A combined device (40, 50) for heating domestic water and water for heating a room, said combined device (40, 50) comprising: - a storage tank for domestic water with cannulas, - a domestic water circuit in fluid communication with the storage tank, - a domestic water heating circuit in fluid communication with the storage tank, - a heating water circuit, - a heating water heating circuit, - one or several heat exchangers (41, 42, 58) for a heat pump in which a heat transfer fluid of the heat pump is able to circulate, the heat exchanger(s) (41, 42, 58) being configured to perform a heat exchange: • between the heat transfer fluid and a fluid present in the domestic water heating circuit, and • between the heat transfer fluid and the heating water present in the heating water heating circuit, in which the domestic water heating and heating water heating circuits are separate, the heat exchanger(s) (41, 42, 58) being arranged outside the domestic water storage tank, in which each of the domestic water heating and domestic water distribution circuits is in fluid communication with the storage tank at a suction orifice and a discharge orifice for the domestic water each formed at a cannula arranged inside the storage tank such that: - the suction orifice of the domestic water heating circuit is arranged in the lower part of the storage tank, - the discharge orifice of the domestic water heating circuit is arranged in the median part of the storage tank, - the suction orifice of the domestic water distribution circuit is arranged in the upper part of the storage tank, - the discharge orifice of the domestic water distribution circuit is arranged in the lower part of the storage tank. - a storage tank for domestic water with cannulas, - a domestic water circuit in fluid communication with the storage tank, - a domestic water heating circuit in fluid communication with the storage tank, - a heating water circuit, - a heating water heating circuit, - one or several heat exchangers (41, 42, 58) for a heat pump in which a heat transfer fluid of the heat pump is able to circulate, the heat exchanger(s) (41, 42, 58) being configured to perform a heat exchange: • between the heat transfer fluid and a fluid present in the domestic water heating circuit, and • between the heat transfer fluid and the heating water present in the heating water heating circuit, • between the heat transfer fluid and a fluid present in the domestic water heating circuit, and • between the heat transfer fluid and the heating water present in the heating water heating circuit, in which the domestic water heating and heating water heating circuits are separate, the heat exchanger(s) (41, 42, 58) being arranged outside the domestic water storage tank, in which each of the domestic water heating and domestic water distribution circuits is in fluid communication with the storage tank at a suction orifice and a discharge orifice for the domestic water each formed at a cannula arranged inside the storage tank such that: - the suction orifice of the domestic water heating circuit is arranged in the lower part of the storage tank, - the discharge orifice of the domestic water heating circuit is arranged in the median part of the storage tank, - the suction orifice of the domestic water distribution circuit is arranged in the upper part of the storage tank, - the discharge orifice of the domestic water distribution circuit is arranged in the lower part of the storage tank. - the suction orifice of the domestic water heating circuit is arranged in the lower part of the storage tank, - the discharge orifice of the domestic water heating circuit is arranged in the median part of the storage tank, - the suction orifice of the domestic water distribution circuit is arranged in the upper part of the storage tank, - the discharge orifice of the domestic water distribution circuit is arranged in the lower part of the storage tank.