Geothermal Systems

Enlarge Photo

Geothermal heating and cooling systems for homes are ground-and-water-source heat pumps that basically move heat from one area to another. This is not to be confused with geothermal plants that tap into the earth’s energy to produce electricity.

Geothermal systems for the home use the constant temperature of the ground, at about 45 to 75 degrees, to heat and cool areas of a home. In the winter, the warmth from the ground is brought into a heat pump to warm a home, and in the summer the heat is removed from the house, much in the same way a refrigerator works.

An indoor geothermal heat pump uses electrically driven compressors and heat exchangers to concentrate the Earth’s energy and release it inside the home at a higher temperature. In typical systems, duct fans distribute the heat to various rooms.

Watch Video Geothermal is smart business: it's cost effective and energy efficient.

Costs start roughly at around $15,000 for a system capable of heating and cooling an average, 2,000-square-foot home. And much of that cost is in tapping the earth. Geothermal systems often require either vertical bore holes, dug several hundred feet deep, or horizontal arrays of piping placed 4 to 6 feet underground.

Horizontal arrays take up much more space, while several vertical wells may have to be dug for a home system. The depth of a well is dictated by how large the system must be to produce the amount of British thermal units (Btu) required to heat or cool your home. Polyethelyne tubing transports water or an antifreeze solution to the heat pump for use in the home.

Systems also come in open or closed loops. Open loop systems use water from a well or pond to circulate through the system, then discharge the water through a different pipe. Closed loop systems keep the water or antifreeze sealed within the system. A standing column well can use a well also utilized for domestic water and return the used water via the same bore hole, potentially saving extra digging costs.

The type of system that's best for you will depend on your needs, the geography and geology (standing column wells are often used in the northeast, where there is bedrock close to the surface). A 350-foot-deep domestic use standing column well can develop approximately 5 tons of heat transfer.