You're thinking of a geothermal heat pump which I do not think is what OP was talking about. Heat pumps are ac/furnace 2 in 1 systems that run on electricity. h

You're thinking of a geothermal heat pump which I do not think is what OP was talking about. Heat pumps are ac/furnace 2 in 1 systems that run on electricity. https://en.wikipedia.org/wiki/Heat_pump https://en.wikipedia.org/wiki/Heat_pump