The air-coupled electric heat pump has proved to be an economically viable device for space heating and cooling in many localities. The open-loop water-coupled heat pump has also proved its competitiveness where favorable conditions exist. The ground-coupled (closed-loop) heat pump appears to have characteristics that make it even more suitable for most situations.

Interest in the ground-coupled heat pump’s ability to reduce both energy use and demand has led to a number of research activities in several countries. The research effort has included both controlled laboratory studies and demonstration studies in occupied homes. This paper describes a part of these activities and furnishes some typical results of the studies. More complete information on the tests and results are described in the references.