Geothermal is a broad term, meaning using heat from the earth. GAHT systems do use the stable temperatures of the soil, however they are very different systems than geothermal heat pumps, often called geothermal systems for short. A geothermal heat pump incorporates a refrigeration cycle and circulates a fluid underground. They are much more complicated and expensive systems than GAHT systems. GAHT systems, in contrast, simply circulate air and bury pipes relatively shallow, up to 4’ underground.