Many homeowners are choosing to upgrade their conventinal HVAC systems to geothermal heat pumps. Those who are building new homes are also learning the advantages of geothermal heat pumps vs. conventional heating and cooling systems in new construction. Are they worth the extra expense? Many homeowner’s around the country, including myself, have already jumped on the ground source heat pump bandwagon. While solar and wind seem to get all of the attention, we are largely ignoring one of the most accessible and affordable renewable energy sources in the world, geothermal energy in the soil only a few feet under our feet. Why is this so? For one reason, most large home builders would rather keep on building junky, inefficent boxes, which they turn around and sell us at a large profit, rather than do a few things that require a bit more effort but which can pay the home buyer back hundreds of dollars a month over the life of the home (such as spray foam insulation and geothermal heat pumps). Let’s take a look at the advantages of ground source heat pumps vs. conventional air conditioners and heating systems. First off, just to be on the same page, know that geothermal heat pumps, (GHP) are also called GSX, GSHP, ground source heat pumps, as well as other names. It seems that the former name is becoming the most commonly used in the industry. Below is an illustration of a ground source heat pump intallation.
How Does A Geothermal Heat Pump Work?
When we think of the word “geothermal” many people envision hot steam that is tapped deep underground and used on the surface to turn turbines and make electricity. Geothermal energy is simply potential thermal energy of any kind that is trapped in the ground, and which can be used on the surface for a vareity of purposes. The way that a ground source heat pump works is very much similar to a conventional HVAC. Both will likely use R-22 refrigerant, a compressor and evaporator unit. Both systems are designed to do basically the same thing, which is to heat or cool the air in your home. The difference is that the conventional HVAC or heat pump is using outside air as the medium from which heat or cold is exchanged. When it is fifteen degrees Fahrenheit on a cold North Dakota morning, a conventional heat pump will be working especially hard to pull heat out of the frigid air and convert it to 80 degree air inside the house. A geothermal heat pump on the other hand would have the advantage of using the temperature of the ground a few feet under the surface, which might be fifty degrees or more, to make that 80 degree air. Since you’ve spotted the system several degrees it won’t have to use as much energy. SEER ratings, a measure of air conditioner energy efficiency, are very hard to apply to heat pumps. This is because these numbers tend to be based on seasonal air temperature changes. Since the temperature of the ground remains basically the same year round this makes it hard to use SEER to rate geothermal heat pumps. Also, since many systems can make “free” hot water for a home as well, this adds even more energy efficiency to the unit. Most installers agree that ground source heat pumps are anywhere from thirty percent to fifty percent more energy efficient than the most efficient air exchange HVAC and heat pump units. For a detailed analysis of heat pumps you can take a look at this research paper from the Oregon Institute Of Technology
Geothermal Heat Pumps Vs. Conventional HVAC
Studies have shown that even if you have to take out a loan to completely replace your existing system with a geothermal heat pump, the advantages of the new system will mean you will still have extra money in your pocket each month, in addition to adding value to your home. The payback of geothermal heat pump cost is around ten years. Popular Mechanics reported that the average cost of a ground source heat pump, after federal rebates, is around $19,000. The annual operating cost of the geothermal heat pump would be about $1,800 less than a conventional system, leaving $132 to pay the loan and $24 in your pocket. When done as a part of new construction you can gain a savings of about $156 a month in electricity costs for just a few bucks more on your montly mortgage cost. Add in the fact that many ground source heat pumps also make most of a home’s hot water at barely any extra cost, you quickly realize that you can’t lose by installing one of these sytems in your new home.
The only disadvantage of geothermal heat pumps is that you will need a big enough lot for a series of vertical wells to be drilled or for coiled pipe to be placed in a trench. If your home is next to a pond, the coils can be placed in the water. Not all properties are suited for ground source heat pumps, but many are. Having installed a geothermal heat pump system in my own home is a decision that I don’t regret one bit.
By “Sunshine”. Author’s note. Our geothermal heat pump system is now five years old and has been working flawlessly during that time.