A horizontal loop field can be less expensive than vertical drilling but requires more space, as shown at this larger installation at an electric co-op.
Courtesy of Federated Rural Electric Association (Minnesota)
Q: I am planning to replace my current heating system with a geothermal heat pump. It is comparatively pricey, but it seems like an efficient option, and I like that it includes air conditioning. Is this a good idea?
A: In most areas of the U.S., space heating and cooling account for a large percentage of home-energy use, so upgrading to a more efficient HVAC system is a great way to reduce your monthly energy bill. A geothermal heat pump, also known as a ground-source heat pump, is among the most efficient types of heating and cooling systems you can install.
Even when it is extremely hot or cold outside, the temperature a few feet below ground remains relatively constant and moderate. A geothermal heat-pump system uses this constant ground temperature to heat and cool your home. According to the U.S. Environmental Protection Agency, geothermal heat pumps use up to 44 percent less energy than traditional air-source heat pumps and up to 72 percent less energy than electric-resistance heaters combined with standard air conditioners.
A geothermal heat-pump system has three main components:
- A collector, or loop field, which is in the ground and cycles a liquid, like antifreeze, through dense, plastic tubing
- A heat pump in your home
- A duct system that distributes heated or cooled air throughout your home
During winter, the collector absorbs the heat stored in the ground, and the liquid carries that heat to the heat pump, which concentrates it and blows it into the ductwork, warming your home. In the summer, the heat pump extracts heat from the home and transfers it to the cooler ground.
The collector can be set up in one of three ways:
- Horizontal system: Plastic tubing is placed in trenches four to six feet below the ground surface. This system works well for homes or businesses with sufficient available land, as it may require up to 400 feet of trenches.
- Vertical system: If the site doesn’t have space for a horizontal system, a collector can be placed vertically. A drill digs 100 to 400 feet below the surface and places the tubing. This system can be more costly but will have less impact on existing landscaping and can be used on smaller lots.
- Pond system: For homes with access to a pond or lake, a pond system (also called a water-source heat pump) may be possible. The loop field is connected to the heat pump and then placed at least eight feet below the surface of the water. This option can be the lowest cost.
Geothermal systems typically cost more than other heating systems, largely because of the collector and the associated digging or drilling, but their high efficiency can help reduce the payback time. The cost will vary based on whether new ductwork is needed and the type of collector you install, among other factors. Incentives are available for those who install qualified geothermal heat pumps—most notably, a 30 percent federal tax credit for installing an Energy Star-rated system before the end of 2016. So, if your system and installation cost $20,000, you could take $6,000 off your federal tax bill. South Carolina is offering a 25 percent state tax credit on geothermal equipment and installation through Dec. 31, 2018.
For those with high heating and cooling bills, an efficient geothermal system is a good option to consider. People building new homes should also consider, before construction, whether to install a geothermal heat pump. The system can be included in the mortgage, and installing it before the home is completed means no disruption to your landscaping.
Send questions to Energy Q&A, South Carolina Living, 808 Knox Abbott Drive, Cayce, SC 29033, email email@example.com or fax (803) 739-3041.
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