Abstract: Apparatus and a method for using terrestrial heat to increase the temperature of a liquid, such as water. A circulation pipe buried in the earth in a region of high subterranean heat allows the liquid to move in heat exchange relationship to the subterranean heat. The liquid is pumped from a tank adjacent to the surface of the earth and through the pipe back to the tank. The heated water in the tank can be removed from the tank and caused to flow through a heat exchanger also adjacent to the surface of the earth. Then, the water is returned to the tank for re-use and reheating.