Could your home benefit from a geothermal heating and cooling system? Geothermal systems are one alternative to conventional heating systems. Geothermal technology has been around since the 1940s and was initially used for water heating. Geothermal systems have advanced to provide space heating and cooling to homes.
Geothermal heating and cooling is a relatively new technology atypical in homes, but it is hardly inferior. In 1993, the EPA identified geothermal technology as a viable approach to reducing energy usage and pollution without sacrificing the reliability and comfort of conventional systems. With roughly 50,000 geothermal systems installed each year, geothermal systems are gaining popularity.
Geothermal heating and cooling systems, also known as ground-source heat pumps, vary in design, operation, and cost. Some systems require digging deep trenches or wells, while others use existing bodies of water. Each system type has advantages and disadvantages.
What is Geothermal Heating and Cooling?
Geothermal heating and cooling is a method of heating and cooling indoor spaces by exchanging heat with the ground. In some cases, geothermal heating is also used for heating water. Several types of geothermal heat pumps exist.
How Does a Geothermal Heat Pump Work?
Geothermal heat pumps capitalize on the consistent temperatures found a few feet below the ground’s surface. According to Energy.gov, underground temperatures can range from 45 to 75 degrees Fahrenheit, depending on latitude.
The electricity-powered heat pump circulates a fluid through underground pipes to move heat indoors or outdoors. Water, refrigerant, or a blend of water, refrigerant, and antifreeze are fluids used to transfer heat. A heat pump moves ground heat indoors when it’s cold outside and heat from the house to the ground if it’s warm outside.
Heating Mode Operation: Heat from the ground is delivered to the house.
The heat pump, located above ground, circulates fluid through buried pipes.
The fluid absorbs heat from the ground as it moves through the pipes’ loops.
The heated fluid travels to the house and transfers heat to the HVAC system for space heating or the desuperheater for water heating.
The fluid circulates back underground to absorb more heat.
Cooling Mode Operation: Heat from the house is delivered to the ground.
- The fluid absorbs heat from the air inside the house through the HVAC system.
- The heat pump circulates the fluid to the buried pipes.
The ground absorbs the fluid’s heat as it moves through the pipes.
The fluid circulates back to the house to absorb more heat.
Types of Geothermal Heating and Cooling Systems
Most geothermal heating systems are categorized as closed-loop or open-loop. One additional category is the hybrid system.
Closed-loop systems circulate a fluid mixture containing antifreeze through a closed or sealed loop of polyethylene pipes buried underground or submerged in water. Closed-loop systems are more common than open-loop or hybrid systems.
Horizontal, vertical, and pond/lake are three closed-loop systems.
Horizontal systems are generally the most cost-effective. Installation of a horizontal system involves digging numerous trenches at least four-feet deep; the channels must be deeper than the frost line. The trenches’ length, which can be up to 400 feet long, depends on the house’s square footage.
Pipes are laid horizontally in the trenches in a zigzagging or looping pattern. The horizontal pipe system is connected to pipes entering and exiting the house from the heat pump.
Vertical systems are used where the soil is shallow, disturbance of the landscape must be avoided, or space is limited. Vertical systems are ideal for large buildings because horizontal systems would take up too much space to accommodate the buildings’ square footage.
Multiple four-inch diameter holes are drilled up to 400 feet deep and twenty- feet apart. U-shaped pipes are buried in the boreholes, grouted, and connected to horizontal lines leading to and from the building’s heat pump.
A pond/lake geothermal system exchanges heat with a body of water instead of the ground. A pond/lake system is generally the most affordable option if water is available because it incurs no drilling or digging costs. Another advantage is the easy access to the pipes if a leak or other issues occur.
Pipes run horizontally from the house to pipes coiled on racks and placed at least eight feet beneath the water’s surface or on the pond’s floor. The pipes must be deep enough to be unaffected by surface temperatures. A geothermal system can’t be used with every body of water. There are depth, volume, and quality requirements for the water.
The open-loop system is the simplest form of geothermal heating and cooling. An open-ended pipe draws water from an underground well or body of water. The water circulates to the heat pump in the house, and the spent water is returned to the source or deposited in a second well.
This system requires an adequate clean water supply and adherence to local codes and regulations. Dissolved chemicals and minerals can damage heat pumps and reduce water flow through the pipes. Some regional regulations require that output water be treated before it’s returned to the source, and some localities completely ban water discharge.
A hybrid or dual-source system combines geothermal heating with an air-source heat pump. Adding an air-source heat pump allows the ground system to be smaller and reduces the system’s overall cost. The system utilizes the air-source heat pump during peak heating and cooling times for greater efficiency.
Hybrid systems provide the benefits of geothermal systems while using less land and lowering costs. Hybrid systems are less efficient than fully geothermal systems but more efficient than air-source heat pumps alone. A hybrid system operates best where cooling needs are more significant than heating needs.
Advantages of Geothermal Heating and Cooling Systems
Geothermal heating and cooling systems are praised for their many advantages over conventional approaches.
Lower Operating Costs
Geothermal systems are powered by electricity and have lower operating costs than conventional HVAC systems. According to the Department of Energy, geothermal systems can be 300 - 600% efficient, even on the coldest days. Additionally, ground-source heat pumps are more efficient than air-source heat pumps, consuming 25 - 50% less energy.
Clean Renewable Energy
Geothermal systems use a clean, renewable energy source–the earth’s natural heat. Geothermal heat does not produce emissions or deplete natural resources. The Department of Energy and the Environmental Protection Agency recognizes geothermal systems as energy efficient and environmentally friendly.
While geothermal heat is a renewable resource, ground-source heat pumps are powered by electricity from non-renewable fossil fuels.
Geothermal systems are low-maintenance due to few moving parts and protection from the elements. In contrast, furnaces require regular maintenance and yearly inspections.
Heat pump life expectancy is 20 -25 years. The life expectancy of a ground loop system is more than 50 years, significantly more time than how long a furnace lasts.
Disadvantages of Geothermal Heating and Cooling
Geothermal systems have few disadvantages, yet the drawbacks are significant.
Geothermal systems have much higher upfront costs than other systems. Geothermal system installation can run from $15,000 to $50,000, depending on the system's type, complexity, and modifications made to the house’s existing heating system.
Geothermal heating requires skilled professionals to design and install the systems. As a relatively new technology, the amount of qualified installers is limited, and a lack of competition drives up the price.
Installation of a geothermal system is site dependent. In other words, geothermal systems are designed and sized exclusively for each location. Some properties can’t accommodate a geothermal system because of space constraints or local regulations. Installation is disruptive to the landscape. Furthermore, heavy equipment for digging and drilling must be brought on-site, causing further disruptions.
Geothermal heating and cooling is a new alternative to conventional HVAC systems and has a much potential. Geothermal systems’ dependence on the earth’s heat as opposed to fossil fuels provides homeowners with a long-lasting, low-maintenance HVAC system and energy savings while reducing the homeowners’ carbon footprint.
Installation of a geothermal system is only possible for some homes because installation is quite expensive, and some pieces of land can't accommodate it. Installation of a geothermal heating system is more attainable if you can take advantage of tax incentives, install a pond/lake system, and plan to stay in your home long enough to recoup the costs over time through energy savings.
Frequently Asked Questions
Is geothermal worth it?
Geothermal heating and cooling systems are significantly more expensive than alternative systems, but the additional money can be recouped over time through energy savings. Depending on installation costs, energy costs, and other factors, it could take five to ten years to see a return on the investment.
Are geothermal heat pumps expensive?
According to HomeGuide, geothermal systems cost, on average, $15,000 - $35,000 to install. Some of the installation costs can be offset by a tax credit provided by The Inflation Reduction Act of 2022. Homeowners who install geothermal heating systems between 2022 and 2033 are eligible for up to 30% credit.
Does geothermal heating work in cold climates?
Unlike air-source heat pumps, geothermal heat pumps are appropriate for cold climates because the ground’s internal temperature is unaffected by surface temperatures.