More Green Building Blog
To understand how a heat pump works, imagine using your refrigerator to keep your kitchen warm all winter. Let’s say you haul a bucket of 55° water from a backyard well and put it in your refrigerator to cool it down to 50°. Because the heat removed from the water escapes from the coils at the back of the refrigerator, you have just delivered heat to your kitchen. If you get tired of replacing the bucket of 50° water with new 55° water, you could just install a pump to circulate water to and from the pond.
With a large enough pump and a large enough refrigerator, this method could keep your kitchen warm all winter. A ground-source heat pump works in a similar way, except it has a larger refrigeration capacity and delivers its heat through ducts or radiators.
Do heat pumps save fossil fuel?
The catch is that while the heat in the groundwater is almost infinite, the electricity used to run the pump and the refrigeration unit is not. For a heat pump to actually save fossil fuel, it must deliver more heat to the house than is consumed in the process of making the electricity it uses, including the electricity used to operate the water pump.
Burning fossil fuel in power plants and transporting it through the electricity grid is about 31% efficient. If fossil fuel is burned in your home using a good sealed-combustion boiler or furnace, the annual efficiency might be about 92%—almost three times more efficient.
A heat pump that delivers 3 watts of heat for every watt of electricity it consumes is said to have a coefficient of performance (COP) of 3. This is about the level necessary if the heat pump is to actually save fuel compared to a good (not even super efficient) boiler or furnace that burns natural gas or fuel oil.
Don’t forget to factor in the water pump’s energy use
Most ground-source heat pumps are rated by their manufacturers at a heating COP of about 3.5 to 4. There is a catch, though: COP ratings do not include the energy used by the water pumps. Because pump size and electricity use varies significantly from installation to installation, it is impossible to know the COP of an actual system without measuring. But, in general, when the electricity used by the pump is added to the picture, the COP probably drops to 3 or lower, which means that heat pumps actually use more fossil fuel than a furnace or boiler.
Surprisingly, there has apparently never been a U.S. study measuring the COP of randomly selected residential ground-source heap pumps. One study that came close (“Measured Performance of Five Geothermal Systems,” NAHB Research Center, November, 1999) was prepared for the Ground Source Heat Pump Consortium — surely not a neutral party. The studied heat pumps were not normal installations: the air-handler blowers had very efficient electronically commutated motors (ECM, which in 1999 were rare and are unusual today), and the ducts were PVC pipe cemented together (almost leak-free). Even under these best-case installations, the heat pumps only managed to produce COP values a little over 3.
In other words, the best-case installations the industry could come up with barely saved any energy compared to burning fossil fuel in the building. And those measurements were for new installations; after months of use the groundwater will cool off, lowering the COP still further.
Because ground-source heat pumps probably use more fossil fuel than simply installing a good boiler or furnace, green builders shouldn’t see heat pumps as a renewable energy source. Remember, it’s always better to reduce the amount of energy a building requires than to look for a new source of energy.
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41 Comments
GSHP- costs low now, energy saved soon
Henry has excellent points that few think about. This merely points out however that no single option necessarily makes sense without detailed analysis and comparing to other options. I would claim that GHSP make sense for at least some of my clients in MN. The following can be added to Henry's points to give a full picture for at least one of my clients:
* The source fuel for our electricity in MN is NOT 100% fossil fuel so the efficiency rating is likely higher than 31%. We have (sadly in my view) a large % of nuclear in addition to coal so let's say our efficiency is closer to 40%-45%
* Detailed usage analysis for my client shows a $1200-$1500 year savings in energy costs ... yes that is partly due to rate cuts by the electric utility so after Federal Tax Credits, this client has a rough payback of 5-7 years and will never run out of propane fuel again (very frustrating in our COLD climate)
* This client plans to install solar PV to generate much of their electricity within 5 or so years. The GSHP and related Tax Credits will help make this happen sooner
Overall, this means that for some clients, a GSHP paired with PV is a very powerful and sustainable option both from an energy and financial perspective. Since PV has a relatively long payback in our region, this pairing with GSHP helps to jump that hurdle.
not apples to to apples
Henry, I agree that electricity from the grid is 31% efficient, on average, and that should be factored into evaluations of GSHPs. However, you don't seem to give fuel oil burned on site the same treatment. You assume that sealed-combustion boilers burn that fuel at 92% efficiency, but what about the energy used to deliver the fuel? Can you give us an apples-to-apples comparison?
Demand Reduction
Henry has a great point.
"Remember, it’s always better to reduce the amount of energy a building requires than to look for a new source of energy."
I tell my clients demand reduction is the best and number one priority. I often see demand reduction as never making it on their list. We provide super insulated thermal envelopes and can reduce the demand of a given home or building by 50% to 70% as common practice. This gain comes from our process alone. If we pay extra attention to windows and doors we can further reduce the demand. Everyone should be heads down focused on demand reduction.
It literally drives me crazy to see smart people install R13 batts or recycled news print into their walls and ceilings and then spend large sums of money on solar or GSHP systems. We all know traditional insulation systems are not sustainable over time. Even the newer homes we test (5 years old) are generally energy pigs and folks are not comfortable. This is easily solved with super insulated homes. Remember, super insulated homes are more energy efficient and more comfortable than a new source of energy.
A limited perspective?
Henry's perspective on ground-source heat pumps makes a certain amount of sense if you a) look only at the heating cycle, b) assume the electricity is fossil-fuel generated and c) compare only to the efficiency of fossil-fueled boilers. Not unreasonable assumptions I suppose for a NYC resident. In other parts of the country though, one or more of those parameters might vary substantially. Here in central North Carolina for example we have a/c comprising as much or more of our residential energy usage as the heating cycle. And while air-source heat pumps are the most common installation here for both heating and cooling, and while these are even less energy-efficient than the ground-source variety, Jeff makes the better point. Load reduction by focussing on better-insulated (and smaller) homes makes much better economic and environmental sense in almost any location than fretting marginal differences in source efficiency.
I'd add that as neither natural gas nor heating oil will be available for ever and, pace bio-fuels enthusiasts, scalable carbon-neutral alternatives for those fuels are not even on the horizon, it's hard to make a case for fossil-fuel point of use heating as a long-term sustainable solution.
Meanwhile renewable non-carbon sources for electricity are gaining ground fast ...
Where is the engineering??
COP is a measure of the number of units of heating obtained for each unit of electricity consumed by the heat pump. We can work out the COP at which it makes economic and environmental sense to use a heat pump (the break even point) in order to reduce carbon emissions and heating costs. At break-even point the CO2 emissions per kWh unit of gas (0.193 kg / kWh) divided by the efficiency of the condensing boiler will be equal to the CO2 emissions per kWh unit of electricity (0.432 kg / kWh) divided by the efficiency (COP) of the heat pump. Therefore, the break-even point for emissions (assuming a 90% efficient condensing boiler) is:
0.90 * (0.432 / 0.193) = 2.24 COP
Therefore, if a ground-source heat pump has a COP greater than 2.24, it will release less carbon emissions than a condensing boiler and have a higher heating output. Enclosed a chart from Department of Ecology understanding that each utility is different based on where the heat source is coming from and has a different kg/kWwh. I agree that pump energy is not included, but this effect is very small compared to the heat pump itself. Most ground source systems are in the 4.0 COP range for heating if designed properly. Cooling as noted above needs to be considered as well as the cooling from a split system used in conjunction with a furnance is normally in the 12 SEER range where a ground source is in the 20+ SEER range.
A simple comparison in WA state where energy costs are still quite low, but the comparison between gas and electric is similar:
Unit MMBtu/Unit Lb CO2/MMBtu Cost/Unit
Electricity kWh 0.003413 322 $0.075 (0.063)
Natural Gas Therm 0.1 117.08 $1.100 (0.87)
Below is a comparison of a condensing boiler, ground source heat pump, and (a third option) an air cooled heat pump producing 1,000,000 Btu of heating. All three are assumed to be producing low temperature heating water (so, for a radiant system).
Heating Technology (COP) lbs CO2 per MMBtu Heating Oprtng $ per MMBtu kWh per MMBtu Hting
Condensing Boiler 0.95 123.24 $11.58 308.42
Ground Source HP 3.2 100.63 $6.87 91.56
Air-Cooled HP 2.3 140.00 $9.55 127.39
The seaonal efficiency of the Ground Source Heat Pump accounts for ground loop pumping but is probably low at 3.2.
Conclusions:
1. Ground source heat pump is better from the standpoint of equivalent carbon production.
2. Ground source heat pump is 40% lower in terms of operating costs.
3. Energy used by the ground source heat pump requires less than 1/3 comparitively.
COP is not the whole story,
Henry,
Great Post,
I attended your session at the ACI Conference on Tall stuff, Tall Matters; Elevators, Pumps, Ventilation, and More. It was by far the best session that I attend that week.
12 years ago our Electric COOP said they would give me a reduce rate on my electric to change out our 80% gas forced air furnace and put in a air to air heat pump. So they set a separate meter and hook up the heat pump compressor, as the installer started to leave and I said how about the air handler blower fan motor that will run a lot longer now? He said "no that is on your regular metered rate", not such a great savings after all was said and done. Many verbal at play and even more profit driven motives. I am not saying that Heat pump are a bad Idea, just get all of the facts before you take a vacation with your project savings.
Some of the best ways to save energy don't have a box or sales person.
John
Moo!
Jeez Henry, you'll soon be able to upholster your entire living room set in leather with all the sacred cows you're slaughtering.
Seriously tho' thank you for the sober and well reasoned look at ground-source heat pumps. I've noticed you are getting a decent amount of criticism from the other comments, but for me I'm just happy to see lively and active discussion. It really grinds my gears when an idea or a technology is presented as being above reproach and therefore discussion, or even scholarly debate. I'm really glad you brought both this and the questionable use of underfloor heating in new construction to my attention.
Re. Moo
A big thank you to Brian Haugk for actually countering a not-totally-accurate article with an indepth review. It's nice to see actual numbers and evidence being brought together, and we're the better off for it.
The author makes a number of leaps of logic and faith, about the electricity source and efficiencies. He also disregards the full picture for alternatives. All that while making some good points, that we should compare systems based on primary energy usage per square foot, and implying that a lifecycle look is the proper look. The author did omit to mention that the 20+ year life of the average heat pump is two 10 or so year lifetimes for a gas furnace. But why get in to that....
Pumps, shmumps!
That 1999 data is gettin' kinda long in tooth, dontcha think?
The current crop of geo heat pumps typically have ECM blowers and
(ISO/ARI 13256-1) COP ratings in the 4.7 - 5.1 range for low speed
operation, and in the low 4's for full speed operation -- with an entry
water temperature of 32F (as required by ISO/ARI).
RE: pumps: The typical closed loop geo circ pump is responsible
for an 8% to 12% increase in power consumption -- and the same
reduction in COP. ...8% to 12%. Pumps, shmumps!
...BTW, how's that natural gas air conditioner workin' out for ya?
LK
geothermal
hmm a kwh in ny is 19 cents or 1.90 for 34,500 btu or 5.70 for 103,000 btu "100%" effecient
oil 2.89 for 137,000 btu at 86% effecient - 117,800 btu
since geo(cop of hydron is 4.3 but i'll use 3.0) is with well factored in has an kwh cost of 6 cents a kwh or 60 cents for 34,500 btu or $1.80 for 103,000 btu
what most people forget is the "mickey mouse" installing contractor who cant spell manual "j"
a truly engineered by a cureently trained contractor system makes all the difference - a poor natural gas system installed by the "seat of our pants". cant beat oil, or even air cooled heat pumps ---- i liken geo systems to the energy management "phase " all contractors went through. i waqs working on water cooled (geothermal) systems in the 60's till the water crisis - hmmmmm where did we get the current deluge of water ....
I'm just a student taking
I'm just a student taking thermodynamics, but I came up with some different calculations for the cost of running a GSHP with a COP of 3.0 versus a 95% efficient furnace/boiler burning natural gas. Below I calculated how much it cost to produce 100,000 BTU of heat with each option. Cost of electricity is $.107 per kWh and cost of a therm is $.79 These are Colorado's average prices.
Please correct me if I'm wrong!
Furnace/Boiler- 100,000BTU/ input required=95%. Input required =105,263 BTU. 105,263BTU=1.05 therms. 1.05 therms cost $.8295
GSHP-100,000BTU/required input=3COP. 33,333 BTU input required. 33,333BTU/(3413 BTU/kWh)=9.77kWh. 9.77 kWh costs $1.05.
Looks like its still cheaper to burn gas to me. Of course this doesn't capture the whole picture and GSHPs make a net zero home possible in cold climates if you can produce enough power onsite.
Gifford is a blind moron!
To start with, the average efficiency of a new natural-gas fired power plant is closer to 60%, not 31%. Since we are talking mostly about new construction, we need to compare new sources of energy, not antique systems serving existing homes. The average transmission line loss in the US is about 6.5%, so the net energy delivered to the house is about 56.1% efficient. Even the least efficient Ground Source Heat Pump is closer to 400% efficient, even with the water pumps included, so the GSHP is about 224% efficient with its use of natural gas. You can't even get close to that with a furnace or boiler.
Secondly, we should only be using natural gas as a way to generate electricity as a temporary means of getting past the current shortage of environmentally friendly means of generating energy. A heat pump, in itself, does not contribute to global warming, it simply moves heat from one place to another. As soon as we are able to generate all the power we need from other means, natural gas should be reserved as a mobile power source, and not squandered on providing heat and power to homes. We will too soon need all the natural gas we can find to power cars, trucks, and airplanes.
Response to Ted Clifton
Ted,
1. Please refrain from derogatory personal comments aimed at bloggers or people who post at GBA. If you continue to use derogatory language, GBA will need to remove or edit your posts.
2. You are mistaken about the COP of residential ground-source heat pump systems. The best data on these systems were published in an article published in the April 2008 issue of Energy Design Update.
Monitoring of a system in Connecticut showed that the system COP of a house was 3.5. This was for a Water Furnace GSHP that was touted by the manufacturer as having a COP of 5.0.
Data from three houses in Vermont showed average system COPs of 2.75 for three different GSHP systems. The average COPs of the installed GSPHs, according to the manufacturers, was 4.0.
The reason that monitored COPs are always less than advertised COPs is that manufacturers EXCLUDE pumping energy from their laboratory COP measurements.
electricity
The original debate was the electrical costs on a GSHP. The amount of electricity to run a air forced system or a hydronic system is not much different than a GSHP. The big difference is that all other systems use another energy form to heat and cool. Thus, the real difference. Now adapt a solar water system and solar panels and the whole thing is off-line. No heating and cooling costs even when prices rise. No CO2. Of course, a well insulated house and new vacuum seal windows and the system would reach those COP 5
Response to Harry Applin
Harry,
1. You suggest using a solar water system and solar panels (solar thermal panels? PV modules? hard to tell) for an "off-line" house. Is that the same as an off-grid house?
Neither a solar thermal system nor PV modules do a good job of satisfying space heating requirements for an off-grid house -- because there isn't much sun when you need it most, and because batteries can't store electrical energy for very long.
2. Those who have measured the system COP of ground-source heat pumps have never been able to measure a system with a COP as high as 5. COPs of 2.75 to 3.5 are much more realistic.
What about air-source heat pumps
Why is the talk just about "ground-source" heat pumps. Air source heat pumps are showing up in quantity for heating domestic hot water (what my wife calls Cold Water Heaters -- I confess, I think she's right; we don't heat hot water.) I digress. Digging these long holes like a mole run amok seems like a lot of work and entertains other problems. I am in Maine and I think I can see reasonable savings over fossil fueled heaters. But for people in sunny California, putting one in a garage (as they often do) seems like a no-brainer, eh? I have a family member in Fresno and he suffers temps in the 100's in his garage during the day which last well into the evening. Shouldn't be too hard to squeeze out some really hot water in that situation, no?
Hello,
Thank you for
Hello,
Thank you for providing this forum.
I just wanted to add some points and ask some questions.
I recently took over a house that has a ground source closed vertical loop system. The house and GSH system was built in 1990, and at that time it was, I guess, ahead of its time. The house is large, and has several heat exchanger units. Some of them are starting to fail now at 20 years. The units were made by Command Air. I gather they have gone out of business. Any idea where one can get parts? Is it worth replacing compressors?
I was advised to replace some of the units. Who makes the best units?
I did speak with a representattive from WaterFurnace, and they advised me that they expect a life cycle of 12 to 16 years on their units. I am under the impression that conventional gas furnaces can last much longer than that. Am I mistaken in that assumption?
I am wondering if these systems do require a lot more maintenance and repair due to their complexity. This does not change the energy balance discussion, but it does impact the financial calculations. I was tempted to have the system replaced by gas furnaces, and live without AC.
As they say in the tech field, "there is a leading and a bleeding edge", I am just not sure which one I am on.
Response to Anonymous
Anonymous,
You have raised an excellent point: "I am wondering if these systems do require a lot more maintenance and repair due to their complexity. This does not change the energy balance discussion, but it does impact the financial calculations."
DX systems
do the DX geothermal systems include the pumping electricity in their official COP numbers?
it seems like they would have too, which means the DX systems might run as advertised
Response to Bob Coleman
Bob,
According to the people I trust who have measured COP (Marc Rosenbaum and Andy Shapiro), manufacturers' numbers are unreliable.
I wouldn't believe any manufacturer's numbers unless they were verified by an independent third party.
DX numbers, verified?
Martin, i was sort of assuming using ASHRI(sp?) spec numbers when taking their ratings
I guess my question was, do the industry tests factor in the pumping power usage on DX geothermal systems? It is hard to read their testing spec documents to know for sure. It seems pumping the refrigerant through the ground tubes is tightly integrated into the system so i'm not sure how they'd exclude it, like the water based systems exclude the water pump which is normally external to the main system.
it seems the DX system ratings might deliver roughly as promised with the all-in-one boxes after you adjust the numbers in regard to your home compared to the standard model the testing uses
on a side note, the air source heat pumps manufacturers are not much more honest considering heating requirements, all using 45degree outside temps in the published numbers. the appliances, bodies, and dog in my house can keep things warm enough at that outside temp with no assistance ;)
Response to Bob Coleman
Bob,
I don't know for sure about the DX pumping energy question, but I agree with your analysis. It would be hard to exclude the pumping energy required for the refrigerant cycle, so I assume that energy is included in published COP numbers.
As far as I know, all of the air-source heat pump manufacturers will provide COP specs at a variety of outdoor temperatures. I know that the Mitsubishi Web site provides COPs down to -5°F, and perhaps -13°F.
mits site
yeah i saw mits posted COP numbers for those 3 mr slim models, but none of the others
using a dept of energy tool, the high HSPF for those models drops around 2.5 points which easily pushes COP numbers down towards 2. i'm assuming some of the extra features like air filtration are included in those costs which is nice if you want it.
geothermal also has that 'free' hot water
i guess the japanese use the instant hot water heaters, so mits and others don't add waste heat capturing abilities
thx again for your insight
End Use vs. Source Efficiency
Way back in 1993, the EPA release a report (Report 430-R-93-004, Space Conditioning, The Next Frontier), where they dubbed GSHPs as "the most energy efficient, environmentally clean and cost effective space conditioning system available today".
While the statement was true then, it is more true today as GSHP technology has improved in leaps and bounds in the last 20 years while combustion-based heating systems reached their maximum efficiencies year ago.
All comparisons that were made in the report were based on source energy performance which takes into account losses with all stages of energy use (including generation and distribution losses).
While it's true that manufacturer's performance data does not account for pumping energy usage (which usually amounts to 8-12% of total system energy usage, on average), equipment COPs are considerably higher than 3.0-3.5. Only R-22 equipment (which is no longer available) boasted COP's that low in heating mode.
I live in SD, which is extremely cold climate and we have many installations with actual energy usage data and can show total system COPs higher than 3.5 even after accounting for pumping energy.
Electricity generation methods will continue to improve, due in part to requirements being passed down by the EPA and also due to our desire to become less dependent on foreign oil as a nation. This fact will only improve the source efficiency of GSHPs compared to the alternatives.
The EPA report is available for download on my website. Feel free to read for yourself:
Space Conditioning, The Next Frontier (PDF)
Sidenote: DX systems do not circulate water through the ground but instead run refrigerant directly through copper coils that are buried in your backyard. There is no pumping cost associated with the system, but the compressor in the GSHP must work much harder to circulate the refrigerant through the unit itself, out through the ground coil and back. DX systems have their own set of problems to deal with and, because of the risks involved, are not predominantly used in the industry.
Our experience has been different
This article is a little dated now, but I have measured COP of my 3 ton GSHP recently and it came in at 4.3 during Dec. in 1st stage (unit was installed in 2011). The system was calculated by the installer to have an average COP of 3.9, so that calculation is a believable #, in my estimation. The EIA has an estimate on their site that the average home in NY state uses 103 MBtu for all energy used in the house. Our 170 year old home in upstate NY used 43 MBtu over the last 12 months (mainly that low due to the heat pump). We buy all our power as wind power. So I have to respectfully disagree with the blog above. GSHP's do save considerable energy on site. Depending on how the energy is sourced, it can be all saved energy. Regardless, even using the grid mix we have in NY, a GSHP in a home like mine will save energy over the other heating choices on the market.
Efficiency/Cost
I see this thread is somewhat old now, but i'll give it a shot anyway!
I am about to get rid of my old oil furnace and would love to get to a more sustainable solution than being dependent on fossil fuels. I have had a couple of contractors out to estimate installing a GSHP system at my property and I am a bit on the fence about taking the step.
I have several concerns that hopefully someone can help me with - The most important being operational cost!
I live in Long Island, New York where we pay about 21 cents/kWh! We live in a normal 1 family home from 1934 that is very poorly insulated and leaky. That i plan to fix ASAP - before anything else!
The GSHP contractors i have spoken to so far can not provide me with an estimate that seem trustworthy enough on energy consumption - I simply need to know how many kWh's i will be using to run a GSHP system in my area/house.
I had one of the contractors run me a very elaborate analysis of the house given the leaks and insulation would be done, and he came up with that the cost of running the GSHP system would be about the same as running a gas/regular AC combo system. I already have central Air and gas seem so cheap to have installed and run these days, that the cost of 30k+ cost of installing a GSHP system is somewhat scary!
How do i handle this situation? Is my electricity so expensive that it simply does not make sense in my case?
Second of all, as was pointed out in an earlier post, the quality of the installation of the system really matters! There are not many GSHP installers around so it is very hard to get good references as hardly anyone knows about this "new magic source of energy"!
Last but not least, when running oil/gas furnaces, it's very easy to get a contract for maintenance! No GSHP contractor want to provide that. When asked, one of them even said it will not be needed as it never breaks! That to me spells trouble with that particular contractor as it seems like a quick hit and run deal for him!
So i guess, all my questions can somewhat be summarized into the operational cost of running a GSHP system in my area(Greater New York/North East region of the US) and the maintenance needs/quality of a GSHP system.
I have been searching high and low on the internet and there is a lot of info out there - a lot of it is just so contradicting that i do not know what to believe!
Thanks in advance!
Response to Dennis Schindler-Thomsen
Dennis,
Briefly, if you currently have access to natural gas -- an inexpensive fuel -- there is no way that switching to a GSHP at 21 cents per kWh will ever result in savings that would justify a $30,000 investment in equipment. Don't do it.
One reason that the contractors can't estimate your energy bills is that you have a "home from 1934 that is very poorly insulated and leaky" that you "plan to fix ASAP."
The energy required to operate a "home from 1934 that is very poorly insulated and leaky" is much different from the energy required to operate a home that is "fixed." No one can know how well you will "fix" your home until you fix it.
So fix it first, and then perhaps the contractors can perform a Manual J calculation and estimate your heating and cooling loads.
Tax Credits and so on...
Thanks Martin - Greatly appreciated!
That was my worry - That it would just not be cost efficient!
But given that i do want to fix up the insulation and leakyness, and it's the same contractor that will be executing that task, which should leave me with some confidence that should the overall result be bad, it's that one contractors task to fix it... Whatever the issue is...
That being said, there are a bunch of tax credits and grants available which will bring the system initial cost down to about a third/10k-15k - Still about twice that of a Gas conversion, but more manageable. Would this still be bad choice?
I am trying to get an idea of the actual operating cost in kWh and i seem to be coming up short wherever i look. I do understand that there are many factors to consider, but there has to be some information somewhere.
Thanks again Martin - Greatly appreciated!
Response to Dennis Schindler-Thomsen
Dennis,
If you want specific answers to your questions, there is no substitute for doing the math.
You need to set airtightness goals for your retrofit work, and you need to come up with specifications for your intended insulation retrofit work. Then you need to hire a contractor with a blower door who can perform the work and who can hit the required airtightness target.
If you can do that, then you'll need to hire an energy consultant (or HERS rater) to perform a Manual J calculation (a heat load and cooling load calculation). The Manual J results can be used to estimate your annual energy bills using natural gas or electric equipment. When you have the information, you can make a decision on how to proceed.
Or you can proceed by the seat of your pants -- which is OK too, as long as you have a knowledgeable contractor. Get that house tightened up and well insulated, and you'll be in better shape. I think you'll find that natural gas will work fine for you.
Good advice!
Thanks again!
That's how i will do it! Insulate and air tighten and then decide!
Thanks again - Greatly appreciated!
heat pumps are part of the solution
I'm luke warm on GSHP in our climate (Maine) for residential applications because i think that in a well built house it is almost impossible to justify the expense here where our cooling loads are so modest. But I do like heat pumps generally and that is for one simple reason:
I can make electricity off the roof. It is easy, reliable and some would even say cheap and it happens every day when the sun comes out. No matter what I do, I'll never be able to make oil or propane, NG or even pellets off the roof..
I think of heat pumps as a renewable energy enabler, if not really a renewable energy on their own.
~Fortunat
http://www.revisionenergy.com
Energy conservation and "Grants"
We have tightened up our mini-home and cut our heat load signifigantly. We installed a Mitsubishi heat pump that has worked down to - 26C. Like the heat and cooling a lot.I got a couple of quotes on Solar DHW at $6000. Even with the $2500 grant it was not feasable. Now I found a system that would have an installed cost of $4000.. This would be realy interesting, however, the program can onl;y be accessed once, so we out of luck.Tax credits don't work for low income people.......we don't pay income taxes, just 13% of our spending on purchases and a litany of energy taxes
Need to do the math
I've researched GSHP's for years, if you want some of my math, ck our RoughDesigns.com. In short the problems with the original article are:
1. 31% is the worst case efficency for grid elec. You need to look up what it is in your state.
2. No accounting for energy used in additional refining, winter admixes, transport, via fossil fuel burning vehicles (and for natural gas, the embedded energy and carbon in pipe, continuous energy to keep the gas moving, maintaining millions of miles of neighborhood distribution, loss from leaks, big to micro, and risk of the most dangerous fuel we have).
3. Badly designed GSHP systems vs Well designed, ditto fossil fueled heating. You can't use the worst stats for GSHP and the best for the most expensive perfectly installed and maintained natural gas furnace.
4. US Military is the largest deployer of GSHP's in the world. 4,000 vertical loop GSHP's on one base alone AND the US military considers them a slam dunk in any AC dominated environment.
5. Europe, esp. Sweden is heavily dependent and betting heavily on GSHP's to meet their much more ambitious climate goals (than ours). Same laws of physics there as here.
I've been in the alt. energy world for 30 plus years and early GSHP - using off the shelf equip for cooling office buildings, hooked up to ground loops based purely on theoretical math were disappointing. Like my hair, those times are long gone. Variable speed GSHP's in a well designed system will produce COP's of 4 plus. RESEARCH your installer, pick one whose clients KNOW there systems are working as advertised. GSHP is slam dunk for new buildings now, and if you can re-use your internal distribution efficently, for retrofits.
One last comment - Elec can and is being produced via wind and solar, distributed across the grid, lowering transmission losses, cheaper every day (see my website for how fossil fuel pricing is fixed to it's benefit) and these are the ONLY easily expanded green energy sources we have.
Geothermal Heat Pump Systems
The benefit to heat pumps due to geothermal water heat load is the higher suction pressure due to higher load temperatures (ground 55F). This will provide most of the benefits especially at lower out door temperatures. Also beneficial, if VSD condensing fan (evaporator) is used then the lower fan speeds (possibly no fan at all) are possible not to mention not having to use the coil defrost. These benefits will exceed pumping losses for cycling the water.
Response to Andrew Cole
Andrew,
No one is denying that ground-source heat pumps have definite advantages over air-source heat pumps. The problem with ground-source heat pumps is that the equipment and installation costs are so high that these systems are hard to justify for a single-family house.
ARTICLE POSTED ON APR 6 2009 BY HENRY GIFFORD: GSHP
Yes this is an old thread, but still worthy of comment!
Another way the opening statement could be worded is: A properly designed & installed GSHP's will save home owners energy, but may not necessarily save the grid any energy. A qualifier than could be added such as: The total energy requirement to operate a GSHP's is dependent on the efficiency of the grid and how well the GSHP system has been designed & installed. More useful information could be added such as: As an electrical grid becomes more efficient the inputs at the power plants decreases, which ultimately means we all can operate our light bulbs, fridges & GSHP’s… on less resources. Also adding wording such as: reducing a power plants use of carbon based fuels increases the positive environmental impact of using GSHP's. Such wording allows readers to better understand the problem isn't with the GSHP technology; the problem is with inefficient carbon based electrical grids!
With all due respect, the author has made a potentially misleading (because its one scenario based) claim in the article as follows:
" But, in general, when the electricity used by the pump is added to the picture, the COP probably drops to 3 or lower, which means that heat pumps actually use more fossil fuel than a furnace or boiler. "
This statement can be true, but not necessarily true. It’s not true where I live. It depends on how carbon intensive a homeowner’s electrical grid is and how efficient it is. If the grid is totally carbon based and runs at 30% efficiency and the COP's of the GSHP's are as mentioned then yes, a GSHP could use more fossil fuel than just installing a boiler (however A/C hasn't been taken into account which is much more efficient using GSHP technology than traditional condensing units, which again favors GSHP's again)
The carbon intensity of grid energy can vary greatly from place to place. So I think it’s important for this website to point that out to the readers along with the fact that the problem here is with electrical production NOT with GSHP technology. That's not to say 'in the end' there may be jurisdictions where from strictly an environmental point of view it’s better to install a boiler (if you're not putting in A/C). But builders and homeowners should understand where the problems are so their choices are made with a more full understanding of the situation.
Then there's the whole issue of operating costs of GSHP's vs everything else, which is a different topic from Energy Savings & Environmental Impacts.
I think it’s also worth mentioning that GSHP's have had a wide range of results from around the world, varying from: excellent in terms of money saving because GSHP's can be the least expensive way today to heat a home in areas that don't have natural gas, to poorly performing systems that don't work properly. My own system has a SCOP of 3.6 on 2nd stage in the fall and is at 2.9 on 1st stage in the spring. SCOP (System COP) includes everything! Pumps, blower & compressor. I live in Ontario Canada and from midnight last night to noon today my grid electricity was only 9% carbon based.
see http://canadianenergyissues.com/2013/09/12/carbon-content-of-electricity-some-cross-jurisdictional-comparisons/ From midnight until noon today the total ‘renewable energy’ content in my grid electricity was 30%.
In terms of the present low cost of natural gas keep in mind that natural gas been 300% higher in cost at times over the past decade compared to today and it’s not controlled like electricity prices.
The key to determining whether to go with a GSHP or not strictly based on cost alone is to determine: 1) the quality & quantity of your ground energy 2) have your GSHP sized correctly 3) have the heating/cooling distribution system designed & installed optimally. 4) find a qualified contractor to do all this 5) look at the payback based on installation cost and assume an inflation rate of grid electricity to be at the rate of inflation plus 1 or 2 %. Give fossil fuels the same rate of inflation, admittedly this future price guessing is just that, but what else can one do? No one knows the future cost of anything. However a more certain thing will be the ability of a homeowner at some in the not so distant future to generate and store a portion or all of their own electricity cost effectively on site. This is why I installed my own GSHP and that’s what I explain to my customers when giving them suggestions on all the heating & cooling options available (which I also sell).
In terms of GSHP's being 'Green' & operating on a 'Renewable Energy Source': my system is very 'green' due to the small amount of carbon based electricity I get from the grid. In terms of my GSHP using renewable energy, I presently (late October) put one unit of grid electrical energy into my GSHP and get 2.5 units from the ground on 1st stage, which means I get a total of 3.5 units of energy for every unit I put in = SCOP 3.5 on 1st stage. I get a SCOP of 3.6 on 2nd stage. In the spring I get 1.9 units of energy from the ground for every one unit of grid electricity I put into my system on 1st stage, which again means I have a SCOP of 2.9. In the spring I get a SCOP of 3.1 on 2nd stage. The difference in SCOP’s is due to the lower ground temps in the spring. The main alternatives for me would be oil, propane or electric resistance for heating as I don’t have natural gas in my area. When I calculate the BTU replacement cost over the winter for my GSHP using electrical resistance it’s 330% more, propane is double and oil is 250% more using the ‘latest & greatest’ products that compete with GSHP’s. So in my case a GSHP saves me a lot of money and it’s very ‘GREEN’! Yes natural gas would cost about 40% less than to heat my home with compared to my GSHP. But it’s not an option for me and natural gas wouldn’t give me any decent A/C. I produce much less green house gases using my GSHP to heat my home with compared to using oil, propane or natural gas (even if NG were an option). People in the HVAC business that are doing well and know a lot about GSHP’s and live in areas without natural gas or if they have land, they tend to choose GSHP’s. Why do think this is so? It’s because of the year round comfort and the cost effectiveness and in my case it’s also because of the ‘green factor’! And yes my payback is much shorter than most whom have installed a GSHP because I helped with a lot of the installation and because I’m in the business.
Its true GSHP’s are not for everyone. However if you live in a rural area without natural gas and you’re building a new medium or large home, or your renovating a medium to large home, then it’s a ‘no brainer’!
Many installers are under qualified and don't understand or don't bother to investigate some of the items I've listed above, which need to be investigated and discussed with customers. Also all those Government grants that encouraged many people to install GSHP's have also encouraged many under qualified contractors to get into the business too quickly due to the increased demand for GSHP’s. GSHP's require much more thought & knowledge to install successfully compared to traditional HVAC systems and as a result there are systems that aren't functioning correctly. However there are many people very happy with their system. So the again, the two biggest problems with GSHP’s are: contractors with insufficient knowledge and from an environmental perspective, inefficient carbon intensive electrical grids. There is nothing wrong with the GSHP technology. In fact it just keeps getting better. Variable speed compressors are here!
Ray Mueller B.Sc.
CS Energy & Mechanical
Response to Ray Mueller
Ray,
Thanks for providing a response to some of Henry Gifford's arguments.
Since this article was written, the economics of ground-source heat pumps for residential applications has continued to worsen, while the economics of air-source heat pumps (especially ductless minisplits) has continued to improve. These days, it's really hard to justify the installation of a $20,000 or $30,000 GSHP system, when so many builders are successfully heating homes with two ductless minsiplits, at a cost of $6,000 -- and when these air-source heat pumps have a system COP of 3.
For a further discussion of the economics of residential GSHPs, see Are Affordable Ground-Source Heat Pumps On the Horizon?
Homeowner's POV
I'm considering a GSHP - as a CPA, be sure I ran the numbers! It's a harder sell when you already have access to natural gas, but I still found that the GSHP is less expensive over time (even compared to a high efficiency gas furnace). What set me back is the common argument that you're just transferring the direct use of fossil fuel (gas) to indirect use (electricity generated by fossil fuels). That really hit me when I compared the annual kWh to run the system to my kWh requirements just to run the lights, appliances, etc.- i.e the proposal cited kWh usage more than double that of my current needs. That said, I took the kWh needed for even the most efficient gas furnace (by converting the Mcf into kWh) and the amount of kWh used for the GSHP is FRACTIONAL. I haven't made my final decision yet and I'd really welcome some thoughts on this - especially since I'm really trying to compare apples to apples. I'm finding that when you translate everything into the same unit of measurement (kWh), the geo really makes sense.
Just a touch of background - the basic design of my existing home isn't conducive to modifications to create passive solar - and since most of my home is made of logs, there's only so much I can do to tighten the envelope.
Does anyone have thoughts they can share on this situation?
Thanks!
Yet another thing that has changed a lot since this article was written - the externalities for producing cheap natural gas. These days, it's most likely fracked. Which means both groundwater and surface water contamination. Then there's the gas that leaks while drilling, during well operation, and from the distribution system. The most recent determination I can find says methane is leaking twice as fast as was believed two years previously. Methane is believed to be about twenty-five times more potent than CO2 as a greenhouse gas. That's taking into account that methane's lifetime in the atmosphere is much shorter than CO2's. As with oh-so-many things, almost none of this is figured into the price of the 'clean' natural gas we buy. It's all someone else's problem. Namely, ours. We will live with the result - like it or die.
https://www.sciencemag.org/news/2019/07/major-us-cities-are-leaking-methane-twice-rate-previously-believed
Roger,
While Henry Gifford may have been comparing ground-source heat pumps to natural gas in this 2009 article, GBA does not promote the use of natural gas for space heating. In general, most GBA authors advocate all-electric homes, so the better alternative to a ground-source heat pump would be an air-source heat pump.
That's good to hear. Lot's of true believers in "natural" gas, in my neck of the woods.
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