One of the hottest trends in the heating and cooling industry is actually as old as the Earth itself. In fact, it uses the Earth as a primary resource for an environmentally conscious way of making homes and buildings more comfortable.

Local heating and cooling contractors have been offering geothermal systems for years, but demand for them is increasing primarily because of the public's growing desire for economic and environmental efficiency.

"We've been offering geothermal ever since 1993," said Jim Jacobs, president of Jacobs Air Conditioning and Heating of Carbondale. "Geothermal began to really take root in the late 1980s, but more and more people are getting on board with it today because of the rising cost of energy."

Jacobs said the concept of geothermal is very simple.

"It uses a closed-loop piping system that most often is buried in the ground on your property. Fluid in the pipes exchanges heat with the ground. In the summer, it gets rid of the heat from your home by transferring it to the ground," he explained. "In the winter it takes heat from the ground and uses it to warm your home."

Shirley Henson, president of Williams Air Conditioning and Heating in Murphysboro, said that geothermal takes advantage of the earth's constant temperature.

"The loops are usually buried 5 or 6 feet below the surface in a horizontal installation or go straight down several hundred feet. The system works because the ground is at a constant temperature."

Jacobs said that the best way to understand the efficiency of geothermal is by comparing it to a traditional heat pump.

"In a traditional air-to-air system like a heat pump outside your house, the system exchanges heat with the outside ambient air temperature. So if it is 30 degrees outside, there's less heat out for it to absorb, so the heat pump needs some extra help - that's when your furnace kicks in," he said.

Jacobs said the same principle works with cooling, adding that during the summer it takes extra energy for a traditional system to cool when the outdoor temperature is in the 90s.

"The beauty of geothermal is that the ground temperature in Southern Illinois is in the 50s all year long, so the system doesn't have to work nearly as hard in the summer or in the winter."

Henson said that while the initial cost is higher because of the ground loops, the long-term savings are significant.

"The thing that is so amazing with a geothermal system compared to a traditional air-to-air system is that you can recoup the additional costs within three to five years because energy usage can go down as much as 60 percent.

"People are very, very happy with geothermal," she said. "Especially when they get their power bills."

Both contractors said one of the benefits of geothermal is that the system also can be used to pre-heat water, meaning less energy is required by the home's water heater.

"Heating water accounts for as much as 40 percent of your power bill," Hanson said. "Geothermal will cut your bills tremendously."

Janet and Mike Hanson have used a geothermal system in their rural Carbondale home for more than eight years.

"We love it," Janet Hanson said. "It's quieter, cleaner and more efficient than our previous system. It provides a comfortable, even heat. It is just wonderful."

She said lower power bills prove geothermal is energy-efficient.

"From the time we first bought our home in 1988, we've tracked our energy use every month. Since going with the geothermal, we've saved electricity and money every single month," she said.

Jacobs said that while most of the calls he gets concerning new construction are for geothermal, there is also a growing number of homeowners using geothermal as a part of remodeling.

"Upgrading to a geothermal system is becoming more popular all of the time. Customers can see the savings," he said.

The U.S. Department of Energy estimates more than 1 million homes use geothermal systems, but a growing number of businesses and institutions are also choosing the systems for their efficiency. Grand Avenue Christian Church in Carbondale and Southern Illinois University's Morris Library storage facility on McLafferty Road both use geothermal systems.

The SIU building is one of the largest structures heated and cooled using a geothermal system in downstate Illinois.

Jacobs said regardless of the size of the structure, there are additional incentives to installing a geothermal system.

"Part of the federal government's recent economic stimulus package includes a tax credit on the installation of geothermal of up to $2,000," he said.

With or without tax credits, Hanson said she's a huge fan of geothermal.

"I just don't understand why everyone doesn't use geothermal," she said. "I tell everyone to do it."