Geothermal Heat Pumps

Ten feet below the surface, the ground stays roughly 50-55 degrees F year-round across most of the continental U.S. Warmer than winter air, cooler than summer air. A ground-source heat pump exploits this stable temperature to deliver 3-5 units of heating or cooling per unit of electricity consumed.

A geothermal heat pump (also called a ground-source heat pump, GSHP) circulates fluid through buried pipes to exchange heat with the earth. In winter, the ground at 50 degrees F is warmer than outdoor air, so the heat pump extracts heat more easily and achieves a higher COP than an air-source unit fighting 10 degree F air. In summer, the ground at 55 degrees F is cooler than 95 degree F outdoor air, making it a better heat sink. The result: COPs of 3.5-5.0 year-round, compared to 1.5-2.5 for air-source heat pumps in extreme cold.

Size the advantage. Air-source heat pump at 0 degrees F outdoor: COP of about 2.0. Ground-source at the same location: COP of about 4.0, because the ground remains at 50 degrees F regardless of air temperature.

Count the cost. Horizontal ground loop (trenched at 4-6 feet): $15,000-$25,000 installed. Vertical loop (drilled 150-400 feet): $20,000-$30,000. Air-source heat pump: $3,000-$8,000.

If ground-source heat pumps are twice as efficient, why do air-source units outsell them roughly 50 to 1?

Upfront cost is the barrier. Drilling or trenching adds $10,000-$20,000+ over air-source installation. Payback runs 7-12 years. The ground loop lasts 50+ years, but most homebuyers optimize for purchase price, not lifetime operating cost.

Ground-source heat pumps matter most in cold climates where air-source COP degrades, making them central to building electrification strategies in northern states.

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