Geothermal heat pumps (GHPs), sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps, have been in use since the late 1940s. They 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% to 600%) on the coldest winter nights, compared to 175% to 250% for air-source heat pumps on cool days.
Although 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). Similar to the cave, ground temperatures are 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 multi-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.
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 year1.
Xcel Energy offers rebates only on closed-loop, ground source heat pumps, with a minimum 14.1 EER rating and 3.3 COP that are currently listed on the ENERGY STAR website. Additionally, the unit must include air cooling AND heating applications. Pond installations or “pump and dumps” are not eligible for a rebate. See the rebate application for additional details and requirements.
Please verify that the ground source (geothermal) heat pump you install is ENERGY STAR qualified by visiting energystar.gov or calling 866.STAR.YES (866.782.7937).
Ground Source Heat PumpsWhat is a closed loop ground source heat pump?
South Dakota
Information Sheet
For more information on geothermal heat pumps aka ground source heat pumps click on this link for an informative video from the Department of Energy.
Use this link to find out more information on rebates and eligibility for ground source heat pumps (GSHPs) in South Dakota.
Looking for more information regarding GSHPs? Here are some resources:
Energy Design Resources
Ground Source Heat Exchange
Department of Energy
National Geographic
National Renewable Energy Laboratory
GreenBuilding
EnergyStarGSHP Video
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Ground Source Heat Pumps Information Sheet
South Dakota
1 http://energy.gov/energysaver/articles/geothermal-heat-pumps2 https://energydesignresources.com/resources/e-news/e-news-73-ground-source-heat-pumps.aspx The U. S. Department of Energy report notes that “the modeled 2.9 coefficient of performance (COP) heating efficiency of the air-source heat pump is halfway between the cold weather (17°F) and
standard, mild weather (47°F) rating conditions of a new high-efficiency (FEMP-recommended and ENERGY STAR model). Similarly, the modeled cooling efficiencies of the air-source heat pump, gas furnace, and air-source air conditioner all represent models that just meet the FEMP-recommended and ENERGY STAR qualifying levels.” Original site energy use data converted to source energy use per EPA national conversion factors of 3.34 source kBtu per site kBtu for electricity use and 1.047 source kBtu per site kBtu for natural gas use.
U.S. Department of Energy Comparison of Energy Use1
20.00
18.00
16.00
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00Air-Source Heat Pump
Gas Furnace Air-Source AC
Energy Star GSHP
Best Availiable GSHP
Heating/ Cooling Efficiency*
11.0 EER 2.9 COP
11.0 EER 90% AFUE
14.1 EER 3.3 COP
25.38 EER 4.9 COP
Cooling Heating 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 to 10 years.
For more information regarding ground source heat pumps call one of our Energy Experts at call 800.895.4999 or email the Energy Expert Team at [email protected].
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