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Green Building Blog

PRO/CON: Are Heat Pumps Green?

A heat pump draws heat from the air, earth, well water, or pond water and uses that energy to heat or cool a house

All heat pumps work on the same principle, moving heat from one location to another with the help of a closed refrigerant loop, a compressor, and a heat exchanger. In winter, heat is extracted from air, water, or the earth; this heat is used to heat the house. In summer, the process can be reversed so the heat pump pulls heat from the inside and dumps it outside. A heat pump can be used with either a forced-air or hydronic distribution system.

They seem like the perfect Green technology and that’s why they’re so popular. According to the EPA, they’re extremely efficient. Problem is, it’s more complicated than it seems. They use energy from an inefficient grid that often burns coal to make power.

So are they green?

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John D. Geyer, a geothermal designer, trainer, and consultant in Vancouver, Washington says that their high efficiency means low operating costs. Read more

Henry Gifford, an energy consultant in New York City, says that high-efficiency boilers and furnaces are much more efficient. Read more


FURTHER RESOURCES

Green Building Encyclopedia:

Heating Options

Heat Pumps

Blogs:

Ground-Source Heat Pumps

Air-Source Heat Pumps

Heating a Tight, Well-Insulated House


10 Comments

  1. Aaron Lubeck` | | #1

    Heat pumps are the cheapest
    Heat pumps are the cheapest to run traditional system availible in the South, but natural gas is probably greener.

    Amory Lovins sums it up: "Heating with electricity is like cutting butter with a chainsaw."

  2. Stephen Colley | | #2

    Makes More Sense in Hot Humid Climates
    In our climate (South Central Texas), winter is brief, and summer is seemingly forever. Where air conditioning and de-humidifying rule, heat pumps (and particularly, geothermal heat pumps) begin to make sense. There's no natural gas fired air conditioning, so I'm assuming that the energy expended by a geothermal heat pump saves much more electricity (from our primary source - coal) in the summer months (air conditioning season is mid-May through mid-October) than is generated during the winter. I wish I knew the numbers on that one. Better yet, using the geothermal heat pump in the summer and not using it in the winter, in lieu of an EPA rated stove or efficient gas heat warrants looking into.

  3. Carl Mezoff | | #3

    Ground Source Heat Pumps
    Henry Gifford is right on target in saying that ground source systems are often overblown in their claims of low energy consumption. Having designed several commercial ground source heat pump systems in the 80s, we found that when pump energy is included, the system's overall energy performance is usually mediocre, and often less than that of a simple air source heat pump.

    When you include the expense of wells or ground loops, intricate control systems, a room full of HVAC equipment and maintenance costs (by your local PhD engineer-the only guy who can understand the system), it makes much more sense to put those dollars into a better envelope (passive design, triple glazing, super insulation) so that the requirement for heating and cooling can be met with a tiny and simple auxiliary.

  4. Mike Caldwell | | #4

    heat pumps
    There's too many variables for any one statement to cover earth-coupled heat pumps "green" value.

    I'm afraid the article did little to further the understanding of the subject, especially for the average person trying to decide what system is best.

    In my situation a water-coupled heat pump will be very "green" since as it's water source it will use a spring-fed stream whose temperature varies little. My area also has moderate winters so most of the work will be cooling which a heat pump can do very efficently. Natural Gas is not an option here so I'll do my best to use as little electricity as possible and that means an earth-coupled heat pump.

  5. Alex | | #5

    heat pumps
    I live in the Cincinnati, Ohio area, and have an air source heat pump. My home is very well insulated. In the winter, we mainly heat with a wood stove, so the pump is mainly for summer cooling. When I replaced my heat pump this winter, I looked into ground source. Even if my electric bills were $0, I would not live long enough for the pump to pay for itself. I think that the money is better spent on more insulation and better air sealing.

  6. Anonymous | | #6

    How "Green" is Natural Gas
    I find these articles humerous and full of ones particular agenda for writing them. How "Green" is natural gas when compared from well head to end use. The last time I checked natural gas doesn't appear magically at someone's home to burn, and people certainly don't have their own gas well. The gas is either drilled and extracted in the gulf of mexico, southern part of the country, or western US, either eay it takes a lot of energy to get the gas, then to pump it and deliver it all across the country just like electricity. All the bogus reports and articles that are out there never compare apples to apples. They only compare the geothermal heat pump with a coal fired plant buckled to it for emmissions, and then to a unitary furnace with no gas distribution or production included. How is that a fair comparision. I would ask that all these so called experts do the proper fact finding and come up with a true apples to apples comparison. Oh yeah, the DOE and EPA has done that and found that a geothermal heat pump is still the most cost effective way to heat and cool a home along with the lowest GHG emmissions. Now what if that electricity was being generated by wind or biomass, which is becoming very popular in many areas around the country. Also, if these experts new anything about electric generation, they would understand that a geothermal heat pump is the best heating and A/C system for evening the load factor of the power plant and making the overall generation system more efficient by not having the spikes in the summer and more even load during the winter. And when it comes to payback there are thousands of systems being installed with less than a 10 year payback. Show me any other renewable technology that can show that kind of payback. It isn't going to happen, and if someone doesn't think they are going to have a payback, then yes geothermal isn't for you. It doesn't work for all in every case, but 90% of the time, it is the best way to go. And for the wood burning demographics, well I guess if you figure you time isn't worth anything, your gas to fire the splitter, chainsaw, and truck to haul the wood, or if you are buying wood you would figure all those costs in, I know from experience that it does pay for itself. To many people have blinders on and don't look at the entire picture when comparing these systems, but they have heard from a buddy, or maybe the gas company, or some report that was done by a so called engineer who again didn't do the proper fact finding. All the data is out there, so go find out for yourselves rather than taking someone's word for it on a blog.

  7. GBA Editor
    Martin Holladay | | #7

    GSHPs are not a "renewable energy technology"
    Anonymous,
    You are mistaken: GSHPs are not a "renewable energy technology." They are heat pumps, just like the heat pumps found in air conditioners and refrigerators. They require electricity to operate.

    As for whether "a geothermal heat pump is still the most cost effective way to heat and cool a home" -- ductless minisplit air-source heat pumps from Japan and Korea are far cheaper.

  8. Tony | | #8

    Heat Pumps
    It got down into the 20's last night and the heat pump would not heat the house. What is wrong and how do I make it work? We live outside Atlanta.
    Thanks

  9. GBA Editor
    Martin Holladay | | #9

    Response to Tony
    Tony,
    If your heat pump isn't working, you'll have to call a repair person. We can't diagnose or repair your heat pump over the Internet.

  10. Andy Parkinson | | #10

    Refrigerants
    What about potential impact of the refrigerants used in heat pumps. Should we also be factoring in the GWP of HFC (or other?) used in heat pumps. Or is this not a concern if units are disposed of correctly.

    We've seen that the blowing agents used in some foam insulation can have a significant GWP, is this a concern with heat pumps or not?

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