If the home you are buying or living in has a geothermal heat pump, you have one of the most efficient heating and cooling systems available. You also have a system that works quite differently from the furnace and air conditioner most homes in our area use. Knowing how a geothermal heat pump works, what it needs, and what to ask about will help you get the most out of it.
This guide covers how the system works, the main types of ground loops, what to expect in a Fargo-Moorhead winter, routine care, and what it means when we find a geothermal system during a home inspection.
How a geothermal heat pump works
A few feet below the surface, the ground stays at a fairly steady temperature all year. The U.S. Department of Energy puts the shallow-earth range at about 40°F to 70°F, and the Minnesota Department of Health gives 40°F to 50°F at a depth of 50 feet in Minnesota. That is warmer than our winter air and cooler than our summer air.
A geothermal heat pump (also called a ground-source heat pump) uses that steady temperature. Instead of making heat by burning fuel, it moves heat:
- In winter, fluid circulating through pipes buried in the ground picks up heat from the earth. The heat pump concentrates that heat and delivers it to the house.
- In summer, the process runs in reverse. Heat is pulled out of the house and sent back into the ground.
The system has three main parts: the ground loop (the buried piping), the indoor heat pump unit, and the distribution system, usually ductwork, though some systems heat water for in-floor heat. Many units also have a desuperheater, which uses extra heat from the system to help warm domestic hot water.
Types of ground loops
The Department of Energy describes four basic loop types:
| Loop type | How it is installed | Notes |
|---|---|---|
| Horizontal (closed) | Pipe laid in trenches at least 4 feet deep | Generally the most cost-effective for homes with enough yard |
| Vertical (closed) | Holes drilled roughly 100 to 400 feet deep | Used where land is limited; Minnesota bores are commonly 150 to 200 feet |
| Pond or lake (closed) | Coiled pipe placed in a body of water | In cold climates, coils sit at least 8 feet below the surface to prevent freezing |
| Open loop | Uses well or surface water directly, then returns it | Depends on water supply and local rules |
Closed loops circulate water or a water and antifreeze mix through sealed plastic piping. In Minnesota, the Department of Health regulates drilled closed loops and open-loop systems. A drilled loop needs an MDH construction permit and a licensed contractor, and the heat transfer fluid must be an approved propylene glycol or ethanol product, to protect groundwater if a leak ever occurs. Check with local and state authorities on the North Dakota side for current requirements.
Efficiency, cost and lifespan
Geothermal systems are efficient because moving heat takes far less energy than making it. ENERGY STAR reports that certified geothermal heat pumps use 61 percent less energy than a standard model. The Department of Energy notes they are quieter than air-source heat pumps, need little maintenance, and do not depend on outdoor air temperature.
The tradeoff is cost. The Department of Energy says installation can cost several times as much as an air-source system of the same size, with the extra cost often returned in energy savings in 5 to 10 years, depending on energy prices and incentives.
Lifespan is a strong point. The Department of Energy estimates up to 24 years for the indoor components and 50 years or more for the ground loop. When buying a home, the age of the indoor unit matters most, since the loop usually outlasts several units.
Geothermal heat pumps in a Fargo-Moorhead winter
Because the loop draws on ground temperature rather than outdoor air, a properly designed geothermal heat pump keeps working through our coldest weeks. Most systems in cold climates still include supplemental (auxiliary) electric heat for the coldest days and for quick recovery.
A few things are worth knowing:
- Big thermostat setbacks can trigger backup heat. Manufacturer Enertech notes that when a thermostat recovers from a deep setback, the backup heat may come on, which raises electric costs.
- An undersized or poorly designed loop shows up in winter. If the fluid coming in from the ground runs too cold, the system loses capacity, leans on backup heat, or trips a safety switch.
- A well-insulated, well-sealed house makes any heat pump work better, and geothermal is no exception.
Routine care
Geothermal systems need less maintenance than most, but not none:
- Change or clean the air filter on the schedule in the owner’s manual. A dirty filter can cause short cycling and strain the equipment.
- Schedule a yearly service visit with a qualified geothermal or HVAC technician. A technician can check loop pressure and flow, the condensate drain, coils, electrical parts and the desuperheater.
- Keep supply and return vents open and clear.
- Watch for warning signs, such as backup heat running often in mild weather, frequent safety trips, water around the unit, or a drop in comfort.
- Keep the paperwork. Loop design, installation records and service history are valuable to you and to a future buyer.
What it means when we find a geothermal system during an inspection
During a home inspection, we look at the visible parts of a geothermal system: the indoor unit, its operation in normal mode, the visible piping and connections, the condensate drain, filters and ductwork, and signs of leaks or past problems. We also note the unit’s data plate so you know its age.
Geothermal systems are more complex than the furnaces and air conditioners we usually see, and fully evaluating one takes specialized training and equipment. Most of the system, including the ground loop, is buried and cannot be seen. For that reason, when we find a geothermal heat pump, we recommend having it evaluated by a licensed geothermal or HVAC professional, ideally before closing when you are buying the home.
Ask the seller for installation records, loop type and size, service history, and any warranty information. A home buyer’s inspection is a good first look at the whole house, and a homeowner inspection can help if you already own the home and want a fresh set of eyes on it. For other heating equipment, see our post on furnace disconnect switches.
Geothermal heat pump: common questions
Does a geothermal heat pump work in North Dakota winters?
Yes. It draws heat from the ground, which stays far warmer than winter air. Most cold-climate systems also have auxiliary electric heat for the coldest days.
How long does a geothermal system last?
The Department of Energy estimates up to 24 years for the indoor unit and 50 years or more for the ground loop.
What maintenance does a geothermal heat pump need?
Regular filter changes by the homeowner, plus a yearly service visit by a qualified technician to check loop pressure, flow, drains and controls.
Is a geothermal heat pump the same as geothermal energy from hot springs?
No. A home geothermal heat pump uses the mild, steady temperature of the ground near the surface. It does not tap deep underground heat.
Sources
- U.S. Department of Energy, Energy Saver. Geothermal Heat Pumps.
- ENERGY STAR. Geothermal Heat Pumps and Geothermal Heat Pumps Key Product Criteria.
- Minnesota Department of Health. Geothermal Heating and Cooling Systems (updated October 2024).
- Enertech Global. Geothermal Best Practices for Cold Weather Performance (2021).
- ACHR News. Geothermal Service Is Simple and Straightforward (2017).