inlet and a water outlet for storing air-conditioning water; a pump motor, connected to the water outlet of the water tank through a connection pipe at one end thereof, circulating the air-conditioning water in the water tank by a pumping operation; an instantaneous water heater, connected to the other end of the pump motor by a connection pipe, instantaneously heating the air-conditioning water being circulated by the pumping operation of the pump motor; and an air-conditioning member, connected to both of the instantaneous water heater and the water tank to form an air-conditioning fluid path of a closed loop and guide the flow of the air-conditioning water; wherein the surface temperature of the air-conditioning member is increased by the heat of the air-conditioning water heated by the instantaneous water heater.