In the face of recent propane shortages and record high prices for the fuel - some rural areas reported deliveries as high as $8 per gallon - homeowners who rely on propane to heat their homes are beginning to consider more reliable, less costly alternatives. With increasing frequency, many are turning to geothermal, attracted by its ability to reduce heating and cooling costs by as much as 70 percent while relying on a clean, renewable and unlimited energy source.

The U.S. Environmental Protection Agency (EPA) says that geothermal heat pumps are the most energy efficient, environmentally clean and cost-effective space conditioning system available today.

In fact, according to the Geothermal Exchange Organization (GEO), calculations from a major geothermal heat pump manufacturer show that at average prices during this year's blizzards, thermal energy from the earth saves 426 percent compared to fuel oil, 81 percent compared to natural gas, and an astounding 615 percent compared to propane.

A geothermal system takes advantage of free solar energy stored just below the surface of the earth. Using a series of pipes (an earth loop) buried in the ground and a geothermal (sometimes referred to as a ground source) heat pump, the geothermal heating and cooling system extracts heat from the earth and carries it to a building in the winter.

An indoor unit compresses the heat to a higher temperature and distributes it throughout the structure. In the summer, the process reverses and the system extracts heat from the building and rejects it to the earth.

"In both cases, the geothermal system delivers consistent temperatures and efficiencies that exceed those of conventional HVAC systems, offering savings as high as 70 percent for heating, cooling and hot water," said Tim Litton, director of marketing communications at WaterFurnace International, Inc., the leading manufacturer of geothermal and water source heat pumps.

"That's because the most efficient geothermal systems can deliver an astounding five units of energy for every one unit of electrical energy used, which translates to a 500 percent efficiency rating."

A geothermal system runs more frequently than other heating and cooling systems and at lower speeds, which means the air is always circulating through the house to reduce hot and cold spots as it increases comfort levels. Constant circulation also means air inside the home regularly circulates through the air filter, improving indoor air quality (IAQ).

In addition, a geothermal system does not require combustion and therefore produces none of the products associated with combustion, including carbon monoxide, which can negatively impact the air you breathe. Nor does it require a system to vent monoxide and other dangerous exhaust gases.

"Homeowners who have installed a geothermal system will also tell you that the system is quiet," added Litton. "There are no noisy outdoor components and, best of all, no storage tanks to fill. Instead, all the equipment is located inside, conveniently sized and constructed for quiet, efficient operation."

What's more, the average lifespan of a geothermal system is 25 years, compared to 15 years for a more traditional heating and cooling system, and in many cases, earth heat exchange loops are warranted for up to 50 years.

Homeowners who install a geothermal system prior to Dec. 31, 2016, can take advantage of a federal renewable energy tax credit that offers a tax incentive of 30 percent of the installed cost of the system. This credit can be used in combination with utility rebates and state tax incentives, where available, to make geothermal systems more affordable than ever.