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Tap Into the Energy Under Your Feet

One of the most efficient, proven ways to mechanically heat and cool a home is with a Ground Source Heat Pump, also known as a Geothermal Heat Pump (GHP). As a matter of fact, the Environmental Protection Agency calls GHPs the most energy-efficient, environmentally clean, and cost-effective space conditioning system available. Most are ENERGY STAR qualified.

Geothermal heat pumps work similarly to conventional air source heat pump systems, but are much more efficient because they take energy from and discharge energy to the ground instead of the air. GHPs are 50-70 percent more efficient at heating and 20-40 percent more efficient at cooling than conventional systems. GHPs take advantage of the earth's relatively constant temperature to provide heating, cooling, and hot water. During the summer GHPs produce essentially free domestic hot water from the home's waste heat as a byproduct of the thermal process.

A GHP system will cost $2,000 to $3,000 (50-65 percent) more than a conventional gas furnace/standard AC or air source heat pump, but will usually pay off in lower utility bills within three to five years. Over the life of a GHP system, you can anticipate saving upwards of $20,000. Rebates and other financial incentives can further reduce the purchased price of a GHP system. Rebates and low interest loans are often offered by local utilities. Tax credits, tax exemptions, and low interest loans are often offered by many states. The Federal government offers low interest loans.

In addition to the substantial savings in heating, cooling, and water heating costs:

  • Geothermal heat pumps last longer than conventional systems because they are protected from harsh outdoor weather. The unit is housed indoors and the loop underground. They have fewer mechanical components, making them more reliable and less prone to failure. The ground loop has an expected life of over 50 years and requires no maintenance.
  • As with most heat pump systems, geothermal heat pumps do not burn fossil fuels and there is no need to vent exhaust fumes. Outside air is needed only for proper ventilation, keeping the inside cleaner and minimizing pollens, outdoor pollutants, mold spores and other allergens.
  • Geothermal heat pumps have no exposed, noisy outside units. The unit operates quietly without disturbing the owner or the neighbors.

The ducting and heating/cooling distribution system inside a house is no different with a GHP than with any other forced-air system. Therefore, geothermal heat pump systems are easy to retrofit into houses with existing forced-air systems. However, there must be enough space outside in which to bury the ground loop through which the heat is transferred.

GHPs work by moving heat, rather than by converting chemical energy to heat like in a furnace. Every GHP system has three major subsystems or parts: a geothermal heat pump to move heat between the building and the earth, a buried pipe or ground loop for transferring heat between its fluid and the earth, and a distribution subsystem for delivering heating or cooling to the building. Each system may also have a desuperheater to supplement the building's water heater, or a full-demand water heater to meet all of the building's hot water needs.

In heating mode, heat is extracted from the fluid in the earth connection by the geothermal heat pump and distributed to the home or building -- typically through a system of air ducts. Cooler air from the building is returned to the geothermal heat pump, where it cools the fluid flowing to the earth connection. The fluid is then re-warmed as it flows through the earth connection.

In cooling mode, the process is reversed. The system pulls heat from the building, carrying it through the system and placing it in the ground. This process creates free hot water in the summer and delivers substantial hot water savings in the winter.

For related information, manufacturers, suppliers, pricing, and economic analyses consult these links:


Geothermal Heat Pump Consortium

International Ground Source Heat Pump Association

US Department of Energy - Geothermal Heat Pumps

Content updated on 8/3/2006

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