How to Select a Geothermal Ground Source Heating System

Geothermal heating systems are an eco-friendly alternative to other heat sources.

A geothermal ground source heating system uses energy from deep underground to heat the home. These systems include hundreds of feet of pipes or tubing that collect heat energy and transfer it to above-ground blowers, which then distribute the heat throughout the house. Geothermal systems offer an eco-friendly alternative to furnaces or boilers, but require a substantial upfront investment. When comparing ground source heating options, consider size, technology, efficiency and special features to help you make your purchase.

Instructions

1. Calculate the size of a geothermal system needed for your home. A unit that's too big will waste energy, while one that's too small may not keep your home as comfortable as you'd like. According to Salt River Power Company, a general rule of thumb is to buy one ton of heating/cooling capacity for every 400 to 500 square feet of living space. While this rule of thumb can narrow your search, consult a contractor to provide a more precise sizing estimate.

2. Compare closed versus open-loop systems. A closed-loop system is refrigerant-based, and according to "Home Energy Magazine Online," often comes with a 50-year warranty. These units tend to cost more and operate less efficiently than open-loop units.

   Open-loop systems use groundwater instead of refrigerant. You must have sufficient, accessible groundwater in your area to choose this option. Open-loop systems often come with a 20-year warranty, but are less expensive and more efficient than closed-loop units.

3. Look for the efficiency rating on each system. The cooling efficiency of geothermal units is measured using an energy efficiency ratio (EER), while the heating efficiency is rated using coefficient of performance (COP). Higher COP or EER is associated with increased efficiency. The US Department of Energy recommends a minimum COP of 3.3 or 3.6 for closed and open systems, respectively, and a minimum EER of 14.1 and 16.2, for closed and open systems, respectively.

4. Inquire about the type of refrigerant used in each system. According to the Heatspring Learning Institute, the most common type of refrigerant is known as R-22. The EPA has declared R-22 an ozone-depleting material, and has required that it be phased out completely by 2020. If you choose a unit that uses R-22, you will likely have difficulty refilling or recharging your system once this product is phased out. Instead, look for systems that use alternative materials, such as R-401A.

5. Determine whether you want a geothermal unit that heats and cools the home only, or one that can also heat water. Systems with a "desupercharger" option contain a heat exchange coil and tank that can provide hot water for your plumbing fixtures.

6. Ask contractors for a break down of their pricing so you can perform an "apples-to-apples" comparison. Determine whether items such as installation, equipment, drilling, system design, warranty, service and maintenance are included or excluded.

References

• Heatspring Learning Institute: An Information Survival Kit for the Prospective Geothermal Heat Pump Owner
• Home Energy Magazine Online: Do You Dig Ground Source Heat Pumps?
• Salt River Power: Air Conditioning
• US Department of Energy: How to Buy an Energy-Efficient Ground-Source Heat Pump