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The ‘other’ geothermal grew 33% in 2006

By Joe Romm  

"The ‘other’ geothermal grew 33% in 2006"


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Baseload geothermal power gets all the attention because it has such enormous potential for delivering low-carbon 24/7 power (see “Hot rocks are a rockin’ hot climate solution“).

geothermal-pump.jpgBut geothermal heat pumps (GHPs) are every bit as deserving of attention because they are the most energy efficient form of heating and cooling a building over much of this country [click on figure to enlarge]. And if you power GHPs with a renewable source of electricity, they are probably the best way to eliminate the need for natural gas heating in the winter while at the same time slashing peak demand in the summer.

The U.S. Energy Information Administration released their “Survey of Geothermal Heat Pump Shipments, 2006” last month. It found “that manufacturers shipped 63,682 geothermal heat pumps (GHP) in 2006, a 33 percent increase over the 2005 total of 47,830.”

Here is some background on the technology.

Geothermal heat pumps (also, ground-source heat pumps or GeoExchange systems) provide both heating and cooling. They typically run piping a couple hundred feet below the earth’s surface (or occasionally connect to a nearby body of water). Here the temperature stays relatively constant throughout the year.

Since the ground is warmer than the outside air in the winter, GHPs expend less energy than conventional systems to heat up a building. Similarly, since the ground is colder than the outside air during the summer, GHPs expend less energy than conventional systems to cool down the building. Thus, GHPs maintain high-efficiency all the time in virtually any climate. Indeed, when it is very hot outside or very cold outside, that is exactly when there is the largest temperature difference between the outside and underground, and so geothermal heat pumps are ideal and severe climates or climate characterized by high daily temperature swings.

The idea of geothermal heating is quite old. Hot spring water was used to heat bathhouses back in ancient Rome. The first patent on the technology dates back to 1912 Switzerland, and systems such as the one at United illuminating in New Haven, Connecticut have been operating since the 1930s. But only in the last two decades has technology improved to a stage where the market for GHPs is rapidly expanding.

Compared to conventional systems, GHPs typically have higher initial cost but lower maintenance and energy costs. They require less floor space than conventional heating and cooling systems because the exterior system is underground. They are very quiet and long-lasting. Also, they can provide simultaneous heating and cooling. For example, in the summer time that they can provide both air-conditioning and hot water.

The EPA compared a variety of different heat pumps and found that GHPs can reduce energy consumption and, correspondingly, emissions of greenhouse gases and other pollutants by 23% to 44% compared to more standard heating and cooling equipment. Geothermal heat pumps have superior environmental performance in virtually all locations except where the local electricity was very coal-intensive in which case gas-fired heat pumps were superior. Of course, GHPs are best suited for new construction or major retrofits were digging up the ground is viable.

Certainly if you are planning to build a house, GHPs should be something you seriously consider.

If you want more technical details Wikipedia has a good entry, and here is a good FAQ .

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29 Responses to The ‘other’ geothermal grew 33% in 2006

  1. Ronald says:

    spelling Fourth paragraph from the end. ‘both air-conditioning and high water.’ shouldn’t that be ‘both air-conditioning and hot water.’

  2. Pierre Gosselin says:

    Now you’ve posted something positive, constructive and interesting, not that I myself am interested in reducing my CO2 footprint. Moreover I’m intersted in saving money. GWB’s Texas ranch has a similar system.
    If you wish, I’d be more than happy to send you details.
    I won’t go into Al Gore’s TN mansion :)

  3. Rick says:

    Joe, does it work in places, like here in Houston, where ground water tables are high?

  4. Lou Grinzo says:

    While I agree with everything Joe says here, let me stress one point: The potential difficulty of adding a GHP on a new house. I’ve been horrified by all the stories I’ve heard from reliable sources about the difficulty in getting builders to make even tiny changes related to energy consumption. One friend of mine who built a house about 2 years ago in the NE US couldn’t even get the builder to add an extra layer of fiberglass insulation to the attic at added cost. The same builder gave my friend exactly one heating option: Propane. The builder did offer a wide selection of media rooms and other goodies, though.

    I suspect that adding a GHP to a new house project will entail more than just paying a little extra upfront and checking a box on paperwork; in many areas of the US it could require some legwork to find a builder both willing and able to do the work. From everything I’ve seen of GHP systems both in writing and in person, I think it’s well worth the hassle.

  5. Doug says:

    Rick — given that it can work w/ lakes as the heat source, I’d imagine a high water table would be fine.

    By the way, these systems don’t necessarily have to drill hundreds of feet deep; that’s just an option if you want to minimize the disturbance to existing landscaping, or just don’t have room (e.g. in a city). If sufficient adjacent land is available, the cheaper option is to dig a series of narrow trenches about 6ft deep, and coil the tubing in there.

    I have yet to find out how much land area is generally needed for that arrangement. But the typical system size for a residence seems to be “3 tons” (I don’t know what that measurement refers to), costing $7500 (using a “$2500 per ton” rule of thumb).

    I found a lot of good info here:


    A heat pump, combined with electricity from solar/wind, seems pretty necessary to me, if you want to truly eliminate the carbon output of your house.

  6. Andy says:

    Pierre, it’s unlikely Gore would invite you into his mansion, anyway.

    I would like to say I won’t go into GWB’s complete disregard for the global environment, but I don’t have a choice. I live in it. How two men outfit their private residences is very different from what they are trying to do (or not do) for broader society as a whole. Look at what Gore is proposing versus what Bush has done. I vote for the guy with the high gas bill. Actually, a lot of people did vote for him. I really won’t go into THAT one.

  7. Brad F says:

    I have to echo what Lou said. I bought a house that was already under construction last year, and had the opportunity to make quite a few changes to what the builder would have done had he finished the house on spec. My builder was pretty easy to deal with, but most changes were going to cost more and take longer. Taking longer was not an option. My marriage depended on being in the house by a certain date. In the end, I didn’t get the ground source heat pump I’d always wanted – there just wasn’t time to find someone who could do it, and get it done correctly, and get the bank to loan me the extra 18-20 grand when I was near my limit. I was stuck with the windows that were already in the house, though I would have paid to upgrade to triple panes. I couldn’t reasonably insulate with spray polyurethane foam, the cost adder was just too high and hardly anyone does that work here. I did, however, get a drainwater heat recovery unit installed and we heat with an in-floor radiant system so either a heat pump or solar is a potential upgrade.

    Overall, the entire building industry seems ignorant of many measures needed to lower energy consumption. Their business model is based on the lowest price to install, not the lowest cost to own. And much of the lowest cost to install decisions are based on what supplier the builder has a high volume, low cost contract with.

  8. Ed D says:

    I think the name “ground source” is much better than “geothermal” for these heat-pump systems: it avoids confusion with heat from molten lava.

  9. Jean says:

    Do you have to use something like antifreeze to keep pipes from freezing in the winter??

  10. John says:

    This has been big business for a while in Sweden. There is one small problem, you still need power to heat your house. If you are planning to build a new house (or renovate one seriously) I would recommend looking at passive houses instead. Why not skip the habit completly? If we are serious about climate change, energy should become more expensive.

    Just one example;


  11. RhapsodyInGlue says:


    Rather than being a problem, I think high ground water table actually helps. The thermal transfer is greater and thus would likely require less drilling for comparable capacity.

  12. Lloyd Alter says:

    “The idea of geothermal heating is quite old. Hot spring water was used to heat bathhouses back in ancient Rome.” arrgh! Ground source heat pumps have NOTHING to do with geothermal heating like the romans used. It is using the ground as a more effective heat sink than the air. It is an air conditioner/heat pump that uses electricity to move heat when we should be designing houses so that they don’t need heat or cooling through proper insulation, shading, trees and location, like anywhere but phoenix.

    It is also appropriation of a name, geothermal, that has an important role to play, by an industry that had trouble selling GSHP, or ground source heat pump- it sounds greener. It is confusing the public and selling a more efficient band-aid to bad design.

    I wrote in TreeHugger:

    Geothermal systems use heat directly from natural sources like hot springs, geysers and volcanic hot spots like the installation on the right in Iceland.

    Ground source heat pumps are air conditioners that use groundwater or simply soil to cool the condenser instead of an outside coil and fan. It uses electricity to move heat energy from one place to the other. Run it backwards and it provides heat, more efficiently than using the electricity directly.

    They are not the same thing.

    [JR: The point is -- The idea of tapping the earth's heat for heating is an old one. I think everybody got the message, and I'm not sure anybody was confused. To anybody who thought that what the Romans did as much to do with a geothermal heat pump, my sincere apologies.]

  13. Maria says:

    Are there any life-cycle economic analyses on this? for instance, how long does it take energy savings to repay the extra capital cost? Do energy savings ever pay for higher initial costs? Thanks.

  14. David B. Benson says:

    Maria — CalTech, in a new building, paid an extra $4 per square foot for a top LEED rating. They state they expect savings of at least $67 per square foot over 20 years.

    The Architecture2030 site probbly has more info.

  15. Maria,
    That would be highly variable, depending on the climate and existing energy costs. In places with high heating or cooling loads payback will be much faster. Right now in moderate climates and current energy prices it is still a fairly long payback (maybe over a decade?). Geothermal heat pumps are also a lot cheaper if built in new construction and would pay back much quicker.

    The point above about passive construction is well taken: Passivhaeuser in Germany use 15% of the heating energy of regular buildings through superinsulation and the use of air-to-air heat exchangers. However on retrofits, a geothermal heat pump is usually more practical as it is less expensive than trying to make a non-passive house so tight that it meets the passive house criteria.

    Geothermal will become more practical as a retrofit as energy prices go up.

  16. Tom says:

    Has anyone calculated what the impact of taking all that heat (all the homes and buildings) from the earth. Remember mars does not have a molten core, thereby there is no magnetic field around the planet, causing it to be bombarded with the full spectrum of the suns output making it a dead planet. I know we are in despirate times but some sort of study should be done. We already have screwed up the atmosphere, lets not mess up the planet to.

  17. Damon says:

    For those of us who can not afford a $20,000 geothermal HP, I suggest a Air Source HP. For about $5000 installed, an air source HP will provide efficient heating down to 23 degrees F at which time it automatically switches to a preferably 95% efficient natural gas fueled furnace that costs $3000-4000 installed. This is a hybrid solution that works well in the very cold midwest, particularly Minnesota where I live. This is very green and econonomic as it’s half the cost of heating compared to gas per million BTU’s. An Air Source Heat Pump provides 9 months of heating and cooling in our very cold climate.

  18. David B. Benson says:

    Tom — It is simply too small to matter.

  19. Dave says:

    I replaced my propane heating system for a 5,000 square foot home in the St. Louis, MO area with a geothermal or ground-source heating system (whatever you preference) this past year. It cost me about $20K, but I saved $4,000 in the first year on propane. My electric bill increased only slightly, if at all. It is hard to compare years because of difference in weather conditions, plus I replaced all my light bulbs with GFCs and have been trying to generally conserve electricity. However, what ever my assumptions, this has been a great investment for me and investing in this system really out performed the stock market in this past year. This is a no-brainer if you are using propane.

  20. Anna Haynes says:

    Seconding Jean’s antifreeze Q above. What happens when the system springs a leak? especially if you have a well nearby?

  21. tom says:

    Dave – that is what they said about co2
    and the people that were talking about the peaking of fossle
    fuel production were discredited back in the early 60′s
    I heard something intersting recently
    There are three classifications of civilitions from SETI
    CLASS 1 -obtains their energy from the planet they are on (weather)
    2-obtains their energy from the solar system they live in
    3-obtains their energy from the galaxy they live in
    We are a class 0, obtaining our energy the same way the cave man did
    Burning the remains of dead plants and animals.
    The military is (right now)using high gain antennas to direct beams of
    energy at its foes.
    Why cant the same technology be used to extract the energy out out
    of some of the storms we experience in the US.
    Antennas can be erected in high lightning areas of the country to
    charge capacitor banks. these are just a few.I belive cold fusion is
    still on the table. But it is going to be tough to get people out of the
    cave we are in, and change the way we live.
    It would be ok to obtain thermal energy from naturally occuring cracks
    in the mantle of the earth, as in Iceland,but say a signifigant amount of
    people started to change the temperature dynamics of the earths mantle
    I am not sure if it could cause a new crack, plume, or break off a new
    tectonic plate. It just happens to be the fact that the St Louis area sits above an ancient fault n the earths crust-that is why they have had devestating earth quakes there,in the past.
    Isn’n it somewhat like the rush to buy those kits to convert used deep
    fried fat to diesel,well did any boudy think there is only so much of this
    grease around.One of the fastest growing crimes, in california, right now
    is the theaft of left over grease from the local KFC.Who would have
    thought about that one!
    The people are going to nave to demand a strong energy policy from
    government, industry,and even from our selves,before it is too late.
    What ever happened to pulse combustion boilers,for home heat.I had
    one years ago,and the gas company did not know I had gas heat,
    because of my usage.

  22. John says:

    As far a screwing up the planet… the impact is of geoexchange is tiny. A vertically installed system to a depth of 75 feet and is no where near the core of the planet and is taking energy from a footprint barely larger than the building. The earth absorbs 47% of the sun’s energy and continues to do so. By the way…. when you run the AC, you put some heat back in. Far less environmental impact than drilling for natural gas, oil, and mining coal, transporting it everywhere, and then burning it all to make CO2.

    Concerning price… if new construction, it on the mortgage. Get an Energy efficient mortgage and increase your buying power. For the extra $100 – $150 a month you SAVE significantly MORE on utilities, save on maintenance costs, have more comfort, less noise, your house is worth more, have no carbon monoxide issues, and don’t even need a chimney. If it’s a retrofit, finance over 10 or so years and you save the first month. Kind of a no-brainer.

  23. HeatPumpGuru says:

    Here is a link to a very complete site on all you need to know about Geothermal
    Geothermal Heat Pump at Home

  24. Bill says:

    Bio degradable antifreeze is used. Not for preventing freezing (the system is underground, so its at about 55 degrees year round), but to avoid corrosion to pumps and valves that can happen if you use straight water.

    In our house, they buried an extra loop, so if one springs a leak we have a spare.

  25. James says:

    We live in Houston, Texa and have two 20 year old systems, one is 4 tons and the other is 2-1/2 tons. We have a large yard and are interested in retrofitting with geothermal, but can’t find very many HVAC Contractors that advertise geothermal. Is geothermal a good solution for heating and air contiditioning in Houston? Can anyone give us some names of companies that have good reputations in the Houston area?

  26. Cyndi says:

    Can you retrofit to a radiator system? Our vintage house currently has radiators with no central air… any other possibilities for both heating and cooling other than ripping up floors or cutting in ventshafts for vented or radiant floor systems?

  27. shop says:

    Geothermal heat pumps (also, ground-source heat pumps or GeoExchange systems) provide both heating and cooling. They typically run piping a couple hundred feet below the earth’s surface (or occasionally connect to a nearby body of water). Here the temperature stays relatively constant throughout the year.

  28. utanma says:

    eat pumps (also, ground-source heat pumps or GeoExchange systems) provide both heating and cooling. They typically run piping a couple hundred feet below the earth’s surface (or occasionally connect to a nearby body of water). Here the temperature stays relatively constant throughout the year

  29. Anonymous says:

    Geothermal heat pumps (also, ground-source heat pumps or GeoExchange systems) provide both heating and cooling. They typically run piping a couple hundred feet below the earth’s surface (or occasionally connect to a nearby body of water). Here the temperature stays relatively constant throughout the year.