Technical Comparison

Comparing geothermal heat pump technology to conventional methods of heating can be complex and multifaceted. There are no other devices that combine the heating and air conditioning features of a single heat pump, and therefore there is no direct comparison with a heat pump’s dual functions and passive domestic hot water heating.

A heat pump moves more heat energy than the electric energy it consumes, and therefore the total energy output is much greater than the electricity input.  The coefficient of performance (COP) is a value that reflects the heating efficiency of a heat pump and is determined by dividing the energy output of the heat pump by the electrical energy required to run the heat pump at a specific temperature.  The number can be compared to the steady-state efficiency of oil- and gas-fired furnaces.   Traditional combustion furnaces and electric heaters can never exceed 100% efficiency, but heat pumps "produce" extra energy by extracting it from the ground.  

In addition to the COP, a heat pump’s cooling efficiency is measured in terms of the energy efficiency rating (EER). The EER is calculated by dividing the cooling capacity of the heat pump in Btu/h by the electrical energy input in watts at a specific temperature. The cooling portion can be measured against a stand-alone air conditioning unit, which has a maximum EER of 11.7.

Ground-water or open-well geothermal applications have heating COP ratings ranging from 3.6 to 5.2, and cooling EER ratings between 16.2 and 31.1 (see Figure 9). Closed-loop applications have heating COP ratings between 3.1 and 4.9, while EER ratings range from 13.4 to 25.8 (See figure 10). Note in both figures, the component affecting the COP and EER values is the compressor. The higher the value of both the COP and EER, the more efficient the unit is.

Figure 1: Open System Earth-Energy System Efficiency (at an entering water temperature of 10°C)

Note: Indicated values represent the range of all available equipment

Figure 2: Closed-Loop Earth-Energy System Efficiency (at an entering antifreeze temperature of 0°C)

Note: Indicated values represent the range of all available equipment

Keep in mind that performance is influenced by numerous components of a system, including the soil conditions, the ground-coupled heat exchanger, the heat pump appliance, and the building distribution. Efficiency is also highly influenced by the type of compressor within the unit. Regardless, the efficiency levels of a heat pump in the appropriate design conditions far exceed traditional heating and cooling methods.

Another important element to consider in a technical comparison is the effects of energy production and consumption on prevalent environmental problems. Exploration for and extraction of fossil fuels in fragile ecosystems, spills and leaks during transportation, urban smog, acid rain and climate change can all adversely affect our environment. No form of energy is completely harmless, but some sources can have a relatively low impact. Heating your home can affect the environment in various ways, whether from gases leaving the chimney, emissions at coal- or gas-fired electricity-generating stations, or flooding at a remote hydroelectric site. In regards to overall environmental impact, geothermal technology presents a clean and relatively harmless alternative.

Natural Resources Canada recognizes there is no easy solution when it comes to comparing heating and cooling systems, as comparisons are home and situation specific. However, each home can make a major contribution to reducing energy use and subsequently encouraging environmental sustainability.

Sources

“An Introduction to Residential Earth Energy Systems.” Natural Resources Canada publication, 2005.

“Comprehensive Energy Use Database Tables.”  Natural Resources Canada, Office of Energy Efficiency Website. 

“Earth Energy” Website.

“Earth Energy, Ground Source/Geothermal Heat Pumps, Geoexchange.” Natural Resources Canada, 2005.

“Energy efficiency regulations–labeling, rating and certification.” Natural Resources Canada, Office of Energy Efficiency Website.

“Heating and Cooling with a Heat Pump.” Natural Resources Canada, Office of Energy Efficiency. Energuide. December 2004.

“Selecting Your Energy Source.” Natural Resources Canada, Office of Energy Efficiency Website.