To answer your question upfront: I am a raving fan of geothermal HVAC, or rather, ground-coupled heat pump HVAC.
There are additional details to consider if this HVAC system is right for you.
Energy Audit
Have you had a recent home energy audit? A home energy auditor will assess the building envelope of your home to discern if there are any major components that need to be addressed before you make the investment in geothermal.
If your home is leaking air (and heating and cooling) it will require a larger HVAC system. If your
- windows need to be replaced, your
- attic insulation is not adequate or your
- basement has no insulation at all . . . geothermal might not be the area to invest your energy savings dollars right now.
Geothermal installation
When you install a geothermal system it will require you to drill wells into the ground (vertical) or a web of pipes across your yard below the frost line (horizontal). The size of these wells are calculated based on the heating and cooling needs of the home.
The better your home is insulated and sealed, the smaller the wells or webs.
- Since a large portion of the cost of geothermal is spent on wells and webs, you can mitigate the ultimate cost of geothermal by first tightening up your building envelope and converting to geothermal later (if your current heating and cooling system is still working).
- Do you have space on your property for the wells and webs? A typical geothermal system here in the Northeast will require 150 feet of vertical wells per tonnage of heating and cooling needed. These wells need to be spaced 10 feet apart. For a smaller house that requires a three-ton system you will more than likely need two vertical wells to be drilled in an area of your yard that is free from easements, setbacks or other utility or sanitary systems.
- Will you be staying in your home long enough to see a return on your investment? Large systems upgrades such as this normally require some time before you see a return on the money you've spent on the upgrade. If you've reviewed the conditions above, you can plug your current home specifications into this tool to estimate your savings per year and determine how long it will take before you begin making money on the investment.
- The possibility does exist that if you plan on selling your home a homebuyer will appreciate the upgrades you've made. Keep the documentation you receive from your home energy audit and the printout from HES to show future buyers that your home is energy efficient.
Lastly, don't let this question interfere with your willingness to self-regulate your carbon footprint. Not all green decisions have to be purely economic. The HES tool will also tell you your carbon reduction as a result of making changes to your home and HVAC system. They shouldn't be ignored.
Tax credit
Don't forget the tax credit! If all the criteria above are met and you will be staying in your home long enough to reap the savings from your investment, you can tack on the savings for the tax credit for installing a geothermal system in your home.
For more information, here is a link to the Energy Star webpage for this particular credit and another link to their FAQ on geothermal systems.
Good luck with your project!
For more information:
Read Mick Dalrymple's Q&A "Are geothermal heating/cooling systems better in reducing energy costs than solar power?"