Geothermal Heating and Cooling
True geothermal power
occurs naturally in the form
of hot springs and geysers -
think Old Faithful.
The modern day
geothermal heating and
cooling system, invented in
Pennsylvania in 1945, takes
advantage of the constant
available six feet or more
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 cooling applications.
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 cooling Btus.
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
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 to dehumidify.
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
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
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.