How Geothermal HVAC Works | FurnaceCompare®

According to the Department of Energy, the average American household spends $2,200 a year on their utility bills – with the largest percentage (47%) of that spent on heating and cooling. 

That’s why geothermal HVAC is an exciting proposition for many homeowners – it can save you up to 83% on that expense.

Even more impressive, it does so while being the most environmentally friendly, efficient, and reliable home energy solution you can add to your house (more than solar and wind). 

And it’s all due to how it works. 

Here is how geothermal HVAC works… plus 4 compelling reasons it’s something worth considering for your home. 

How geothermal HVAC systems work

Imagine you have two cups sitting side by side – one full of water and one that’s empty. And then imagine you connected them so that the water was free to flow from one cup to another. 

The water level would equalize between the two of them, right? 

Heat behaves the same way. Warm things have more energy (full cup) than things that are cold (empty cup). And just like water, that energy will always try to find an equilibrium within its environment.

This is the principle geothermal HVAC works on – it provides a connection between the ground and the air in your home such that heat can flow between them (it also “pumps” heat from one to the other – more on that in a second). 

How geothermal HVAC can heat AND cool your home

Unlike the air in your home, the temperature of the ground remains constant year-round once you reach a depth of 30 ft. 

The actual temperature depends on where you live. But generally, it’s somewhere between “frigid winter” and “blazing hot summer”:

Note: soil temperatures are equal to groundwater temperature at depths of 30ft and below.

Since the ground is usually warmer than the air in the winter but cooler than the air in the summer, it’s possible to use the ground as both a source of heat to warm your home and as a place to put heat from inside your home when you want to cool it off.

Here’s how that is achieved in real life:


However, if you live in Minnesota, warming your house to 37ºF/2.7ºC probably doesn’t sound all that enticing. That’s where a special piece of equipment called a “geothermal heat pump” helps you warm your home to a comfortable level, even if the ground isn’t.

How a geothermal heat pump works

Geothermal heat pumps are the heart of a geothermal HVAC system. They make it possible to  “pump” heat out of the ground (or your home) as you would water from a lake. 

In fact, they are so effective, it’s possible to get hot water from soil that is cool to the touch. 

Here’s how they do it:


The refrigerant (a liquid that absorbs heat readily) evaporates into a gas when exposed to even a temperate heat source, like the water that’s circulating under your house. 

Once evaporated, that gas is then compressed back into a liquid using the compressor (an electric pump), which increases the temperature of the refrigerant further (as pressure increases, so does temperature, according to Gay-Lussac’s Law).

This hot, pressurized refrigerant is then quickly depressurized, which releases its heat (cools it off) so you can use it to warm your house. Or, it releases it into your ground array to cool your home off. 

Types of geothermal HVAC systems

The animation above shows a common configuration for a geothermal HVAC system: a vertical, closed, ground loop. However, there are several other configurations that you can use as well, each with different benefits.

Open-loop geothermal HVAC uses a body of water (like a well or a pond) as a heat source, constantly pumping new water through the pipes.

The advantages of an open-loop system are that they are typically easier to install. However, they are prone to fouling and corrosion, as the water source is not always as clean and consistent as it would be in a closed loop system.

Closed-loop systems recirculate the same water in the underground pipes and it is not refreshed from a pond or a well. These systems are more reliable, because once clean water is put in the pipes, the likelihood of it becoming dirty or causing corrosion is minimal.

Depending on how it is configured (vertical, horizontal, or another body of water), the cost of installation will fluctuate, usually depending on how much digging must be done.

Some homeowners even opt to add traditional HVAC equipment (like a small gas furnace) to augment their geothermal system. This makes the installation costs of geothermal HVAC more approachable, but at the expense of some long-term energy savings.

4 reasons to consider geothermal HVAC for your home

You may be wondering “if geothermal HVAC is so great, why doesn’t everyone have one?” 

In short, they are expensive ($3,000-$12,000) and disruptive to install on existing houses as a result of the digging involved. They are much more common in new construction.

However, it’s still worth considering for your existing home as the benefits are substantial. Here are 4 compelling reasons it still makes sense to invest in a geothermal HVAC system.

1. Geothermal HVAC is more eco-friendly than solar or wind

Of all of the eco-friendly tech that is available for your home today (like solar or wind power), geothermal is the most environmentally friendly of them all.

According to NatGeo:

“Geothermal HVAC systems remove four times more kilowatt-hours of consumption from the electrical grid per dollar spent than solar and wind power add to the electrical grid.” 

This means installing a geothermal HVAC reduces overall electrical consumption 4x more than installing solar or wind would, even though it still requires electricity from the grid to operate.

Geothermal Savings

2. Geothermal HVAC is more reliable than traditional HVAC

According to the Department of Energy, your average gas furnace and air conditioner each have a service life of 15 to 20 years as long as they are maintained properly (annually). 

Compare that to your geothermal system, where the heat pump will last for 20+ years and the pipes under your house for 50+ years, and it’s pretty clear that geothermal HVAC has a leg up on traditional gas furnaces or air conditioners.

3. Geothermal HVAC is clean, safe and quiet 

A single geothermal HVAC system, when sized correctly, can heat and cool everything in your home, including your water, your floors, the air, and more. 

And since there’s no open flame or burning of gas, you’ll have cleaner air and reduced risk of fires and carbon monoxide poisoning. 

Geothermal heat pumps also run very quietly and are indoors (meaning no complaints from the neighbors).

4. Geothermal HVAC saves you a lot of money

Since a geothermal HVAC system is moving heat (and not creating it with combustion), it can put out more heat energy than the power it uses to do so.

According to the Department of Energy, it is very common to have your system operate at 300%-600% efficiency… meaning for every dollar you spend to heat and cool your home, you get $3-$6 worth of effectiveness.

To put that into context, for the average American household paying $1,043 per year for HVAC ($2200 x 47%), that equates to a $689-$861 annual reduction in utility costs, with the actual amount depending on how efficiently their system operates.

To put that into context, if the cost of installation was $7,000 it would pay itself back in 8-10 years.

How much could a geothermal HVAC system save you?

Each geothermal HVAC system is uniquely designed for the home it’s installed in. Find out what it would take to install one in your home (and how much it could save you each year) by talking to a heating and cooling professional in your area today.

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