Efficiency and Environmental Benefits

According to the Environmental Protection Agency, Geothermal ground source heat pump systems are one of the most energy efficient, environmentally clean, and cost-effective space conditioning systems available. About 70 percent of the energy used by a geothermal heat pump system comes in the form of renewable energy from the ground.   High-efficiency geothermal systems are on average 48 percent more efficient than gas furnaces, 75 percent more efficient than oil furnaces, and 43 percent more efficient when in the cooling mode [1].
 
Since a geothermal heat pump system burns no fossil fuel on-site to produce heat, it generates far fewer greenhouse gas emissions than a conventional furnace, and completely eliminates a potential source of poisonous carbon monoxide within the home or building. Even factoring in its share of the emissions from the power plant that produces electricity to operate a geothermal heat pump system, total emissions are far lower than for conventional systems.

How is Efficiency Measured?

All heating and cooling systems have a rated efficiency from a U.S. governmental agency. Fossil fuel furnaces have a percentage efficiency rating. Natural gas, propane and fuel oil furnaces have efficiency ratings based on laboratory conditions. To get an accurate installed efficiency rating, factors such as flue gas heat losses and cycling losses caused by oversizing, blower fan electrical usage, etc., must be included.

Geothermal heat pumps, as well as all other types of heat pumps, have efficiencies rated according to their coefficient of performance or COP. It's a scientific way of determining how much energy the system produces versus how much it uses. Most geothermal heat pump systems have COPs of 3-4.5. That means for every unit of energy used to power the system, 3-4.5 units are supplied as heat. Where a fossil fuel furnace may be 78-90 percent efficient, a geothermal heat pump is about 400 percent efficient. Some geothermal heat pump manufacturers and electric utilities use computers to accurately determine the operating efficiency of a system for your home or building.

Figure Courtesy of Waterfurnace

Table comparing heating and cooling efficiencies of geothermal heat pumps with conventional systems.
Figure Courtesy of Waterfurnace

Environmental Benefits

According to data supplied by the U.S. Department of Energy (DOE) Office of Geothermal Technologies, nearly 40% of all U.S. emissions of carbon dioxide are the result of heating, cooling, and hot water systems in residential and commercial buildings.  This is roughly equivalent to the amount of carbon dioxide contributed by automobiles and public transportation [2]. 

Because geothermal pump heating systems do not burn fossil fuels for heat production, they generate far fewer greenhouse gas emissions than a conventional furnace. They also provide higher air quality because there are no emissions of carbon monoxide.  In general, a 3-ton residential geothermal heat pump system produces an average of about one pound less carbon dioxide per hour compared to a conventional system. Over an average 20-year lifespan, installation of 100,000 units of residential geothermal systems can reduce greenhouse gas emissions by almost 1.1 million metric tons of carbon equivalents [3]. That would be the equivalent of removing 58,700 cars from our highways or planting more than 120,000 acres of trees.

Building Energy Use Statistics

Buildings represent 38.9% of U.S. primary energy use (includes fuel input for production) [4].

Buildings are one of the heaviest consumers of natural resources and account for a significant portion of the greenhouse gas emissions that affect climate change. In the U.S., buildings account for 38% of all CO2 emissions [5].

Buildings represent 72% of U.S electricity consumption [4].

Sources

1. Agency, E.P., Space Conditioning: The Next Frontier. 1993.
2. National Renewable Energy Lab, D., Office of Geothermal Technologies, Environmental and Energy Benefits of Geothermal Heat Pumps. 1998.
3. Consortium, G.H.P., Commonly Asked Questions about an Uncommonly Sound Technology. 2008.
4. Environmental Information Administration (2008). EIA Annual Energy Outlook.
5. Energy Information Administration (2008). Assumptions to the Annual Energy Outlook

How Geothermal Heat Pumps Work
Types of Ground Loops
Installation and Cost