We got a call last week for a home inspection at a vandalized foreclosure. The buyer told us we weren’t going to be able to test the air conditioning system because he noticed that the outdoor unit (condenser) had been stolen. When we got to house, sure enough, there was no condenser unit outside—but not because it had been stolen. The home had a geothermal heat pump system. 

    Unlike a regular split-system heat pump, geothermals do not need to have an outdoor unit and the system (shown in the photo above) was fully functional. Most geothermal heat pumps we encounter are “package units,” with both the condenser and air handler in one large cabinet inside the home. But we have come across geothermals that are setup as split systems, with both an outdoor and indoor unit, with refrigerant piping connecting them.

   We only get to see a geothermal system two or three times a year because they are so rare. Most folks aren’t familiar with this alternative to the regular heat pumps that use outdoor air to collect or dissipate heat. Geothermals (also called ground source heat pumps) utilize the steady cool temperature of the earth a few feet below the surface for heating and cooling—and, in some units, also for making hot water. 

   Electricity circulates liquid, typically just ordinary water, through a closed loop of piping in the ground to dissipate (cooling mode) or absorb (heating mode) heat in the soil. Geothermals are 20% to 50% more energy-efficient that regular heat pumps. So, why aren’t they wildly popular? Initial cost is the main reason: $15,000 to $20,000 to install the indoor unit and the 1,500 to 1,800 lineal feet of underground pipe necessary for the system to operate efficiently.

   Most of the geothermal systems we inspect are 25 to 35 years old, and still operating satisfactorily because of their simplicity compared to an air-based heat pump. They were more popular during the 1970s and 80s, when the energy crunch made people keenly aware of the benefits of using the earth as an energy source.

   The most popular manufacturer in our area is Florida Heat Pump (www.fhp-mfg.com), and for more general information about ground source heat pumps we suggest visiting the International Ground Source Heat Pump Association’s website (www.igshpa.org).

    Also, see our blog posts How can I tell whether the condenser (outdoor unit) is an air conditioner or heat pump? and Does an old air conditioner use more electricity as it ages?

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  To learn more about heating and air conditioning systems, see these other blog posts:

• How can I find out the SEER of my air conditioner? 

• My air conditioner won't turn on. What's wrong? 

• How can I find out the size of my air conditioner? 

• Where is the air filter for my central air conditioner and furnace? I can’t find it? 

• How did homes stay cool in Florida before air conditioning? 

• What is wrong with an air conditioner when the air flow out of the vents is low?

• Why has the thermostat screen gone blank? 

• Why does it take so long to cool a house when an air conditioner has been off for a while? 

• Why is my air conditioner not cooling enough? 

• What are the most common problems with wall/window air conditioners?  

• Will closing doors reduce my heating and cooling costs? 

   Visit our HEATING AND AIR CONDITIONING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.