Commentary: Pursuing geothermal heating pays off

Thirteen years ago, Gary Conway built his home with geothermal heating and cooling. He shares his journey with

When I built my home in 1998, my goal was to build a home that would be easy on the bank account and as easy as possible to maintain. Having owned (and maintained) homes previously, I recognized the value of a low- maintenance home as well as one that has low-operational costs.

Having an engineering background, I knew one unavoidable cost was the environmental system. It's not rocket surgery, but I realized that central to the idea of minimizing HVAC costs is insulation, in addition to the HVAC system itself. So I set about educating myself on the current technologies for both insulation and HVAC systems.

I had heard some interesting things about geothermal and conceptually, I thought I understood its principles. I learned that I didn't, and further learned there are many misconceptions about geothermal that are perpetuated by the uneducated. One of the more popular topics has always been whether geothermal derives its "heat" from the earth or the sun. I find this whole topic of discussion comical because these endless debates focus on this scientific fact and endless quotes of "irrefutable" sources, yet, they all miss the mark.

Geothermal HVAC systems are both heat sources and heat sinks. What this means is that during the winter, if the outside temperature is say, 30 degrees F and we are using our constant temperature water in the geothermal system of 55 degrees, we are adding 25 degrees of heat (heat source). In summer, and the geothermal system is in A/C mode, we are cooling 200-degree hot gases with 55-degree water, and this water returns that heat to the earth (heat sink).

On the surface geothermal seemed like an idea worth pursuing. I got quotes for traditional HVAC from several local distributors, each of whom sold well-known products in the industry. I also asked each of them to give me a quote on their geothermal systems. It was a surprise when they all said they could supply a geothermal system, but that I really didn't want it.

It was soon apparent that contractors’ real reason for dismissing geothermal was their lack of knowledge on the subject. It was then I realized I was really on my own in this quest.

geothermal heating unitAfter searching every corner of the Internet, I found that virtually all of the big-name HVAC manufacturers also offered a geothermal system, but no one really seemed interested in installing one. They all wanted to push conventional systems; in fact, they pushed three distinct systems for my home. Interestingly enough, all of the distributors quoted three systems for my home, yet ultimately, I installed a single geothermal system with four zones.

I quickly decided that a company whose primary focus was geothermal would best serve my interests.

There are several things that attracted me to geothermal in the beginning:

A constant temperature source

With conventional A/C, you have an outdoor unit that consists of a condensing coil and a fan. The idea is to cool the refrigerant gas back into a liquid. It's easy to see that if you are trying to cool something by blowing air across it, the cooler the air, the more efficient the job.

In conventional A/C, you have a fan in the outdoor unit blowing ambient summer air temperature air across a coil. Depending on your locale, this air temperature can be 100 degrees or more. Contrast that with the geothermal geothermal heating unitconstant temperature water at 55 degrees and using that to cool the refrigerant gas.

No outdoor unit

Conventional A/C systems have an outside condensing unit that is simply NOISY! Ever sit outside on a summer’s night trying to carry on a conversation over a glass of wine when the outside unit decides to kick on? You end up competing with the A/C unit. The idea of NO outside unit was extremely appealing to me.

Efficiency in heating and cooling

The efficiency comes from a number of sources in geothermal systems,not the least important of which was mentioned in No. 1 above. Other efficiencies include: no combustion, therefore no inherent drying of the air and no particulate by-products waiting for you to breathe them in. That my friend, is CLEAN heat!

With a geothermal system, you can redirect the heat removed from the refrigerant gas during the A/C cycles and pump that heat into your hot water heater.

No combustion in the home

There is no combustion in geothermal as there is in gas heating. Aside from the fact that you don't have a FIRE burning in your home during heating season, you likewise do not have the fumes and particulate by-products of combustion floating through the rooms.

Energy efficiency, i.e. an electric bill that doesn't take on a life of its own

If we examine electrical costs and compare a geothermal unit to conventional electric heating, geothermal wins hands down, because conventional electrical heating runs a LOT of electricity through heating coils and converts electrical energy directly into heat, which is very expensive. Comparing geothermal to a gas system, we see that the gas system has to have a constant supply of combustible gas, either natural or propane, both of which are relatively expensive. Geothermal wins again.

During my research, it became abundantly clear that the ground loop is an essential ingredient of the system and the efficiency of this loop determines the overall efficiency of the entire system. Because of this I chose to use vertical lines, that is, four 150 foot holes with a loop chained between  the four holes.

The system pumps what amounts to antifreeze through this loop. If you think about a cave and the relatively constant temperature inside that cave, you can easily see that the fluid in the loop stays at a relatively constant 55 degrees year round. I have found that this concept is both critical and essential to a geothermal system's efficiency.

Being a geekazoid, I built a monitoring system that consisted of a computer, software and some custom hardware. The objective was to monitor the power (kwH) required by the geothermal system and plot that against what stage of heat or A/C that the house was calling for as well as internal and external temperatures. Since the geothermal system is computer controlled and extremely configurable, this allowed me to tweak the system for seasonal changes weighing electricity costs versus household comfort levels. I realized most folks aren't about to go to this extreme; however, it does serve to show that if you really want to save that last few dollars on electricity, you can.

One of the greatest beauties of the geothermal system is that the temperature and humidity in the home remain substantially constant. This has numerous benefits. You won't find yourself stepping onto a cold floor in the morning and all of the accoutrements in the home aren't constantly expanding and contracting with varying temperature and humidity, which certainly goes a long way toward increasing their life expectancy.

In the 13 years since the home was built, the savings has certainly paid for the $3,000 more that the geothermal cost initially, but more than that, the electrical savings has paid for the entire geothermal system itself. If you have plans of staying in your home for any length of time, then you simply can't afford not to give a hard look at geothermal. You'll be grateful to yourself later, I can promise you.

For more information, see our Energy-efficient Heating and Cooling Research Center.

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User Comments – Give us your opinion!
  • Anthony Downing
    As a designer / manufacturer of renewable energy systems, including geothermal, it's gratifying to see another example of a homeowner who recognizes the potential of geothermal energy. A couple of thoughts to consider:

    REHAU (who I represent) produces PEXa pipe, which is a terrific choice for geothermal applications, given the robust performance of the pipe, compared to the more familiar HDPE.

    Also, we produce a ground air heat exchanger (GAHE) called ECOAIR, that uses the same principle, i.e. ground-stored solar heat in winter, relative cool temps in summer, to precondition ventilation air through underground pipes that feed into your HVAC, or HRV system. These so-called "earth tubes" can reduce the energy demand of your home's HVAC system, which as we know, can be a considerable portion of your energy consumption.

    Like ground loops, earth tubes have been around for centuries, and are a widespread technology for capturing renewable energy in Europe.
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