Abstract: A system for recovering heat from a geothermal well includes a quantity of heavy drilling mud filling the bottom of the geothermal well. A hollow heat absorber is disposed within the drilling mud in the well bottom. The heat absorber is supplied with a working fluid such as freon through a supply pipe extending from the top of the well, the pressure head of the working fluid at the heat absorber being commensurate with the depth of the well. A high pressure gas delivery pipe extends from the heat absorber to the top of the well, and is connected to a heat exchanger disposed within a water boiler. The outlet of the heat exchanger is connected to a working fluid supply tank, which is connected in turn to the upper end of the supply pipe. A thermostatic valve interposed between the supply tank and the supply pipe controls the amount of working fluid entering the heat absorber in accordance with the temperature and heat demands of the water boiler.