Geothermal Heat Pumps

March 28, 2020 | Posted In:

Geothermal heat pumps, also called ground-source heat pumps are a type of highly-efficient heating and air conditioning (HVAC) system. Geothermal heat pumps take advantage of the earth’s fairly constant and consistent temperature. The earth’s temperature is generally warmer than the air during the winter, and cooler than the air during the summer. In Western North Carolina, the ground temperature is around 55 degrees Fahrenheit.

Geothermal heat pumps heat buildings by transferring heat from the ground into buildings; they cool by transferring heat out of the building into the ground.

To heat a building in winter, a typical geothermal system pumps a mix of cold water and antifreeze through underground pipes where the mix is warmed by the surrounding earth. The warmed mix travels to an evaporator located in the building where the heat is transferred to a refrigerant and becomes a gas. A compressor increases the gas pressure which raises the temperature, providing heat for circulation through the duct work of the building. This heat can also be used with hot water heaters.

To cool a building in summer, the above process is essentially reversed; instead of removing heat from the ground, the water and antifreeze mix removes heat from the house and deposits it in the ground. This process is similar to how a refrigerator works, where cool refrigerant circulates to absorb and remove the heat inside a refrigerator.

By taking advantage of solar heat stored in the ground, a geothermal heat pump typically produces three times more energy than it consumes: 1 kW of electricity to operate the system yields 3 kW of heat. This is 25% to 50% less than a traditional air source heat pump. Geothermal heating systems significantly reduce peak energy demand, which drives the need for new power plant construction in our region. The initial purchase and installation cost for geothermal heat pumps is typically higher than for conventional HVACs, but they can quickly pay back the investment because they use less electricity. Geothermal heat pumps immediately reduce monthly utility bills, and the overall investment can usually be recouped in five to ten years. There is a Federal Tax Credit of 26% in 2020 and 22% in 2021.

Geothermal HVAC systems have been in use for decades and are widely available today. Major manufacturers include American Standard, Trane, Bosch, Carrier, Rheem, Lennox, Mitsubishi, and Dandelion Energy. Below is a list of local HVAC companies that install geothermal HVAC systems:

For more detailed information on this technology, we recommend visiting North Carolina Sustainable Energy Association’s page on geothermal heat pumps and the Department of Energy’s page on geothermal heat pumps.

Two helpful videos that explain how geothermal works:

  1. This Old House Video
  2. NYSERDA Video