Hot water and / or
heating system (100) with: - an
exhaust gas heat exchanger (120) which is in fluid-conducting communication with a
discharge unit (113) of a heating device (110) and is arranged in the
exhaust gas stream of the
discharge unit (113) in such a way as to exchange the amount of heat containing in the
exhaust gas stream; - a fluid storage unit (130) which is in fluid-conducting communication with the exhaust gas
heat exchanger (120), designed to absorb the amount of heat from the exhaust gas
heat exchanger (120) into a fluid contained in the fluid storage unit (130), - a
heat pump (140) which is in fluid-conducting connection with the fluid
storage tank (130) on the
cold side, designed to provide the heat quantity of the fluid of the fluid
storage tank (130) to the heating circuit (114) on the warm side of the
heat pump (140), and - a three-way valve (150) is interposed in a fluid-conducting connection between the
cold side of the
heat pump (140) and the fluid
storage tank (130), wherein the three-way valve (150) is designed to limit a maximum
inlet temperature of the fluid to the
cold side of the heat pump (140), characterized in that a storage device (160) is provided which is designed to store the amount of heat generated by the heat pump (140), and the storage device (160) is fluidly connected to the heating circuit (114) and to the warm side of the heat pump (140), so that return water of the heating circuit (114) can be preheated with the flow of the warm side of the heat pump (140) via the storage device (160).