Geothermal Heating and Cooling
True geothermal power occurs
naturally in the form of hot
springs and geysers - think Old
The modern day geothermal
heating and cooling system,
invented in Pennsylvania in 1945,
takes advantage of the constant
ground temperature available six
feet or more underground.
The soil at this depth maintains a
temperature of 45 to 75 degrees
F and provides an inexhaustible
supply of non-fossil fuel for a
wide variety of heating and
The primary benefit of a geothermal system that attracts most homeowners is its
efficiency. Simply put, for every dollar you spend on kilowatts of electricity to run a ground
source heat pump, you will get back 3 to 4 times the energy equivalent in heating or
This incredible efficiency can be attributed for the most part to the heat pump. When you
look at heat pumps online you'll see them with ratings of 2.8 COP or 3.5 COP, etc. COP is
the abbreviation for Coefficient Of Performance and is based on the ratio of energy
output vs input. So a heat pump with a 3.0 COP would output 3 times more energy than
it takes in.
By comparison, the degree of efficiency achieved by other residential alternate energy
systems like solar electric and wind power is miniscule. For example, the average solar
panel is only 13% efficient while wind power fares slightly better at 25-30%.
Cost wise, the $20,000 - $40,000 spent on a geothermal system is actually less than you
would have to spend on a solar or wind system designed to replace 100% of the
electricity provided by your local utility.
Hydronic and forced air geothermal systems
A forced air geothermal system uses the duct work in your house to distribute heated air
in the winter or extract hot and humid air in the summer. The drawback to a forced air
system is its inability to "keep up" in extremely cold weather and requires a conventional
furnace as a back up.
On the other hand, a hydronic geothermal system heats your home by circulating heated
water through tubing submerged in a slab of concrete or special mortar applied over the
sub-floor. This technique works best for new construction. Alternately, the heated water
can be fed directly to baseboards or radiators to retrofit existing buildings.
The drawback with hydronic systems is their limited ability to cool. You can reduce the
temperature in your home by 10-15 degrees with a hydronic system, but it does nothing
New geothermal installations vs retrofits
If you visit any of the geothermal forums or message boards you'll quickly discover the
majority of discussions center around problems encountered during geothermal retrofits.
A good analogy would be replacing your Chevy engine with one from a Toyota. Sure, you
could get it to work, but at what cost and would the results meet your expectations?
This is not to say a professionally designed and supervised geothermal retrofit wouldn't
be the perfect solution to your heating and cooling needs.
Finding a contractor
As far as I'm concerned, the design, purchasing, and installation of the equipment for a
geothermal system is about as far away from a DIY project as you can get. I'll even take
it a step further; I wouldn't even attempt to be the contractor responsible for bringing all
the disparate parts together into one, efficient, functioning unit. Geothermal is far too
complex and encompasses too many variables to be undertaken by anyone less than an
experienced, professional designer or engineer.
A good place to start your search for a contractor is to Google "Your State geothermal
engineer or designer." Go to their websites and read what they have to say and look for
some testimonials. Once you get a list of 3 or 4 contractors, interview them just as would
a contractor for any other major construction project.
As they say, "Knowledge is power." The better you understand the workings of a
geothermal system the better prepared you'll be to interview prospective engineers and
deal with the inevitable problems that arise during a project of this scope.
Without a doubt, the reason for the recent surge in interest in geothermal is the 30%
energy tax credit. In addition, many states also offer incentives to further defray the
cost. All ENERGY STAR geothermal heat pumps automatically qualify for the Federal tax
credit and the system must be placed into service before December 31, 2016.