VERONA, Wis. -- Area heating and cooling companies said a 30 percent federal tax credit for geothermal systems has many looking to install a system -- including homeowners.

Those homeowners are digging deep into their pockets -- and the earth -- in hopes of reaping big rewards.

At a Verona house in a quiet subdivision, a truck was parked in the backyard and a 50-foot well-drilling machine was pumping away Friday.

Neighbors looking in from the outside might think it looks like crews are drilling a well -- and it sounds like it.

At the home, crews are using a regular well-digger to drill down 150 feet, and there's a lot of mud and water in the drill area.

But the homeowner said they are not digging a private well but several 4-inch-wide holes. They will eventually hold special liquid-filled tubing that will be connected to the house.

It's all aimed at harnessing the warm earth below -- where it's always 55 degrees.

"The earth is nothing but a great big solar panel," said Stan Olson, owner of Olson Heating and Cooling in Mount Horeb.

The warm soil is also a source of free or low-cost energy. For homeowner Cathy Bishell that means "hopefully free heat," she said, laughing.

Bishell is buying a roughly $30,000 geothermal heating and cooling system.

She said she has the information, the Department of Natural Resources permit and the knowledge that geothermal isn't just for businesses; it's for homes, too.

"I jumped on board right away -- the minute I found out it could be done," Bishell said.

Bishell contacted Olson, and he told her about the 30 percent federal tax credit for such systems that was included in the last energy budget bill passed in Washington, D.C.

Now, using that credit, Bishell and a lot of other homeowners are investing in it.

Oh, wow -- it's gotten be 10 fold since the 30 percent tax credit's come out," Olson said.

Olson's company is installing geothermal systems on big and small city lots alike, because systems can go vertically down into small areas as well as horizontally.

The so-called "closed loop" system doesn't tap the aquifer and holds huge benefits, he said.

Geothermal energy, which uses a heat pump instead of furnace or air conditioner, can start saving money for homeowners in as few as four years, according to Olson.

"Once that initial investment is made, the customer will have a great payback, and over a 20-year span they're going to save tens of thousands of dollars," Olson said.

He said it can take as long as 10 years for homeowners to break even and start reaping the savings. He said it all depends on whether the furnace and central air need replacing anyway -- geothermal doesn't use either.

Homeowners do have to pay more for electricity to run the heat pump, but Olson said that in the long run geothermal is still vastly more efficient than natural gas.