How Does Geothermal Cooling Work?

Posted by Carl Taylor on July 21, 2015
How Does Geothermal Cooling Work?
Here is a diagram of geothermal systems so you can better picture what's happening.

Although the concept of geothermal energy is one that's been around since Ancient Romans were snap-whipping their buddies with towels while bathing in hot springs, it can still be unfamiliar to some people. That being said the idea of geothermal heating is not all too hard to comprehend – the Earth's core maintains a constant temperature year round and thus we can funnel that heat to warm our houses instead of a traditional furnace.

A common misconception of geothermal heating is that it is only used to heat the house, but the process can work in reverse to be a viable way to cool the home as well. This is where some of the confusion comes in; hot springs are understandable, but cool springs? Not so much.

The Geothermal Setup

To fully grasp geothermal cooling, you must first know the common setup of the system. Heating and cooling both operate on the same general foundation which includes:

  • Underground tubes to access the Earth;
  • A pump to circulate fluid through the tubes;
  • An air handler to convert the geothermal energy; and
  • Transfers heat from one source to another.

While these components definitely play a part in creating a comfortable home in all seasons, the real star is the Earth's core. After roughly 4 to 6 feet, the Earth maintains a constant 55°F temperature no matter if the air above is 100° or 20°. (For more information on the installation of a geothermal system, take a look at Geothermal Genius’s post here.)

Geothermal Heating

The geothermal concept that's easiest to understand is heating.

  1. The underground loops circulate a cold refrigerant/water mixture that absorbs heat from the 55°F temperature.
  2. An indoor heat pump absorbs this warmth from the liquid and the HVAC compressor intensifies the heat.
  3. An air handler then delivers this warmth to a home via a standard furnace duct system.
  4. Once the heat is sucked out of the refrigerant/water, the mixture cycles back out into the Earth loops to collect more heat.

Tip: Geothermal heating = warm fluid comes in the home, while cold fluid exits the home.

Geothermal Cooling

It's best to think of geothermal cooling as flipping the switch in reverse because that's what's literally being done on the heat pump. Here’s the geothermal cooling process:

  1. The indoor pump takes the hot air inside of the home and pumps it into the Earth via underground pipes, leaving behind cold air in its place. Specifically, the hot refrigerant coming out of the compressor (100+°) is sent to the Earth.
  2. The Earth’s natural processes absorb the heat. Then it quickly cools itself back down to its original 55°F temperature.
  3. The cooled refrigerant is then brought back to the home.
  4. Your air handler takes what is left by the refrigerant – cool air – and distributes it via a standard duct system.

Tip: Geothermal cooling = cold fluid comes in the home, while warm fluid leaves the home.

It's important to understand that cold will always be dominant whether it's when the cold refrigerant absorbs the heat or when the cooler Earth's core absorbs the hot coolant. Just imagine: Wouldn't it be nice to sit comfortably in your home without having to feel guilty about running the A/C?


Carl Taylor is an associate of Comfort Pro, an HVAC and geothermal installer. He has extensive experience and interest in common geothermal problems, installation techniques, and HVAC industry news. 

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