Abstract: An integrated apparatus for producing warm or sanitary water, comprising in combination a heat pump having a compressor, a condenser, an expansion valve and an evaporator connected in series to convey a refrigerating fluid, an electric or fuel-powered (gas- or gas oil-powered) boiler accommodating the condenser of the heat pump, and at least one greenhouse effect heat source. A chamber for receiving the evaporator of the heat pump is provided downstream of the boiler and is in communication both with the boiler to receive therefrom the flue gases and with the greenhouse effect heat source to receive therefrom warm air which, together with the exhaust fumes, gives off heat to the evaporator.