Geothermal Heating: The Facts

Gas, oil, and coal furnaces are America's heating energy staples. For years, they have provided our homes with the answers to all our heating questions. But where do we turn if we want a cleaner heat source? Geothermal heating technology is at the forefront of the push to find a better, more efficient way to stay comfortable in cold weather.

How Common is Geothermal Heating?

The United States is one of the largest producers of geothermal energy in the world. It currently has seven geothermal power plants in seven states, producing 16.7 billion kilowatt-hours (kWh) of electricity. That’s the equivalent of 0.4 percent of the entire energy output of the United States.

Geothermal energy production in the form of electricity isn’t exactly the same as geothermal heating. But it is proof to the point that geothermal energy works. And it works everywhere. Geothermal heating systems can be found in homes in every state. Even Alaska.

Plus, there are over 50,000 new domestic geothermal installations in the U.S. every year, so it is more common than you might think.

What is Geothermal Heating?

Geothermal translates as "Earth’s heat".

True geothermal heating involves drilling a well shaft many kilometers deep into the earth to tap into the higher temperatures farther underground. The heat is then transferred to the surface. This method works for large scale applications like power stations.

Similar vertical systems are also common for domestic properties. A professional, usually a well drilling company, will use a drilling rig to dig a 4-inch to 6-inch borehole to a depth of around 300 ft to 500 ft. These long vertical coils give the homeowner access to tap the warm, stable temperature environment deep underground.

Vertical systems are also better if an aquifer is used to feed the coils. It works by drawing the water up from the earth and passing it through a heat exchanger and then returning the water to its source. It is super-efficient and has no negative impact on the planet, the atmosphere, or the aquifer.

More commonly, geothermal heating on a domestic level typically involves laying a system of water-filled polyethylene ground pipes, horizontally in a loop, at least six feet below the surface of the ground (typically below the frost line).

Because the earth absorbs heat from the sun’s rays, as well as rain, it stores this heat at a steady 45 to 75 degrees Fahrenheit. The liquid in the pipes increases in temperature as it warms in the soil, and, using heat pumps, this energy gets transferred into your home.

Types of Geothermal Heating Systems

Closed-Loop System

Typically, closed-loop systems circulate an antifreeze solution around polyethylene tubing, either submerged in water or buried in the soil. A heat exchanger then transfers the heat from the refrigerant in the heat pump and the solution in the coils.

The advantage of this geothermal heating system is that it can be used in either vertical, horizontal, or pond and lake applications.

  • Horizontal Closed Loop - This method is the most common and cost-effective system. Typically, two pipes are laid, either at differing depths, or side by side, to a maximum depth of six feet. One cheaper way of arranging the coils is to use the Slinky method. This uses less space, allowing for geothermal installations in compact locations.
  • Vertical Closed Loop - This is the method typically adopted by commercial businesses, public buildings, and schools. It also reduces the impact on the local environment. Either one shaft or multiple holes are dug, typically to a depth of between 100 ft and 500 ft and roughly 20 feet apart. Pipes are inserted and connected at the bottom to form a U-bend, creating a loop, which is then connected to the heat pumps inside the building.
  • Pond or Lake Closed Loop - If there is an open source of water nearby, a supply pipe is laid underground from the building to the water and coiled at least eight to ten feet below the surface. This is the cheapest way of creating geothermal heating.

Open-Loop System

Open-loop (also called a pump & dump) is an ideal option if you can tap into an underground water source like a well. It is the most inexpensive option by far, but some local and county authorities don’t allow this type of installation, so be sure to check.

Geothermal Heating Requirements

Whether you opt for the vertical or horizontal loop system, geothermal heating is not going to be practical for everyone.

If you live in a densely populated area, the chances of you having enough space to have a horizontal geothermal system installed are slim. You could opt for a vertical arrangement which only requires a few square feet of land. This will require specialized equipment.

Before you do anything though remember that digging deep into the earth carries the risk of hitting buried pipes or utility cables. Be sure you coordinate with local utilities before anyone starts digging.

By far, the most common option is the horizontal loop geothermal system. It also requires the most land. Let’s put this into perspective: 400 to 600 ft of pipework is required for each ton of energy needed. The average mid-sized home uses three times that energy so would need 1,200 ft to 1,800 ft of coils.

If you still want to retrofit geothermal heating, it is a wise investment. The great news is that fitting geothermal heating is recognized as one of the few home upgrades that qualify you for a federal tax credit of up to 30% of the total purchase costs of the system, this includes installation cost.

Also, if you are building a new home and you have a plot large enough to do the excavation to lay the loops, a geothermal heating system would be an excellent way to future-proof your home and reduce your reliance on increasingly expensive fuel costs.

Geothermal Heating Costs

We would always recommend you get a geothermal heating survey to determine the exact requirements and cost. Still, as a rule of thumb, the average 2,500 square feet home, with a heating and cooling load of 60,000 BTU (British Thermal Unit), can cost somewhere in the region of $20,000.

That is definitely a premium price for heating and cooling.

However, it's not the end of the story. First, there is a 30% federal tax credit. That drops the price considerably. Plus, many states and utility companies offer their own geothermal incentives. Check your local programs. You might be able to get additional tax rebates, interest-free efficiency loans, or just flat cash back.

And let us not forget about those lucrative long term savings.

The U.S. Environmental Protection Agency estimates that the savings on heating and cooling costs could be as high as $1,500 annually when compared to conventional HVAC products. That means that if you live in your home for eight years using geothermal heating and cooling, you could save up $12,000. At that rate the system has basically paid for itself. Moreover, many homeowners see a 10 - 20% return on their investment over the lifespan of their system.

6 Advantages of Geothermal Heating

1. Good for the Planet

Switching to geothermal heating not only saves you money in the longer term, but it also helps to reduce carbon emissions in the atmosphere. The Environmental Protection Agency rates geothermal heating as the most environmentally friendly, cost-effective, and energy-efficient heating technology available.

2. Efficient

Geothermal heating systems run super efficiently compared to traditional methods. A geothermal heating system can be as much as 500% more cost-effective. That means that for every $1 you spend to heat your home, it returns five times the efficiency.

When you compare geothermal heating to the most efficient gas furnaces, which have a rating of 98%, you get a clear idea of the advantages of going green.

3. Quiet Operation

Do you hate noisy air conditioner compressors? Install the geothermal operating components far from where they'll impact your peace of mind.

4. Less Likely to Malfunction

Your home and the Earth itself protects a geothermal heating system. Damaging wind and rain can't hurt a system it can't reach. And that means fewer long term operating problems for you.

5. Less Obtrusive

A conventional condenser squats outside your home. With geothermal, there is nothing bulky or conspicuous on your property.

6. Longevity

Geothermal heating lasts, on average, ten years longer than a conventional system. If serviced well, geothermal heating systems should last up to 25 years. Don’t just take our word for it, the Department of Energy agrees. And the coils buried in the ground should be good for 50 years plus!

Final Thoughts on Geothermal Heating

Geothermal heating is an increasing reality for many. Reducing our reliance on fossil fuels will no doubt be challenging. It will require complex solutions and participation across the spectrum of society. In the case of geothermal heating, the best news is that not only is it cleaner for the planet, it also saves you money month after month.

And while the initial outlay is daunting, the potential return of a basic ground-source system can be very lucrative. In only a few years, you could see your geothermal heating savings make up for the extra installation cost. Then you'll start getting a real return on your geothermal heating investment.

Given that geothermal heating is both better for the environment and our wallets, we should all be able to breathe a little easier.

2 comments (view/add)
  • JOHN
    Posted on 11/5/2021

    Good article! How close can the horizontal pipes be lead next to each other? Are units setup for different weather areas? Mine is mild 90 degree summer and below freezing for 2-3 months? in Snowflake AZ

  • Dan Danowski
    Dan Danowski from Ingrams
    Posted on 11/8/2021

    Normal horizontal loop installation uses a standard backhoe bucket which is 2 ft wide, and the lines are laid to the sides of the trench so they are separated by 2 ft. Both climate and soil type must be considered when the ground loop design is chosen. The unit itself is the same.

* All fields required.

Your email address will not be published. Comments will display after being approved by our moderators. Comments may be edited for clarity.