Geothermal Heat Pump

A geothermal, or ground-source heat pump uses the earth or ground water as the source of heat in the winter, and the "sink" for heat in the summer. For this reason, ground-source heat pump systems have come to be known as earth-energy systems (EESs).

Ground-source heat pumps come in various types - open vs. closed loop, deep wells vs. shallow ground loops, and ground-to-air (heats air in your house) or ground-to-water (heats water for radiant hydronic heating). Many of these systems can also heat your domestic hot water.

Make sure you have access for drilling or digging in the ground at your home, and investigate the geology of the ground (deep soil, shale, bedrock, etc.). There are two common layouts of ground loops - shallow (a network of pipes about 6 feet underground in a wide area), or deep (two to four holes drilled down 50 to 200 feet like water wells). Another option (though less common) is to use a lake or pond for heat exchange, which requires a significant body of water and may require environmental permits.

For equipment selection, look for the Energy Star label, and these three performance ratings when choosing (the higher the better):

• COP (Coefficient Of Performance)
• HSPF (Heating Season Performance Factor)
• SEER (Seasonal Energy Efficiency Ratio - more related to cooling)

The size of a heat pump is typically denoted in tons or BTU/hour (1 ton = 12,000 BTU/hour) and they are most commonly available sizes to heat larger homes (2-6 tons).

A highly energy efficient way to heat and cool a home, especially in a very cold or hot climate, because the ground stays at a moderate temperature year-round. A ground source heat pump can save you major dollars on your energy bill, and reduce your greenhouse gas emissions.

The first successful commercial geothermal heat pump was installed in Portland, Oregon, USA in 1948 at the Commonwealth Building. It is now designated a National Historic Mechanical Engineering Landmark.