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It’s important to understand that there is no simple response to this question. That’s because there are so many potential variables with every home and its structural and heating, ventilation and air conditioning (HVAC) details. There are two main types of heat pumps: air-source and ground-source. People often get them confused. To complicate things even more, there are many variations on these two main categories. In any case, air-source heat pumps use latent heat in the air to heat or cool your home. However, air-source heat pumps are generally not good choices in cold northern climates where the winter temperature regularly falls below 32 degrees Fahrenheit. In cold winter conditions, ground-source heat pumps really shine.

Ground-source heat pumps, often referred to as geothermal heat pumps, rely on latent heat in the ground (or ground water) to heat or cool your home. It’s important to understand that some homes, due to structural or other site constraints, may not be appropriate locations for a geothermal system at all. In other cases, it might be a hard call: theoretically possible, but extremely difficult or costly from an installation standpoint. But in many instances, particularly with new construction, it’s a straightforward cost comparison issue.

Over the life of your heating appliance, the most important cost is for the fuel to operate it. And in general, it is reasonable to expect that the cost of gas and oil will continue to climb irregularly in the years ahead, making any heating appliance that depends on them a risky long-term choice. A heat pump, on the other hand, relies mainly on electricity, and while we can expect the cost of electricity to rise too, there is potential for more and more electricity to be generated from renewable sources in the future. What’s more, the cost of electricity will not be rising as quickly as the price for fossil fuels, offering an additional advantage for heat pumps.

The operating cost of a typical fossil fuel-based system is 95 percent the cost of the fuel and about 5 percent the electricity to run the system, according to Harold Rist, a respected and experienced ground-source heat pump installer in Queensbury, N.Y. The operating cost of a geothermal system, on the other hand, is about 70 percent to 75 percent nonpolluting “free earth energy” and about 25 percent to 30 percent electrical energy. Better still, an Energy Star-rated heat pump uses about 30 percent less electricity than a standard heat pump. It should be clear even from these rough estimates that over the long haul, a geothermal heat pump can offer the best heating and cooling option for many homeowners. In fact, the Environmental Protection Agency says that geothermal systems are the most energy efficient, environmentally clean option to heat and cool a home.

The main hurdle for most homeowners is the high initial investment in a typical geothermal system. This can run from about $8,000 to $20,000, depending on a wide range of variables. Air-source systems are generally less expensive, and generally run between $2,000 and $5,000. And if you live in an older home with a small (under 200-amp) electrical service entrance, you will need to upgrade to a 200-amp (or larger) service entrance. In any case, crunch the numbers, and see if a heat pump makes sense for you and your particular house. If you decide to install a heat pump in your home, you can relax in the knowledge that while fossil fuel prices will fluctuate wildly in the future, your primary fuel source will always be available — and free.

Check out Magic Heat Pumps, too.

— Greg Pahl, author of Natural Home Heating: The Complete Guide to Renewable Energy Options (Chelsea Green, 2003)

7 Comments

  • hime8 12/14/2008 9:56:05 AM

    going on 18 years we have had a ground water heat pump.we are now all electrice the heat pump all so makes hot water.this works well for us and is very coast efective.we run at 70 in winter 78 to 80 in summer. our bill is around 1,000 per year.put in a fan motor and a pump so far.i am thinking of a wind ginorator now.would be great! bob

  • william 12/12/2008 11:52:21 AM

    As I understand it ground source heat pumps transfer the heat to water. This low temperature water(120 F)is circulated through radiant floor heating system. You cannot circulate it through a baseboard hot water system which is designed to use hotter water. So the cost of installing a radiant floor heat system is a major issue.

  • going green in caseyville il 11/17/2008 4:47:12 PM

    EVERYONE,Exciting news,

    I just read about a new cold temperature air source heat pump that was featured in This Old House magazine recently.It is called the Acadia and manufactured in Maine.It is supposed to be as efficient as a geothermal ground source heat pump, but costs substantially less to install, and works well down to MINUS 30 compared to the +30 for regular heat pumps. They have been available only since 2005, so that may be why few people have heard of them.It is definitely on my wish list, as propane is up 20% this year.Insulating or radiant barrier paint additives also lessen the need for heating and cooling, and can be used indoors or out.Anything radiant barrier is useful in my opinion, but the paint additive lets us set our thermostat at 60-62 and feel 5-8 degrees warmer in winter.

  • Stacy 10/27/2008 2:27:04 PM

    We installed an air source heat pump about 4 summers ago. And love it! We live on the Canadian border in Northern Minnesota. So we also have an incorporated propane heating unit that takes over once the temperature drops below freezing.

    While our new heat pump was a huge investment for our family budget, I'd say it was well worth it.(We also had in upgrade to a 200-amp service at the same time.)Our monthly electric bill actually went down. We elimated use of ceiling fans in main rooms in the summer and the burdens of the wood stove completely.

    I would highly recommend either heat pump style to any one that might be interested in them. The geothermal is the best route in my opinion (if you can afford it). The air source is a cheaper investment and still saves on the pocketbook and the environment.

  • Derek 10/21/2008 3:45:57 PM

    In my limited understanding, first generation ground source heat pump did just that. No compressor, but made use of the constant temperature of the earth. They were able to cool your house to a point in the summer and heat to a point in the winter, but you needed another system to bridge the gap. I have heard of others asking about such a system, but have heard of no one that would install that configuration.

  • Jim 10/18/2008 1:20:32 AM

    The references to latent heat in the article are incorrect. Latent heat is involved with a change in state of a substance. When water changes from a liquid to a vapor, latent heat is absorbed; when water vapor changes to a liquid, latent heat is released.

    From Wikipedia, the free encyclopedia

    "In thermochemistry, latent heat is the amount of energy in the form of heat released or absorbed by a substance during a change of phase state(i.e. solid, liquid, or gas), – also called a phase transition."

    If the word "latent" in replaced with "sensible" the article will be correct.

    One other note, the last sentence should read "primary heat source" vs "primary fuel source".

  • Brad 10/1/2008 5:40:29 PM

    I wonder about a non-compressed ground-source pump. Is there a way to reduce cost and energy use by sacrificing the extra heat you could get from a compressor and content yourself with just the latent ground heat? It wouldn't be enough to heat the house in our cold Northern Michigan winters, but it would be enough to keep the pipes from freezing and could be the perfect backup to a masonry stove. And of course it would work wonders in the summer. Anyone heard of this, or am I missing something?

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