Abstract: A system and method for heating water with heat obtained from liquid that is sourced by a ground-loop system, the system including a ground-loop heat exchanger, a compressor, a hot-water-reservoir-loop heat exchanger, a subcooler heat exchanger, and a thermostatic expansion valve. The ground-loop heat exchanger is structured to transfer heat from heated ground liquid to a refrigerant. The compressor is structured to increase a pressure of the refrigerant received from the ground-loop heat exchanger. The hot-water-reservoir-loop heat exchanger is structured to transfer heat from the refrigerant to water received from the hot-water reservoir. The subcooler heat exchanger is structured to transfer heat from the refrigerant to the ground liquid before returning the liquid to the ground-loop system, and the thermostatic expansion valve structured to control a flow of the refrigerant to the ground-loop heat exchanger.