Ever live in an apartment with the utilities included for free? Well, geothermal is sort of like that – the earth provides free home heating and cooling for anyone who wants it. And the systems to capture it are cheaper and more efficient than ever. So read on to learn more about geothermal home heating and cooling, and how it can drastically cut your energy consumption and utility bills.
How Does Geothermal Heating / Cooling Work?
Lots of terms refer to geothermal heating and cooling: geothermal exchange, geoexchange, geothermal heat pumps, ground source heating, earth energy… but the principle is always the same. In a nutshell, geothermal heating & cooling take advantage of the steady temperatures just below the earth’s surface to raise or lower the temperature in your home. Underground temperatures remains constant all year round, usually around 50-60 degrees F (depending where you live). Pipes circulate liquid from above ground to below ground, bringing warmth up into your home in the wintertime and cooler temperatures up in the summer.
This means if it’s 20 degrees outside, your heating system doesn’t need to artificially warm air all the way from 20 degrees, since the “starting point” is already much closer to the desired indoor temperature. And summertime air conditioning can take advantage of the geothermal system instead of working to chill that hot outdoor air.
Technically speaking, thermodynamics state that heat always wants to move towards cold. So geothermal cooling is actually the “dumping” of excess heat underground, as opposed to the cooling of air in your home. But the end result is a nice cool house, so you get the idea.
What Equipment is Used for Home Geothermal Heating & Cooling?
Geothermal systems circulate liquid (usually glycol- or alcohol-based antifreeze solutions) through pipes in the ground to transfer heat. Usually these are “closed loop” systems where the liquid is warmed (or cooled) as it passes underground and then flows back to the home. Less common are “open loop” systems where underground water from an aquifer is pumped into the home, and then discharged back underground after use.
An average 2,000-square-foot home might require 1,500 to 1,800 feet of pipe to circulate the liquid. Depending on factors like soil conditions and local climate, closed loop systems may be laid out horizontally at a shallow depth or drilled vertically deep into the ground.
Inside the home, a heat pump uses a standard cycle of evaporation, compression, condensation, and expansion. A geothermal heat pump is so efficient because it simply circulates fluid instead of using a fan to force air over compressor coils, and because the temperature differential is much greater compared to the outside air.
An air handler moves the heated or cooled air around your home just as with any other HVAC setup, and geothermal systems can be easily integrated with modern climate control systems like the Nest Learning Thermostat.
How Much Money & Energy Does Residential Geothermal Save?
A ton. Geothermal setups have the lowest life-cycle costs of any HVAC system, and reduce energy usage (and utility bills) by 25-70%. Geothermal is 50% more efficient than the best gas furnaces, and delivers double the efficiency compared to the best air conditioners. The EPA describes geothermal systems as “the most energy-efficient, environmentally clean, and cost-effective space conditioning systems available today”, and a recent Air Force Institute study found that they typically pay for themselves within 7-8 years.
Besides reducing your energy bills, they save money in other ways too. Geothermal systems qualify for a wide range of energy efficiency tax incentives and utility credits. They also add valuable equity to your home: according to the National Association of Realtors Appraisal Journal, every $1 reduction in utility bills equates to a $10-$25 increase in home value.
Learn More About Geothermal
If you’re thinking about investing in a geothermal system, a great resource for homeowners is Residential Geothermal Systems: Heating and Cooling Using the Ground Below by John Stojanowski.
Another excellent source of information is the Geothermal Exchange Organization (GEO), a non-profit trade organization. Visit the GEO website to learn more: http://www.geoexchange.org
(diagrams from Geothermal Exchange Organization)