What makes a heat pump geothermal instead of air-source

A geothermal heat pump pulls heat from the ground or groundwater instead of from the air. An air-source heat pump pulls it from outside air. The difference is in where the outdoor unit sits and what it connects to. If your outdoor equipment is buried underground or connected to a well, you have geothermal. If it sits on your roof, wall, or ground level as a visible box, you have air-source.

Geothermal systems cost more to install because they require digging or drilling. Air-source systems are cheaper upfront and more common in most climates. Both heat your home in winter and cool it in summer, but geothermal runs more efficiently because ground temperature stays stable year-round, while air temperature swings wildly.

The easiest way to know which you have is to look outside. If you see a large metal box or boxes near your home, you have air-source. If you see nothing but pipes coming out of the ground, or if your installer told you they drilled a well, you have geothermal.

Key Takeaways

  • Geothermal systems have underground loops or wells; air-source systems have visible outdoor units that look like air conditioners.
  • Geothermal costs more to install but runs more efficiently because ground temperature is stable, while air temperature changes with seasons.
  • Your paperwork from installation will state which type you have, and your installer can confirm in one phone call.
  • Both types use the same indoor equipment and controls, so the difference is entirely in what sits outside.

Where the outdoor equipment is located

Air-source heat pumps have a visible outdoor unit that looks similar to an air conditioner. It is usually mounted on the ground next to your home, on a wall, or on the roof. The unit contains a fan and coils and is typically 2 to 4 feet tall and 2 to 3 feet wide. You can hear it running, especially in winter when it works harder.

Geothermal systems hide their outdoor equipment underground. Instead of a box, you see either a series of pipes coming up from the ground (called a vertical loop system) or nothing at all if the pipes run horizontally under your yard. Some geothermal systems use a well, in which case you might see a small pump house or just a capped pipe. If your installer dug trenches across your yard years ago, that was the sign of geothermal installation.

If you moved into your home and are unsure, check your utility bills or installation paperwork. The paperwork will name the system type and the manufacturer. If you cannot find it, call the HVAC contractor who installed it or services it now — they can tell you in seconds.

What your installation paperwork says

Your installation invoice or warranty paperwork will state the system type clearly. Look for language like "ground-source heat pump," "closed-loop geothermal," "open-loop geothermal," or "air-source heat pump." The manufacturer name and model number will also indicate the type — geothermal manufacturers include WaterFurnace, Climatemaster, and Bosch; air-source makers include Daikin, Fujitsu, and Lennox.

If you do not have the original paperwork, contact the HVAC company that installed the system. They keep records by address and can email you a copy or tell you over the phone. If the original installer is out of business, any HVAC contractor can look at your system and identify it within minutes.

The cost difference between the two types

Geothermal systems cost between $15,000 and $30,000 installed, depending on how deep the ground loops need to go and how much digging your yard requires. Air-source systems cost between $8,000 and $15,000 installed. The higher upfront cost of geothermal is offset by lower operating costs — geothermal systems use 25 to 50 percent less electricity than air-source systems in most climates.

Over 15 to 20 years, geothermal often costs less to run, but the payback period depends on your local electricity rates and how cold your winters are. In very cold climates, geothermal saves more money. In mild climates, air-source may never pay back its lower installation cost through energy savings alone.

If you are trying to decide which to install, the ground conditions on your property matter most. Geothermal requires either space to dig trenches or permission to drill a well. If your lot is small, rocky, or has a high water table, geothermal may not be practical, and air-source is your only option.

How to check your outdoor unit in person

Walk around the outside of your home and look for any large metal box or cylinder. Air-source units are obvious — they look like window air conditioners scaled up. They have a fan grille on top or the side, and you can see refrigerant lines running from the unit into your home. The unit will have a manufacturer label with a brand name and model number.

If you see no outdoor unit at all, look for pipes or conduit coming out of the ground. Geothermal systems often have a small access point or valve box near the foundation. You might also see a ground loop running under your yard if the installer used a horizontal loop instead of drilling vertically. If your yard has a small building or shed near the house, it might contain the geothermal pump and controls.

Take a photo of any outdoor equipment and the manufacturer label. If you call an HVAC contractor later, the photo will help them confirm the system type and answer questions about maintenance or repair.

Why the difference matters for maintenance and repair

Geothermal and air-source systems need different maintenance. Air-source units need the outdoor coils cleaned regularly because they collect dust and pollen from the air. Geothermal systems need periodic checks of the ground loop fluid to may support it is not leaking and the pump is circulating properly. Both types need the indoor air filter changed every 1 to 3 months.

If your system breaks down, the repair cost and time depend on which type you have. Air-source repairs are usually faster because the technician can access the outdoor unit easily. Geothermal repairs sometimes require digging or drilling if the problem is in the ground loop, which takes longer and costs more. However, geothermal systems break down less often because they have fewer moving parts exposed to weather.

Knowing which type you have helps you plan for maintenance costs and understand what to expect when you call for service. Tell the contractor upfront whether you have geothermal or air-source so they bring the right tools and parts.

Frequently Asked Questions

Can I convert an air-source heat pump to geothermal?

No, conversion is not practical. You would need to dig or drill, install new ground loops, and replace the outdoor unit and much of the indoor piping. The cost is nearly the same as installing a new geothermal system from scratch, so most homeowners straightforward replace the air-source unit when it fails.

Do geothermal systems work in cold climates?

Yes, geothermal systems work in very cold climates and often work better than air-source systems because ground temperature stays above freezing even when air temperature drops far below zero. Air-source systems lose efficiency in extreme cold and may need a backup heating source. Geothermal is common in Minnesota, Wisconsin, and other cold states.

What if I see two outdoor units?

Two air-source units usually mean you have a multi-zone system that heats or cools different parts of your home separately. Two geothermal units are less common but can happen in large homes. Check the paperwork or call your installer to confirm. If one unit is much older than the other, you may have replaced one system without replacing the other.

How long do geothermal systems last?

Geothermal ground loops last 25 to 50 years because they are buried and protected from weather. The pump and indoor components last 15 to 25 years, similar to air-source systems. Air-source outdoor units typically last 10 to 15 years because they are exposed to sun, rain, and temperature swings.