Geothermal Heat Pumps

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.

According to the EPA, geothermal heat pumps can reduce energy consumption and corresponding emissions up to 44% compared to air-source heat pumps. Geothermal heat pump systems allow for design flexibility and can be installed in both new and retrofit situations. Because they have no outside condensing units like air conditioners, there's no concern about noise outside the home. A two-speed GHP system is so quiet inside a house that users do not know it is operating: there are no tell-tale blasts of cold or hot air.

The previous information in this article came from the Department of Energy. Average water temperature in the Aiken area is 62 degrees. One of the biggest savings homeowner have found is that there heating bills have been significantly reduced with a geothermal system. The reason for this is that many homeowners no longer need auxiliary heaters which is found in all air to air heat pumps. Whereas a standard air to air system needs auxiliary heaters to maintain temperature in the house as the temperature outside falls, a geothermal system does not. This is because the water temperature remains 62 degrees no matter the temperature outside. Thus there is no need for auxiliary heaters.

On the cooling side, a standard 3-ton package water source unit has an EER of 19.6. Your standard 13 SEER air to air heat pump has an EER of around 11. So as you can see, a water source system is significantly more efficient on the cooling side as well.

In our area, most water source systems are open loop systems. In this type of installation, water comes from a well, and runs through the system. Once it has gone through the system, it then is discharge into a dry well, pond or is dumped on the open ground outside. You can also install water source systems with a closed loop. With a closed loop system, the system is filled with well water with an antifreeze additive and then closed up. You will have water lines running in the ground via a vertical line or in a horizontal position. However these systems are about 25% less efficient than an open loop system. Also there is the additional cost to install the closed loop. On average, a closed loop system will cost about $1500-$2000 extra per ton of air conditioning.

A water source system will in general cost an additional 15-20% over your standard air to air system(this is assuming you already have a well). However, it will quickly make up this difference in reduced electric cost. If you will be in your home for at least 5 years, you may want to consider the benefits of a water source system. Please call our office for more information. We're here to help!

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