The Power of Dirt – Geothermal Heat Pumps

Humans have been utilizing the thermal qualities of dirt since our very beginnings. Paleolithic cavemen were, obviously, known for living in caves because they were simply the best places to live. Caves remained cool in the summer and warm during the winter due to the massive thermal storage capabilities of the surrounding earth. The sod homes of the prairie pioneers and the adobe pueblos of the southwestern pueblo Indians utilized the same basic principles of thermal mass.

However, cave-living is hardly a solution for our 21st century energy woes. Nor do many of our homes consist of thick adobe walls and earthen roofs. For the most part, and into the foreseeable future, we continue to live in relatively flimsy boxes atop the earth. However, that doesn’t mean that we can’t take advantage of the immense thermal potential of the earth directly below.

How It Works

Geothermal systems used in eco-friendly homes today, known as geothermal or ground source heat pumps, try to take advantage of the seasonally moderate temperatures underground using the earth as a heat source during the winter and a heat sink during the summer. Typically this involves sinking a series of water-carrying tubes 250 to 300 feet below the surface to dissipate heat generated by the compression of refrigerant. In comparison, an air source unit attempts to cool the compressor by blowing ambient outside air over it.


Ground source heat pumps are characterized by high capital costs and low operational costs compared to other HVAC systems. The US Department of Energy puts the price of a new ground source heat pump system at $7500. In comparison homeowners can expect to pay about $5000 for traditional HVAC systems. However, while the NAHB estimates a typical HVAC system will last between 10-15 years before needing replacement of key components or substantial repair, geothermal loop fields are expected to last at least 50 to 200 hundred years. Maintenance costs are also between one-fifth and one-half the cost of traditional HVAC systems which is positively dirt-cheap. Perhaps even more enticing are the substantial subsidies offered by all levels of government and even electrical companies.

Yes, the dirt beneath your feet is a valuable asset being used by millions to help heat and cool their homes. Geothermal heat pumps operate two times more efficiently, cost significantly less to maintain, and can be a smart long-term investment. When considering a zero-energy home, ground source geothermal is a key approach to minimizing the energy load requirements.