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The latest buzzword around the “Green”-Building water-cooler, isnt about Wind, or solar-arrays. According to TVA Geothermal ( suing the earth) heating and cooling units are rising in popularity, due to the extreme savings they offer over the long term. Npthing new, Geothermal heat pumps (sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps) have been in use since the late 1940s. Geothermal heat pumps (GHPs) use the constant temperature of the earth as the exchange medium instead of the outside air temperature. This allows the system to reach fairly high efficiencies (300%-600%) on the coldest of winter nights, compared to 175%-250% for air-source heat pumps on cool days.

While many parts of the country experience seasonal temperature extremes—from scorching heat in the summer to sub-zero cold in the winter—a few feet below the earth's surface the ground remains at a relatively constant temperature. Depending on latitude, ground temperatures range from 45°F (7°C) to 75°F (21°C). Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger.

As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.

A dual-source heat pump combines an air-source heat pump with a geothermal heat pump. These appliances combine the best of both systems. Dual-source heat pumps have higher efficiency ratings than air-source units, but are not as efficient as geothermal units. The main advantage of dual-source systems is that they cost much less to install than a single geothermal unit, and work almost as well.

Even though the installation price of a geothermal system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs are returned to you in energy savings in 5–10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps installed in the United States each year.

Efficiency advantages of geothermal systems

Geothermal heating systems can extract up to six times the heat energy they use in electrical energy. In other words, compared to electrical heating, they are at least three and up to six times more efficient.
Geothermal heating systems use far less electricity than traditional electric heating systems - as little as one sixth as much.
Savings in heating mode can be up to 3/4 of the cost of electrical heating, and savings in cooling mode can be up to 1/4 to 1/2 of the costs of running a traditional air conditioner. When you factor in virtually free hot water, the overall efficiency can be even higher.
A 1500 square foot house equipped with a geothermal heating and cooling system costs $30 to $50 per month to heat or cool in most US climates.

The disadvantages of geothermal systems are up-front costs, disturbances to your land during installation, environmental risks of direct exchange systems, legal conformance risks relating to open loop systems, and maintenance issues relating to open loop systems.

The advantages of geothermal boil down to low operating cost, long life, flexibility, and sustainability. The disadvantages of geothermal are primarily up-front cost and temporary disturbance to your landscape if you're installing your geothermal system in an established neighborhood. But even though the advantages far outnumber the disadvantages, the up-front cost is a disadvantage that keeps many people from taking the plunge.