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Saving Energy From The Ground Up

My house needs a new heating and cooling system. I have thought about installing a geothermal heat pump for its efficiency and the tax credit. How efficient is one and how does it work?—Brandon D.

Geothermal heat pumps are extremely energy efficient and generally yield the lowest utility bills of any residential heating and cooling systems. With the high cost of energy and the available energy tax credit, installing a geothermal heat pump could make economic sense for some families.

A geothermal heat pump operates similarly to a standard heat pump except it exchanges heat with the ground instead of the outdoor air, essentially using solar energy, which is stored as heat in the ground.

The outdoor air temperature can vary 40 degrees or more from day to night and more than 100 degrees from the coldest winter night to the hottest summer day. In contrast, the temperature several feet below ground varies little.

To capture the heat energy from the ground in the winter or exhaust the heat during the summer, a long pipe is usually buried in the ground. Heat is transferred by an antifreeze/water solution running through the pipe. All new models use earth-friendly R410A refrigerant instead of Freon.

Efficient in all seasons
Since no outdoor condenser coils and fans are needed, the entire heat pump and all mechanical components are located in an indoor unit. It operates quietly and, with no outdoor fan or compressor, there is no noise to bother neighbors or your family at night.

During the winter, a geothermal heat pump can produce up to $5 worth of heat for each dollar on your electric bill. Unlike standard heat pumps, which lose efficiency and maximum heat output as the outdoor temperature drops, the efficiency and heat output from a geothermal heat pump remain relatively constant.

During the summer, a regular heat pump or central air conditioner loses efficiency and cooling output when it is hotter outdoors. Cooling efficiencies for geothermal units are as high as 30 EER (energy efficiency ratio). A standard heat pump or central air conditioner is typically less than half as efficient.

Another summertime advantage is free hot water when the geothermal heat pump is cooling your house. Waste heat can be diverted to your water heater with a device called a desuperheater.


The energy tax credit
The federal government provides a 30 percent tax credit covering the entire cost of installing a geothermal heat pump. To qualify, the unit’s efficiency must meet or exceed ENERGY STAR requirements. Units installed in 2008 were subject to a $2,000 cap on the credit. For any units installed in 2009 through 2016, you can take advantage of the full 30 percent tax credit.

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