Workers lay geothermal coils in an underground trench.

Workers lay geothermal coils in an underground trench. Credit: Getty Images / BanksPhotos

A geothermal HVAC system uses the 55-degree thermal energy in aquifers to heat and cool a house. The equipment often runs on the clean, renewable electricity generated by solar roof panels. With such a combination of technologies, a homeowner’s monthly electric bill can plunge to near zero.

Installing a geothermal HVAC system is easier if you’re in the planning stages of a major renovation or building a new home, construction contractors and heating experts say. This is because an installation can be impractical in structures that require extensive conversion for retrofitting. It is critical to employ an experienced geothermal HVAC contractor who has a track record of successful geothermal installations. Ask for licensing information, references (your architect, for example) and Better Business Bureau reports. Here’s a primer:


Groundwater at its cozy 55-degree average temperature must be brought into the geothermal system, processed and then returned underground. For this initial procedure, installers have two choices. On Long Island, where abundant, clean groundwater is usually available, two wells (called an “open loop”) are drilled 50 feet apart to bring groundwater up from and return it to the aquifer.

If soil and water conditions at the site are not suitable, a “ground or closed loop” system is the alternative. Closed loop systems may require more costly drilling. They make up less than 25 percent of Long Island geothermal systems, and they are used only when site conditions — such as contamination from sea water — eliminates the possibility of using an open loop system. It’s not up to the customer, according to J.P. Clejan, a technology executive with PGI Geothermal in Roslyn Heights. Once the loop is installed, it’s filled once with about 70 gallons of water and antifreeze solution, which remains in the closed loop to heat and cool the house.

Either way, the water is piped through a metal cabinet called a heat pump, which is installed in the basement and is about the size of a refrigerator. The heat pump extracts and boosts the Earth’s warm water temperatures high enough to heat structures, usually through forced air ducts. The procedure can be reversed to provide efficient air-conditioning.


Installing a geothermal system can cost 30 percent to 50 percent more than conventional heating and cooling systems, and they start at about $50,000. Because each project is different, the costs will vary depending on size, materials, site conditions and budget. The return on investment over the long term can be an incentive. Clejan, of PGI Geothermal, says the cost can be recouped in as little as four years due to geothermal’s lower operating and maintenance costs.

PSEG Long Island offers a discounted electric delivery rate during winter for customers who use electricity to heat their homes — including those who have geothermal systems that are not connected to solar panels but use electricity supplied by the utility, says Michael Voltz, director of Energy Efficiency and Renewables at PSEG LI, which provides rebates for geothermal heating and cooling systems because they are considered the most efficient method of air conditioning and reduce greenhouse gas emissions compared to heating with oil. “The average customer can expect a rebate for about $6,000 to $10,000 from PSEG, depending on the system’s size and energy efficiency rating,” he says.

Ronkonkoma resident Chris Jamsky says that in 2007, heating oil for her five-bedroom house was setting her back $1,600 every six weeks. She invested in a $50,000 geothermal HVAC system, which reached its payback (the difference between what a new conventional system would have cost and her geothermal cost) in seven years. Her current monthly electric bill is about $300 for heating, air-conditioning, lighting and cooking. Jamsky now says, “I’m sorry now that I didn’t go for solar panels as well — even though my all-electric house qualifies for a lower PSEG rate — my monthly bill would be much less, and I would have reached payback in only three to four years.”


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