Comparison

Air-Source vs Ground-Source Heat Pumps

Air-source units use outdoor air. Ground-source units use a ground loop. Compare site, installation, seasonal performance and lifecycle cost.

Mechanical, HVAC & Fluids · Last reviewed October 17, 2026

Short answer: air-source units cost less and install quickly, and suit most sites. Ground-source systems cost much more up front for the ground loop, but run more efficiently and steadily, and can pay back where energy prices are high, the site allows drilling or digging, and the building will be used for decades.

	Air-source	Ground-source (geothermal)
Heat source	Outdoor air, which varies with the weather	The ground or groundwater, at a stable temperature through the year
Seasonal performance	Typical seasonal COP of about 2.5 to 4, lower on very cold days	Often about 3.5 to 5, steadier through the year
Cold-weather capacity	Falls with outdoor temperature, so backup heat may be needed	Largely unaffected by air temperature
Installation	Outdoor unit on a pad or wall, a few days of work	Boreholes or trenches for a ground loop, or wells for open systems, with heavy equipment
Site needs	Space for an outdoor unit	Land area or drilling access, suitable ground conditions and water rules
Equipment life	Outdoor unit exposed to weather, with a life of about 15 years typically	Indoor equipment lasts longer, and the ground loop can last for decades
Upfront cost	Lower	Much higher, because of the ground loop
Operating cost	Higher than ground-source in cold climates	Lower, because of the higher efficiency
Noise and appearance	Outdoor fan noise	Quiet, with no outdoor unit

How to choose

Look at the site: land area, geology, groundwater and access for drilling.
Estimate the heating and cooling loads, and the number of hours of operation per year.
Compare the seasonal performance and the energy price to get the annual cost difference.
Add the extra installed cost of the ground loop and any incentives, and work out the payback.
Plan for the long term: how long you will own the building, and loop design by a qualified designer.

Common mistakes

Undersizing the ground loop, which lets the loop temperature drift over the years.
Comparing rated efficiency at one test point with seasonal performance.
Leaving out the cost of site restoration and permits.
Assuming ground-source needs no backup in every case. Design for the load.

Related tools and labs

Calculators, labs and simulators are part of the All-Access Pass.

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Questions

How deep are the boreholes?

Vertical boreholes are often 150 to 500 ft deep, depending on the load and the ground. A horizontal loop needs more land but less drilling.

What are open-loop systems?

They draw groundwater, pass it through the heat pump, and return it. They need suitable water and local approval, and are not available everywhere.

Educational material. Examples use simplified, hypothetical inputs and are not a design, a construction document or professional engineering advice. Confirm requirements with the codes and standards adopted where the work is built and with a licensed engineer.

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