Abstract: A thermally integrated system combining a water heater tank with a refrigeration unit in a manner whereby heat dissipated by the unit serves to heat the water in the tank, the efficiency of the unit being maintained despite changing temperatures in the water tank. In this system, an external line conducting the refrigerant and acting as an auxiliary condenser is extended between the compressor and the main condenser of the refrigerator unit. The external line first passes through the upper region of the tank where it acts in conjunction with a water jacket interposed in the tank outlet pipe as a heat booster, the line then running in a coiled formation through the lower region of the tank in heat exchange relation with the relatively cold incoming water supplied by an inlet pipe.