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Green Architects' Lounge

Ground-Source Heat Pumps, Part 3: Five Questions

For the last part of this Green Architects' Lounge podcast episode, Phil and Chris play "Five Questions" with two professional heat pump installers

A concentric well is installed for a closed-loop system.

I sent an email to Jeff Gagnon and Jim Godbout, and asked them five basic questions about ground-source heat pump installations. In this part of the Green Architects’ Lounge podcast, Phil and I take some time to review and compare their answers. We also take a moment to touch on the subject of ozone-depleting refrigerants. Finally, Phil shares a song by the Brooklyn band Here We Go Magic, called “Collectors.” Be sure to check out Parts One and Two of this podcast to learn the basics of ground source heat pump installations and rules of thumb for well depth expectations. Ready to play “Five Questions” with the pros? Then come on down!

1. When is a house a good candidate for a ground-source heat pump system?

Jim: A large home with very good insulating values.

Jeff: A) Under new construction, a home is almost always a good candidate for a geothermal system, especially if the homeowner is financing the construction project. The increased mortgage payments are offset by the savings in fuel. Therefore, it is “cash-flow positive from day one.”

B) In retrofit applications, it is a great candidate when the equipment in the home needs to be upgraded anyway, or if the homeowner is considering installing a cooling system or simply would like to get rid of their dependence on foreign fuel oil.

2. When is it NOT a good candidate?

Jim: Older home, poor insulation, existing high-temperature hydronic system, existing steam system, due to the amount of infrastructure work required.

Jeff: A) Geothermal is not a good candidate under new construction when the lot size is so small that the setback cannot be maintained to septic tanks and the leach field, or if the ledge is extremely far down. Sometimes this is related to a lot of added expense.

B) Geothermal is not a good candidate for a retrofit application when:

• There is not adequate space for ductwork.

• There is not a low-temperature radiant heat distribution system.

• The basement is finished and there is no attic.

3. What’s your preferred way of doing a ground-source heat pump system (e.g., open loop with radiant slab distribution)?

Jim: Closed-loop concentric high-producing well with water to air using ECM technology circulating pumps and fans for most homes, providing heating and air-conditioning with radiant in the baths and kitchen.

Jeff: Our preferred way of doing a ground-source heat pump system is open loop, using either a ducted or radiant heat distribution system.

4. If I called you up out of the blue and said I have a well-insulated 2,500-square-foot three-bedroom house and I’m thinking of going with a ground-source heat pump, how much is that going to cost me?

Jim: $40K to $50K, with an operating cost around $900 annually for heating and air-conditioning. That is figuring in pumping cost.

Jeff: A 2,500-square-foot home would cost approximately $20,000 to $25,000 for air, and about $25,000 to $30,000 for radiant. This would be approximately a 4- to 5-ton geothermal system. The well and pump system would cost approximately an additional $10,000 to $12,000. If you had to drill a well anyway for domestic water, then you would already be spending $6,000 to $7,000 on the well, in which now you could combine the two.

5. What is the thing that is most often overlooked—or rather, what surprises the clients or designers?

Jim: Design of geothermal is not taken very seriously by many installers. More than half of the listed installs in the state of Maine have problems with performance and operating cost due to poor choices. I know; we get the calls.

Many design systems with electric resistance backup heaters, so this means when we most need heating, they are using the most expensive way to heat the home in Maine, at 15 cents a kilowatt.

Our company will only install closed loop systems that require no electric backup. Some of the larger systems we install use peaking condensing boilers, which also help with large hot water demands.

Money should be spent on the building envelope in almost every case that is brought to me asking about retrofitting geothermal to an existing home. There is no sense in heating the outdoors with ground loop systems, especially at 15 cents a kilowatt. Many parts of the country and Canada pay 6 to 8 cents, which makes it much more attractive.

Jeff: We try not to overlook anything! We use a job information sheet so that on each project we have adequate information before we begin a design. However, I would say the bleed or water discharge location may be the most common unknown. This is because we don’t even know if we need bleed until the well is drilled, etc.


  1. GBA Editor
    Martin Holladay | | #1

    Very helpful
    Thanks, Chris and Phil.

    And thanks to Jim Godbout for his honesty. I think he's right -- these systems are usually costing $40,000 to $50,000. It will take a LONG time for fuel savings to pay for that much equipment.

    So, designers, remember: it's all about the envelope. If there is anyone in New England building a home with double-pane instead of triple-pane windows, then you're not yet ready to call up a ground-source heat pump installer.

  2. aj builder | | #2

    my numbers
    Last project:
    $10,000 95% condensing hot air, a/c system
    $18,000 OC spray foam insulation.
    $1800 fuel costs guesstimate at this moment
    Adirondacks NY location

    I think in the near future we should be able to install systems that cost much less than prices in this blog.

    $5,000/1000sqft is the sweet spot for me anyway.

    I am working on a daytime high temp air to water heatpump solar set up. Others like the idea of improving upon the very inexpensive air to air wall heat pump units.

    $20-25,000/1000sqft is too expensive.

  3. GBA Editor
    Martin Holladay | | #3

    Low-cost heat and AC
    AJ Builder,
    I like Carter Scott's solution in Massachusetts. He built a 3-bedroom, 1,232-square foot home. The installed cost of the heating and cooling system (including AC) was $5,500. He used a Mitsubishi Mr. Slim ductless minisplit unit -- one outdoor unit and two indoor units.

    Here's an article:

    The house was sold for $195,000. The price included enough PV to make it net-zero-energy. It produces enough electricity to balance out its heating and cooling costs -- as well as its entire electrical load.

  4. aj builder | | #4

    best post in weeks Martin
    Thanks for your post... I am very willing to copy great work of others.

    The day is coming that we all will be able to afford to be net zero.

    Then we can focus on net plus!

  5. Andrew Henry | | #5

    Making it simple
    Martin indirectly points out something that bears repeating over and over!

    A great many options and solutions open up when the designer has done his best to reduce the home/buildings heating/cooling demand?

    Everything is simpler if the load (demand) is small.



  6. Christopher Briley | | #6

    That is a good post, Martin
    That house and article is a nice breath of fresh air. High quality, net zero construction is not often found below the $300k mark and it is down right scarce below $200k.

    A big take away from this series is that the economics of ground source heat really make sense for the larger, well-insulated homes, or perhaps for those who insist on radiant distribution, or share great skepticism for air to air heat pumps in a cold climate. But otherwise, they are expensive.


  7. 78bjAFnoVt | | #7

    I work for a builder in New York State and Jim's Estimate is a bit high. For a 4.5 ton system I bid 30k even. And thats for a vertical direct exchange unit.

  8. wjrobinson | | #8

    Clarify price Shawn
    30k not including any rebates or subsidies? If so... you are getting closer to numbers that make sense to me. The other problem I see is no one truly gets 3x resistence in performance. I would have to see the utility bills for a year along with room temps data to believe someone's numbers. I think 2x is the norm and 3-5x is extremely rare but doable.

    A well built structure with 95% condensing natural gas system combined with a heat pump A/C will use the same energy as a ground sourced heat pump and do so for half the install cost.

  9. Christopher Briley | | #9

    direct exchange
    Shawn, did that include the well? and I notice you said "direct exchange" dose this mean your refrigerant from the heat pump unit gets circulated to the well and back? In part one, we touched on this, but Phil and I have no direct experience with such a system. Does this type of system offer greater efficiency?

    AJ, both Jim and Jeff get COPs of around 4 with their systems.


  10. aj builder | | #10

    COP of 4.... still may be hiding some costs
    COP to me is a lie. If I install electric baseboard heat.... COP is really 1. Now a ground source heat pump says COP 4. What is not included from what I read is, the electric for circulation motors. And more.... How would Jeff and Jim really know their COP's? I know of no accurate way to measure heat output of a heat pump. I do like their stated annual bill of $900 but would like to know how that is arrived at, do they put meters on the entire HVAC system load? Would be nice to know the details behind their numbers and then I could be a believer. (Price still is annoying though)

    Very easy to fudge numbers in the building and HVAC world. Especially dislike the R value discussions that are meaningless when just talking R values of uninstalled products.

    Keep looking into heat pumps Chris... we all need more affordable solutions.

  11. GBA Editor
    Martin Holladay | | #11

    Response to Christopher and AJ
    Few researchers have measured the installed system COP of GSHP systems. To calculate the system COP, you have to include measurements of pump electricity use.

    I know of two researchers who did this: Andy Shapiro in Vermont and Rob Aldrich in Connecticut. I reported the results in the April 2008 issue of Energy Design Update.

    Rob Aldrich measured the performance of a Water Furnace system. The manufacturer claimed a COP of 5.0. The measured COP of the system including pumping energy was actually 3.5.

    Andy Shapiro measured the performance of three GSHP systems in Vermont (2 Water Furnace systems and an Econar system). The three systems had an average nominal COP (as claimed by the manufacturers) of 4.0. The measured COPs for the three systems averaged 2.75.

    Conclusion: to estimate the in-service COP of a GSHP system, take the manufacturer's advertised COP and multiply it by a factor ranging from 0.70 to 0.74.

  12. aj builder | | #12

    Thank you Martin
    Again, you think like I do Martin. Real facts are needed to make real decisions.

    Marketing always employs semi to ridiculous truths so as to favor one's desires.

  13. Jim Godbout | | #13

    I don't ever Blog but Chris Briley asked me to answer this question on COP

    We do have an engineering firm that calculates COP named Turner associates and a gentlemen named Jeff Harrison who has done great research and calculations on heatpump systems including pumping cost associated with system.
    This knowledge from Jeff harrison has specifically driven my company to only do closed loop concentric systems with very high COP.
    This allows the end user a palletable payback period with virtually no maintenance cost.

    You can lose 1 COP just in pumping cost of open loop system.

    Water Furnace Envision with concentric designed systems have been in the 4-5 range

    If you introduce solar to the closed loop COP can go over six in this style of Hybrid system.

    In any case Geothermals cap cost are very significant if you want it done right.


  14. Christopher Briley | | #14

    Thank you Jim
    That's two beers I owe you.


  15. Jeff Gagnon | | #15

    Response to reviews
    Hello All,

    So it seems I am a little bit late with feedback to all. However better late than never.

    I typically do not blog nor have the time. However, I can tell you that COP's are very measureable, When lower COP's exist, it is typically due to some of the following. Improper sizing of duct work, lower entering water temperature from well, high entering load water temperatures, Improper pipe sizing, or improper control wiring etc. I don't believe the engineers make them up. I believe they are true under the correct operating parameters.

    Also, Geothermal is not just for large well insulated homes. IF a BTU produced cost X. and you can create a BTU for 300% less than X, than it makes sense in any home. I agree that it makes sense to focus on the building envelope as a number one priority. Though it does not mean you need ICF, spray foam Insulation, SIPS, or Dense Pack Cellulose in a 5000 sq. ft. home for geothermal to make sense. That's just crazy.

    I have a 1700 sq. ft house and a 2600 sq. ft house right here in my home town that tell me there electricity bill is Appx. $ 70.00 a month in Jan. & Feb. I also have many, many others alike. For example, the 1700 sq. ft. home costed 20K. the well cost was 10K. So they spent 30K all together. If they would have installed a hot air heating system with cooling they would have spent 14K plus another 6k for the well and pump system. so for 10K more they have a heating system that costs them $ 70.00 a month in Jan. & Feb. My point is that this is a small house....

    Hope all this info. is useful. I am going to go home and watch the patriots beat the Jets now!!!

  16. GBA Editor
    Martin Holladay | | #16

    Response to Jeff Gagonon
    You wrote, " it does not mean you need ICF, spray foam Insulation, SIPS, or Dense Pack Cellulose in a 5000 sq. ft. home for geothermal to make sense. That's just crazy."

    I'm not sure what you mean. But if you are implying that builders who install dense-packed cellulose are crazy, I would have to disagree.

    First, get the envelope right.Then you might find you won't need a $30,000 heating system.

  17. Brian O' Hanlon | | #17

    I listened to it last Friday in semi-awake state. I'll give another listen though. These are a really great trio of podcasts I feel. I have some comments to make on the recent restaurant discussion with Wolfgang and co. When I get some time. I want to point out though, that in Europe a huge amount of work goes into a parallel process to 'design', which is known here as 'Cost Planning'. You don't have Cost Planning 'professionals' in the US, like we do in the European system. But it should be noted that 'Cost Planning' processes now work at a very intimate level with quantities involved in construction - and the 'quality' of those materials, labours and processes. It has occured to me, since I began a full time course in this 'Cost Planning' professional, known as 'Quantity Surveying', that a huge amount of work goes into this. And it makes no sense whatsoever, for energy budget calculations to happen separately. It would represent for me, a colossal doubling up of labour at the design and development stage - at least in Europe. This point has not much to do with geothermal equipment, but I wanted to give out this brief flyer - for what I hope would be a more thorough thesis, if I get the time. It occurs to me, that as the United States goes for better and more accurate energy budget calculations - you may consider combining that effort with a move towards the Cost Planning technique. I think we have to be really careful though, where Cost Planning is already established in places such as Europe, that we do no upset existing professionals, by introducing another calculation method in addition to the existing one.

  18. Christopher Briley | | #18

    on behalf of Jeff
    I'm pretty sure what Jeff is saying there, Martin, is that he doesn't feel that those advanced (for lack of a better term) forms of insulation are necessarily a prerequisite for a geo-X system if the house is large. He's saying even with standard insulation a geo-X system would present an immediate economic advantage over other common systems. I'm putting words in his mouth here, but I know him and his opinions on such matters pretty well.

    That's not to say, of course that you shouldn't improve the envelope, because we all know that would be a very effective thing to do.

    Brian, we do have cost estimators, who are hired on the owner's behalf to basically deliver a reasonably accurate opinion of cost. They typically do exactly what the general contractor would do in the first few weeks of bidding a project, they call up suppliers and subcontractors, and rely on their own experience to render a good estimate. They are not always used for commercial projects, and are rarely used for residential projects and I've never known one to to run 'operating costs' or energy consumption analysis, they are focused (like the general contractor) on the construction cost only. I think there is a fantastic opportunity for a new form of company here in the states as 'value engineering firms' but the problem is, no one will ever hire them until a project is in crisis, then they'll wish they hired them at the beginning. Brave indeed, will be the company that establishes themselves as such a company. But man, if they could estimate construction cost, operating cost, perform energy audits, and commissioning, AND LEED administration. They'd be pretty cool dudes.


  19. Brian O' Hanlon | | #19

    Chris, as I said, I did do up a longer draft having read the dinner conversation between yourself and members of the American Passive house community. So when I get a chance, I will look into writing that up properly. The Cost controllers here in the British system have similar status as professionals, to what the architect would have in north America and Canada. While in north America/Canada, the cost controller would be employed contractually by the architect or engineer. I.e. The cost controller is a 'service provider' to the designer, and it is the designer who must bear responsibility for the cost plan, as a duty of care to their employer. Over here in Europe, the designers generally do not carry that duty of care, and would not know even how to handle it. Which is very bad. Hence, it leads me to believe, that designers here in Europe find it difficult to accept their duty of care to the employer, to manage the energy budget, as well as the fiscal budget. So because of your familiarity with that responsibility for management of budgets in north America - it didn't surprise me, to hear you talk about apps, which link between PHPP and Sketchup etc. I remember suggesting this ten years ago, in an architectural firm in Ireland, and I was very quickly shot down. That was when the office here moved towards an early BIM software, MicroStation J Triforma. Of course, AutoDesk BIM and ArchiCAD is becoming popular here now. But again, it is a tool which was developed for the north American context. Here is Europe, BIM software is readily embraced by designers as a means to visualise and coordinate to a certain degree. But they hardly ever look at it from a fiscal or energy budget point of view.

    Cost Controllers in the UK/Ireland have their own indpendent professional status within the construction industry - and they do protect that territory. Simply put, they will not cede it to designers easily. They enjoy a direct contractual link to the employer, unlike in north America. The adding of a burden of care on the energy and Co2 budget side wouldn't be a major issue, for European cost controllers. The best way to think about the European cost controller, is like a gourmet kitchen. Hardly any waste leaves the kitchen. The by-product of one operation, is used to fuel some other. Basically, they glean 'cost analysis' from previous jobs, which enables them to offer 'early cost planning services' directly to the client on future jobs. That is where they make their margins. In other words, they buy their information wholesale and sell it on at retail rates direct to their employer. The large cost control firms here have huge databases, which serve as their kind of proprietary black box of cost information, which spits out very accurate answers for proposed work. So, I could easily see them applying the same gourmet chef approach to energy and Co2 budgets, as they currently do to fiscal budgets.

    The best way to think about 'value engineering' is, as being the flip-side approach to what I described above as 'cost planning'. There are issues with value management/engineering for sure. Who takes ownership for the changes that arise out of that process? But the point to bear in mind, is that Value Engineering thrived in north America, because you did not have an earlier tradition of cost planning which competed with it. Does VM or VE mess up the original contract for 'design' between the employer and designer? These are questions that one needs to be aware of. The VE, or VM approach is finding its way over to this side of the Atlantic, from north America and Canada. It could be that Cost Planning similarly will move over to you. If I get time during the hols, I will try and present all this thesis more clearly.

  20. Brian O' Hanlon | | #20

    One more point
    Another analogy to think about, in terms of the European cost planning approach - is the designer has his pistol fitted with a lazer scope. Which helps to get the general aim right, and then pinpoint the cost target to within single digit percentage figures of what the final tender will be. From what I can gather so far - this comes about, because European employers of construction professionals tend to get annoyed if tenders bids arrive back at figures, that are different from the cost plan target. If the tender bid arrives back higher than the cost target, they want to know why. If the tender bid arrives back lower than the cost target, they are equally annoyed. Because they tend to claim, they could have found a better plan for the monies which they will now, not need to spend. Hence, this analogy of the lazer scope I use. Given that 'context' in Europe in terms of fiscal budgets on projects - I often wonder, how employers here will behave, when we start to work seriously with energy and emissions targets/budgets/final totals. You see?

  21. Brian O' Hanlon | | #21

    Lazer scope
    Another analogy to think about, in terms of the European cost planning approach - is the designer has his pistol fitted with a lazer scope. Which helps to get the general aim right, and then pinpoint the cost target to within single digit percentage figures of what the final tender will be. From what I can gather so far - this comes about, because European employers of construction professionals tend to get annoyed if tenders bids arrive back at figures, that are different from the cost plan target. If the tender bid arrives back higher than the cost target, they want to know why. If the tender bid arrives back lower than the cost target, they are equally annoyed. Because they tend to claim, they could have found a better plan for the monies which they will now, not need to spend. Hence, this analogy of the lazer scope I use. Given that 'context' in Europe in terms of fiscal budgets on projects - I often wonder, how employers here will behave, when we start to work seriously with energy and emissions targets/budgets/final totals. You see?

  22. Robert H | | #22

    Chris - Insulation vs geo

    You used the term economic advantage. But is geo first an economic advantage when you weigh other options. To me it makes more sense to make sure the home is air sealed and insulated with "advanced insulation". Yes there would be a reduction in energy costs/use with a geo but in an economic sense that does not mean it is the more cost efficient alternative.

    With "advanced insulation" you would reduce the cost of wells and equipment. On top of that you would use even less energy and thus the daily operating cost would be reduced too. If weighed, the 2 options of more insulation, smaller geo vs less insulation and larger geo I think the more insulation option wins out.

    Other factors to consider with more insulation are comfort, durability of structure, air quality, etc. A geo system will not cure hot or cold rooms. Air leaks bring in a lot of dirt, pollen etc as well as transport moisture in to areas that we want to keep it out of.

    Geo's lower temp of heat can make an under insulated home feel uncomfortable. I know someone who added a geo unit. I had advised him to insulate and air seal but the geo salesman told him how much he would save and it wasn't necessary. He has lived with the system for 2 winters now and complains that when we get those extremely cold period that the unit runs alot and he feels cold. After he spent so much on the geo and has since retired he doesn't have the money right now to fix the house. I have convinced him insulating and air sealing will help him. After that the question is will the geo be the right size to operate correctly and efficiently. BTW he has had the installer and someone else come out and check the installation, it is reported to be operating correctly.

    I think doing geo first creates a disincentive for adding more insulation and air sealing. Either people feel that they have done all that is needed or that it is to costly after they have spent so much on a geo.

  23. GBA Editor
    Martin Holladay | | #23

    Response to Robert H
    Thanks for your post. You can join my small group on this side of the fence, where the crazy people congregate.

  24. Christopher Briley | | #24

    I totally agree
    Hey, I'm on that side of the fence too!

    Step one, work with the sun and site. Step two, reduce energy demand (seal, insulate, protect). Step three, deliver energy efficiently... hey wait Alex Willson just went through all of this didn't he?


  25. aj builder | | #25

    lets do the numbers
    $72/mth gets me 2200btu/hr w/ COP 1.

    So at system COP 5, GSHP we get 11000btu heatload for stated months Jan/Feb. And without special insulation (same as my home).

    I can't heat my 2000ft home to 72*F with 11,000btus/hr in Jan.

    I have read that COP 3 or less is a real number.

    If my needs are 35,000btu/hr at COP 3 then my Jan electric bill would be $370. I would have to double my COP to 6, and half my btu needs by huge insulation and weatherization retrofit to get down even close to $70....$92.50 if all is done, which is still 28% more!@!

    I am back to needing utility bills in my hand and a personal tour to understand $70 utility bills for a home like mine in January heated to 72*F via a GSHP and no wood heat supplement.

  26. aj builder | | #26

    google ad... LOL
    300,000btu/hr 97% efficient wood boiler!!!!!!

    I could heat 10 homes all at once in my neighborhood.

    Gotta love marketing, capitalism, the US of A and such!

  27. GBA Editor
    Martin Holladay | | #27

    More GSPH bids
    Here's an article on a green home under construction. Two different contractors bid on a ground-source heat pump system: "Geothermal was way too expensive. Two contractors bid about $70,000 each for a vertical well system."

    Read more here:

  28. Dennis Kihlstadius | | #28

    Suns angles for passive solar
    Is there a web site for determining the proper angle to set a house facing south in northern MN? I am planning to build a home using the suns rays throughout the house with interior glass upper walls. The home I live in now was designed for the Minneapolis area and the sun does not work like it should. I am 250 miles north and am adjusting the blue prints of my present home. [email protected] Thank you for any and all answers to this question. I am also wondering about closed and open Geothermal heating for the same house. Is it over kill? It was just over -20 below F for four nites and more coming this weekend.

  29. GBA Editor
    Martin Holladay | | #29

    Response to Dennis Kihlstadius
    Check out the free software available here: Sustainable By Design.

    "Our premiere solar design tool is SunAngle, a shareware program used by people around the world since 1995 to calculate solar angles based on location, date, and time."

  30. Jacob_D | | #30

    Curious how this article holds up for folks? One of my takeaways from this piece is that ground source is only worth it if you have a good envelope. Is that still the case?

    I have a leaky 50 year old home that I'm slowly attempting to seal up. As a side question, how can you tell if your home's envelope is good enough to make geothermal worth it? Does something like [Home's Efficiency Score]/[Cost of Ground Src Heat Pump] exists?

    1. CarsonZone5B | | #31

      not well, see Martin's excellent article from a few months ago. The gist is that air source heat pumps have gotten so efficient that it's generally not going to be worth the installation cost for ground source unless you are building out a lot of housing that could use one source. I actually don't follow the reasoning behind needing an energy efficient home in this old article, in fact the less energy efficient a small home is the more a more efficient heating source would be able to recoup its cost.

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