What is Geothermal (Ground Source) Heating?

To many people, the word ‘geothermal’ conjures up images of molten lava and boiling geysers. Perhaps you’ve read about how Iceland gets much of its electricity by harvesting the thermal energy from the volcanic activity under the island. While that may work to keep the lights on in Iceland, most homeowners (thankfully) don’t have volcanoes or hot springs to tap into and keep warm in the winter. And yet, geothermal home heating and cooling is a popular, sustainable way to heat and cool buildings used by homeowners all over the world. So what, then is geothermal heating?

Simply put: geothermal heating and cooling is a fancy term for Ground Source Heat Pumps (GSHPs). A ground source heat pump, or geothermal heating system, uses ambient heat stored under your lawn, or a nearby body of water to keep you warm in the winter and cool in the summer. It’s the most efficient, cost-effective way to heat and cool your home, no molten lava necessary.

What Is a Heat Pump?

In the simplest of terms: a heat pump is a device that pulls BTUs (heat) from one place and transfers it to another. Anyone with a refrigerator may be surprised to learn that they have a heat pump in their home! Refrigerators work by transferring heat, measured in BTUs, from the inside of the fridge to the outside (your kitchen), keeping your veggies crisp and your leftovers, hopefully, edible. 

Heat pump technology is also used to heat and cool homes. When most people think of heat pumps, they think of air source heat pumps (ASHPs) like mini-splits. True to their name, air source heat pumps pull BTUs from the air outside and transfer them into homes to heat them. During the warmer months, the system works in reverse, with heat from the home being shifted outside to provide air conditioning.

A geothermal system, or ground source heat pump (GSHP) works in a similar way, but it pulls heat from the ground instead of the air. While the temperature of the air outside obviously varies, the temperature below the frost line stays consistent year-round. This allows a geothermal system to be able to pull BTUs to heat homes efficiently even on the coldest days of the year.
All heat pump systems operate using electricity. Air source heat pumps are often used to supplement fossil fuel heating systems because after the temperature drops to a certain degree, they can no longer efficiently pull BTUs to warm your home. Contrast that to a geothermal heat pump, which uses the consistency of ground temperature to operate at 300-600% efficiency no matter what the weather is outside.

How Does A Geothermal Heat Pump Work?

The earth absorbs heat from the sun all year round, storing it underground. That means that about eight feet under your lawn, the earth is a fairly consistent temperature all year round, about 55 degrees. A geothermal heating system taps into that temperature through underground pipes called “ground loops” that extract that heat to keep your home warm. Of course, while 55 degrees might sound balmy in the middle of winter, that’s not an ideal temperature for a comfortable home. That’s where the heat pump comes in. 

A mixture of water and food-grade antifreeze is pumped through the ground loops, absorbing that ambient temperature and bringing it into the heat pump. The heat pump, which replaces your boiler or furnace, uses a compressor and a heat exchanger to increase that 55 degree ground temperature to whatever you’d like. The heat pump would then distribute that warmth throughout the home through an HVAC system, the same way a traditional heating system would.

In the warm summer months, the system works in reverse and provides super efficient central air conditioning. Excess heat from the house is put back into the earth through the ground loops creating what’s called a “heat sink.” While disbursing the excess heat from your house, those ground loops continue to absorb that cool, 55 degree ambient temperature to cool your home. 

So to review: a geothermal system is a super-efficient way to heat and cool homes using the temperature of the ground under your lawn. Functionally, a geothermal heating system would operate in a similar way to any traditional home heating system like fuel oil, natural gas, or propane. You’d set your thermostat to your desired temperature and the ground source heat pump would get to work warming your house. A Geothermal system offers the best of both worlds; it doesn’t burn any fossil fuels to heat your home and the system also works in reverse, providing efficient central air conditioning in the summer.

Can Geothermal Heating Systems be Installed Anywhere?

Geothermal heating systems can be installed just about anywhere in the world. The Nordic countries of Sweden and Finland are world leaders in geothermal home heating and cooling. Despite being situated so close to the Arctic, one in every five homes in Sweden is heated by a ground source heat pump! The reason is surprisingly simple: once you get below the frost line, the earth maintains a consistent temperature just about everywhere. 

By harnessing heat from the consistent temperature of the ground, geothermal heat pumps operate at anywhere from 300-600% efficiency! Compare that to a modern, high-efficiency furnace that burns natural gas, which will cap out at around 98% efficiency. That efficiency means that geothermal heat can keep homes warm in even the coldest climates.

How Sustainable and Cost-Effective Is Installing Geothermal?

Another big misconception about geothermal is that it’s expensive, but in the long term it’s actually the most cost effective heating system. As any homeowner can tell you, a traditional heating system that burns fuel oil, natural gas, or propane will deliver high heating bills in exchange for a warm home in the winter. While geothermal may cost more to install up front, it also eliminates your heating bill altogether. In a 2020 Vox article, writer David Roberts crunched the numbers and determined that geothermal heating is “a better value than their competitors over the lifetime of the system.” 

To make the transition to geothermal even more painless, the federal government, states, and many utility companies offer generous cash incentives to make the switch. With Dandelion, you could even finance your upgrade to geothermal heating with no money down and pay as little as $140/month!

Of course, beyond the high cost of heating bills that inevitably come with fossil fuels, they also contribute harmful emissions that drive climate change. Because geothermal is so efficient, it can handle 100% of your heating needs, even on the coldest days, completely eliminating the need for fossil fuels in home heating. That means geothermal can help significantly reduce your home’s carbon footprint all while keeping you comfortable and saving you money.

Make the switch to Geothermal for as little as $0 down and $140/month.

To see if your home qualifies click here: