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Is Geothermal Heating and Cooling Right for You?

While geothermal heating and cooling is a proven technology used in millions of residences worldwide, there are several questions a homeowner should consider before investing in a system.   Articles on several reputable web sites point to some of the challenges facing the industry and the need for the homeowner to go beyond what is normally done for conventional HVAC systems.   However, because the potential benefits are so significant, and the tools exists for homeowners to protect their investment, there has not been a better time to consider the switch to geothermal heating and cooling.

1. Find an experienced installer.

The International Ground Source Heat Pump Association (IGSHPA) has accreditation programs for both Installers and Drillers.   Look for an installer who is accredited, has experience in your area, and is willing to stand behind their installation.    International Ground Source Heat Pump Association (IGSHPA) has accreditation programs for both Installers and Drillers.   Be sure your installer and driller have gone through the proper training and check references.

2. Know your building load.

If you are in a northern climate, you will likely be heating dominated and want to design to meet your maximum heating needs.   For southern locations, you will want to focus on your cooling load.   The International Ground Source Heat Pump Association recommends that because the geothermal system is using your ground as the primary heating source (or sink), it is important that the system is properly sized.

Have your HVAC contractor conduct a “Manual J” analysis to determine your building load and consult with a building energy analyst to explore strategies for reducing your load.   Reducing your load by one ton of capacity can save thousands of dollars up front and provide additional savings in the future.   You can read more about the Manual J analysis in this article on the Residential Energy Services Network (RESNET) website.

When it comes to properly sizing a geothermal system, more is not necessarily better.  As noted in this article, oversizing the system results in both higher installation costs and a poorly performing system.

3. Be realistic about projected cost savings.

Geothermal heat pump systems offer the potential to significantly reduce energy heating and cooling costs and reduce greenhouse gas emissions.   GSHP system performance is often described by  a ‘coefficient of performance’ or COP that is the ratio of thermal energy produced to electrical energy consumed.    While the COPs of the heat pump equipment are certified in the lab according to industry standards, actual performance may vary and depends on details specific to the installation (e.g. power required to circulate the fluid through the ground loop, actual entering water temperatures over the course of a season, and the efficiency of the HVAC distribution system).

As shown in the figure to the right, once the installed COP exceeds approximately 3.5, most of the savings have been achieved and the costs savings associated with increasing the COP from 4 to 5 can be on the order of a few dollars per million BTUs (MMBTU).

Ask your installer what you can expect in terms of actual COP and what measures they take to ensure a high performing system.

4. Protect your investment.

A GSHP system consists of four interrelated elements, all of which must be designed to work together.   The building load is in response to the outdoor weather conditions and depends on the types of building materials used, the building load is met through an HVAC distribution system (usually forced hot air or radiant hydronic).   The distribution system is tied to a geothermal heat pump whose performance depends on both the ground loop temperature and the efficiency of the HVAC distribution system.   The ground loop extracts heat from the ground and its performance is based on the ground characteristics and the rate of heat being extracted.     When each component is properly sized and operates as designed, a GSHP systems offers unsurpassed performance.    However, if one component is not designed properly or is experiencing mechanical problems, it can affect the performance of the entire system.

Ground Energy Support offers a variety of monitoring options that can enable the homeowner to assess each component of a GSHP system  and identify issues that may be adversely affecting overall system performance.    Most often, these issues are minor and be easily addressed through routine system adjustments.    However, if allow to persist undetected, they can inhibit the system from operating at its full potential and could lead to unnecessary wear and tear of the equipment.

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