Anyone here use a geothermal (ground-source) heat pump as your primary heat source? Or know anyone who does and how it works out for them?

Wondering about things like operating costs, routine and not so routine maintenance, etc..

Looking at it for a new house build.

ETA: Western PA.

I don't have one, but I have studied green, high performance, and energy efficient construction to obtain certification as a green real estate appraiser.  

They can be either sourced for a well or from a long series of loops of pipe (pex typically) buried in a trench.  The goal is to reach a stable temp source to displace heat into, or remove cold from.  They operate under the same principle as a conventional heat pump.  Warmth is extracted from the outside, or expelled to the outside.  However, since they do not have the same exterior compressor they run quieter.  

They are much more costly to install due to the installation of the ground source.  In my area of South Carolina, a typical residential heat pump costs $8-15K installed based off size, efficiency, and quality.  I have a larger high efficiency heat pump and the installation without duct work was $12k.  The lowest price I have heard for a geothermal heat pump in my area is $25k, with most installations north of $30k.  The majority of the costs will revolve around the ground source type.  A well installation is more expensive than a trench.  Since the

There are government subsidies for geothermal that vary by area.  They can reduce the costs by as much as 50%, so you will want to check with the installers in your area.  They will be well versed in how to get the subsidies and rebates.

The monthly operating costs typically run 50% or less than a traditional heat pump.  

Additionally, a geothermal heat pump can also be used to make hot water, which can further reduce monthly utilities.  

It will take a long time to pay back the initial ground source costs.  However the ground source is generally a once and done sort of deal.  So if the interior equipment does expire, you generally have a replacement cost that is similar to a traditional heat pump.  You can expect 15-25 years out of the above ground components.  The ground source will only need repair if the lines are cut by something like a backhoe.  Even in the trench installations they are generally buried 3 feet or more down depending on the frost line in your area.

Not sure what area the OP lives in because that will change the payback time. However, in my Zone 4 area, I looked at ground source heat pumps and ended up with a conventional system. There was no way to get the payback time realistically. I think as a general rule, you are better to put the money into insulation.

In my case, we insulated heavily and installed a dual fuel air source heat pump with a propane furnace in our 2650 sq ft house. Our cost for AC runs us about $20 per mo in the summer and electricity for the heat pump and propane in the winter cost vary from $30-50 per mo (combined heating electric and propane costs). If we saved 50% by having a ground source heat pump, the payback time would be forever. Remember, if your ground temp is 50*, an air source heat pump running at 50* outside temp is actually more efficient than the ground source heat pump because the ground source heat pump has to run the pumps to move the heat transfer liquid around. So, ground source heat pumps are cheaper to heat and cool with for sure but you have to know how much you’ll really be saving to know if it will pay off.

I’d rather put in a cheaper heating and cooling system and spend more in insulation than to insulate like the standard for the area and put in an expensive HVAC system.

Now those numbers would change if the house was unusually large or if you were retrofitting an older, hard to insulate house.

In my Zone 4 area, I wouldn’t even consider a GSHP unless I was building a house well above 4000 sq ft. If I lived in a colder climate that number would likely change.

just put a heat pump in at mom n dads to replace geothermal system. their monthly bill went down and the house actually stays cool in the summer. their system was 8 years old and nothing but expensive repair after expensive repair. Never will I ever recommend those junk science systems to anyone.

Sounds like an improperly installed system. They aren’t “junk science”. They actually do work when installed correctly. Many are not installed correctly.  I know of a government building in my area that uses multiple wells for the buildings GSHP. The building is something like 25,000 sq ft and from what I recall, the utility bills are impressively low considering the size of the building. The wells were drilled below a parking lot.

All good info but I think this part, while well-meaning, is a bit misleading, and likely factually incorrect.

#1 Your comment about increased energy use due to circulating the fluid in the loop doesn't take into account the fact that an air-source heat pump (ASHP) has a fan to circulate the air through the heat exchanger and also doesn't take into account the more efficient heat transfer when using a liquid medium.

Point of reference my circulation pump on my 4-ton GSHP is 1/8 hp. What is the hp of the fan on a 4-ton ASHP? Probably at least 1/2 hp...

#2 I know you're trying to provide an apple to apples comparison using the 50 degree air temp comparison but that is misleading because the thermal/heating load on a house is very low at a 50 degree ambient. Compare the numbers at 20 degree ambient and it paints a drastically different picture.

I agree, either improperly installed or poorly designed system.



I have a water furnace, installed in 2008. I bought this place in 2016. The only maintenance I've had to do was occasional flushing of the loop (twice now since we've been here) to ensure there are no blockages, air bubbles, etc and replacing of filters. My unit is a 2-stage compressor (new ones are likely variable speed inverter driven).

Likes: I didn't have to pay the install cost, it is low maintenance, not noisy*, gets me a property tax break, and is affordable to operate.

Dislikes: It doesn't allow me to use renewable resources for heating in the winter (working on getting a wood boiler going to supplement heating for that reason).

*Ours was retrofitted into the house. The old furnace was in the crawlspace, the Waterfurnace wouldn't fit so it was placed in a bedroom closet (taking up the entire closet). A GSHP has the compressor inside the unit, all a single unit. Being that it's in a bedroom closet, sitting in a traditional wood-joist & sheeting floor, near the bedrooms, a low hum can be heard any time the compressor is running. I can hear it humming away right now, I'm 20 ft away. I recommend you place it in a dedicated utility room, away from the living area, preferably on concrete to reduce the sound transmission.

Things you should know: they aren't cheap to install but they can benefit in the long run. They are not a substitute for good insulation. The more you spend on insulation the longer it will stretch out the payoff/break even point but it will still be a net gain in monetary savings. As already stated, the source (well or closed loop) is generally a 1-time expense and doesn't need replaced which decreases future system costs to similar levels of other HVAC systems, meaning your initial break even is longer but after that it will be shorter.

AC works great.  Heat struggles.  Would not do again.  My neighbor has the same issue.

Sorry, forgot to mention originally. Western PA. It can certainly get into the negatives here, but not often and usually not long.

Also, I will be supplementing with a wood burner, may have two.

In a new house you need to set targets for your insulation and air tightness performance and you need to get buy in from your contractor or you will never hit it.

Insulation is pretty simple because it should be on the drawings and inspected.

Air tightness is a little more difficult because you'll need to do a blower door test before sizing your heat pump.

Generally speaking, the tighter the better. You can run a duct fro your air handler to the outside to get outdoor air, you don't need it coming through the cracks.

My experience has been pricing out GSHP systems, and they are ridiculously expensive compared to a good ASHP.

You can get a single speed water furnace, or you can get a variable speed ASHP with spray foamed metal ducts (less than 10 CFM in duct losses) and still have money left over for air sealing and windows.

Looks like you're in zone 5.  If I was in your position, I'd use a conventional system and insulate heavily.  If you have natural gas available, use that.  If not, then a dual fuel heat pump/propane system is ideal....especially if you plan to have wood burning stoves inside the house.  

Unless you plan to build a very large house, if you insulate well, it's very unlikely you'll get the ground source heat pump to pay off.  Insulation pays off the life of the home but even a GSHP will have to be replaced eventually.

My numbers are calculated on my $ .10 per KWH.  If you have much lower rates than I have, then a GSHP will pay off sooner.  

A GSHP will take a much larger generator to run than a gas or propane furnace if you want to be able to run it during a power outage.

I was curious about that.

One thing we liked about the GSHP option was our whole house would be electric. I know electric rates are likely to go up (just like everything else), but we figured you need electricity to run a conventional gas system too. So basically we'd be reducing our overall needs to keep the place running if shortages arise.

There is natural gas available at the road, but it would be over 1000' to the road, and that's assuming we could make it a straight run, through the woods, down into a small valley, under a creek and then back up to the road. Our builder thinks we should do that. I'm pretty hesitant to take that route. Think I'd rather have a propane tank right at the house if we were to have gas.

Electricity rates rise a lot more slowly than fossil fuel prices do. I can see having propane for a back up but you wouldn't need it much of the time.

One of the upsides to all electric with heat strips is that the heat pump and the heat strips can be on at the same time, so if the heat pump is providing half the heat at a COP of 2 and the strip is providing half the heat at a COP of 1 your blended COP is 1.5, whereas the most efficient propane heat is going to 0.96.

At $0.10/kWh you are getting electricity for the equivalent of $2.70/gal of propane, but you are using less electricity than you would propane to produce the same amount of heat.

You get “free” hot water only in the summer time when the AC is on. In the winter, you may need a backup heat source. Most GSHP systems are not sized to provide 100% of your heating needs, too expensive. So they are sized at 90-95% of your heating needs. Granted, this ways 10 years ago when I was learning to size geothermal systems. Tech may have changed since then.

I don't know what your propane costs are for your area nor do I know how much an air source heat pump would run in the winter vs a propane furnace for your area.  In my case, we don't use a lot of propane (thanks to the heat pump and the high R value insulation) so if natural gas was even available, it would actually cost more than propane due to the high meter rental costs in my area so at least check into that.  Some places are lower than others.  1000 ft seems pretty far to run a gas line at your expense.  In the previous house we built in town, the gas company quoted me $9000 to run the gas lines a few hundred feet.  Propane wasn't allowed so we ended up all electric.  It did what we needed it to (heat and cool us) but I hated an all electric house and won't go back to one willingly.  

Your wood stoves should help you keep your heating costs lower during deep cold snaps if you did decide to go the dual fuel route assuming you have a good source of cheap hard wood.

It takes a large generator to run any heat pump.  It takes a pretty small generator to run a furnace.  With a dual fuel system, you get the benefits of cheaper heat when it's not too cold outside and the warmth of gas heat when it's very cold outside.  Plus, you don't have to run the heat pump in a power outage.  Just run the propane furnace.  

For years natural gas was considered to be the most reliable utility.  I think that opinion changed for a lot of people last winter.  During the deep freeze we had last winter, a lot of places were pleading with the public to reduce their natural gas consumption because the system was at the breaking point.  At least in my area, nothing has changed in the natural gas supply to the area.  The issue is, for most winters, the area has plenty of capacity.  But, if we have another deep freeze like we did then, we might not be able to get enough natural gas to fully heat our houses.  

With propane, if you have enough storage capacity, you know you have enough propane to get you through the cold snap.

So why did you hate the all electric house?

On the firewood, we'll likely have all we can cut/need.

I dislike cooking on an electric stove compared to gas or propane.  I don't like having to have a grossly oversized generator just to have heat.  Heating with electricity is expensive particularly with a regular heat pump system with back up electric resistance heat.  An unpleasant side effect of heating with a conventional heat pump is a phenomenon known as "dirty sock syndrome".  Basically, your heat pump has to defrost the outside and in the process, runs as a regular air conditioner briefly until the outside unit is defrosted and then it switches back to heating.  The problem is, you'll get a little moisture on the coils and then they heat up...but because a heat pump doesn't get hot especially when it's cold outside, you get bacteria buildup on the A coil.  It doesn't hurt anything but it stinks.  Cleaning the coil helps but it always comes back.  With a dual fuel heat pump, when it switches the heat pump off and runs on the furnace, super heated air blows across the A coil and then into your ducts killing any bacteria on the coil.

With propane, you can store your own BTUs. You can't realistically do that with natural gas or electricity.

We have a propane water heater and a heat pump water heater.  The heat pump water heater does most of the work but the final heater before entering the house is the propane water heater. I can have hot water without needing power (aside from running the well pump and that doesn't take a very big generator for me while an electric resistance water heater uses at least 4500 watts.

Sounds like typical bad sizing/installation for heat pumps, they size for cooling design day without realizing that heating design day calls for a larger capacity in climates that get below 40ish. It’s all about the delta between inside and outside. 100 degrees outside vs 70 inside is a delta of 30, but if you get to 20 degrees then you have a delta of 50 between that and an inside temp of 70. So you would have to size the unit for heating capacity, not cooling, and this is very commonly done wrong.

That being said, ground-source is not worth the trouble in most cases. Inverter compressors and variable refrigerant flow have revolutionized heat pumps, and if you have the capability for dual fuel - natural gas or propane as a backup - I’d never go with ground-source heat pumps, pretty much ever. Another plus is any decent HVAC tech can work on your heat pump - not so with ground source, and it adds unnecessary complexity.

Some of the new mini-splits are still heating down to -10 degrees, you just have to make sure you size it correctly. Obviously it’s not as efficient when it’s that cold, and they may not be ideal in climates that are below freezing for much of the year. Ground-source has its benefits but they are way over marketed and oversold.

Quick rant on GSHP design: dropping the ground loops under a parking lot in a region that gets hot for extended periods of time is pants on head retarded. The asphalt absorbs heat and bakes the ground below, just like the ground loops are doing as they reject heat from the building, and over time it dries out the ground and the loops lose capacity. This can be mitigated somewhat with sprinklers or a high water table, but doing it as a matter of course in dry soil raises my blood pressure. I see it all the time on commercial ground-loop systems, and they almost all have problems even often during the construction phase. Many add cooling towers to the system within a few years, all because the design was garbage.

I should have read the whole thread first. Mostly ditto to ColtRifle as he is spot on with a minor correction: variable speed compressors, air handler fans, and refrigerant flow have changed the game. You can run a variable speed air source heat pump at a restricted capacity(often configured at the thermostat, or at the logic board) off of a generator without issue, and the slow ramp-up of the compressor means you don’t need the hard-start amperage that standard compressors require.

I far prefer cooking with gas, also, too. With dual fuel propane and variable speed heat pump, along with wood stove backup, you’ll be all set. It’s the way I would go, at least.

Parents had one put in about 20 years ago and the only problem they had was the pump went out and was so old they had to get a new system.

Works well when hot and cold, but if you are used to forced heat (propane, NG, wood, etc), then the heating cycle will take some getting use to.

They heat/cool a 3600 sqft house for around 80-100 per month.

That’s a great point, and could be why the builder recommended running the gas line.

I had geothermal in my house in Johnstown pa.  Had about 6500 sq ft.   3 zone system.

Electric bills I'm winter we're 5-600.

Make sure you have enough deep wells drilled, we had 16 at 185 feet.

Only issue I had in 10 years was a control board went out.  

The Equipment room in basement required a dehumidifier I'm the summers or things sweated.

My building at work is heated with that way.  I believe it is the only state owned building heated that way.  It is currently broken again just like every winter since 2010 when the building opened.  It is getting replaced with a traditional boiler system in the Spring.  Ours uses injection wells and will blow them out at times.  We have no heat in our building so it sucks right now.  I think the closed loop systems would be a better bet, but I would run away from pumps, water and shit.

At minimum check the cost of running the gas line to the house as further data for cost comparisons.
I had my meter upgraded from a 1/2” line to 1 1/4 to accommodate increased demand at 0 cost to me but was only 350’
They had a form I filled out to anticipate the future increased demand for which created a credit which fortunately fully covered my cost.
Best thing I did when I built the addition was spray foam, high efficiency hvac units & switching to the ga power program called smart usage lower my power bill. Basically power is $$$$ June-September 2-7pm plus a demand charge ,but rates are cheap all other times. With the spray foam I can shut down AC at peak time and coast to 7pm where systems restart. Dryers & water heaters are nat gas.

Strange how every contractor we talked to about repairing the system said to shit can it. No one recommended salvaging any single part of that trash system. Pumping good drinking water 250' out of a well running it across a heat exchanger to cool refrigerant then pump it out to the creek out back is pants on head stupid. I won't get into the idiotic valence radiant cooling and heating trash that the previous owner also bought into based on "green energy" promises that came with the geothermal crap. Good luck finding an expert on these geo systems as well. There were 2 contractors in the entire area that would even look at the system. One came out and replaced a control board. The next problem they had that contractor would not come out due to not having enough technicians to cover gethermal stuff. So my parents got stuck with an idiotic excuse for a tech. that was a parts changer from the other company. 8 year old system that had $7k in parts changed.

I have a drinking water well that is being put in for free. I was intending on using an open loop heat pump for my new build.  We are in the country and can only get electric or propane.

2700 sqft house. In zone 7. Lots of humidity and cooling needs.

Are we coming to the conclusion that open source heat pumps are not worth it. My monthly heating/electric rates are about $300 a month now in an 1800sf ranch and that doesn’t include cooking with propane.

What's your point?  The system was incorrectly designed?  We don't doubt you.  An improperly designed system won't work properly.  Nothing surprising about that.  I'm not a fan of geothermal for most purposes because in my opinion, for normal sized houses it won't pay back....definitely won't pay back without the taxpayer funded subsidy.  That said, as I mentioned, a large house in a severe weather area it may well pay back eventually.  For most normal people, it'll probably never pay back.  An improperly designed/installed system will NEVER pay back.  

The fault is not the geo thermal system....it is an incorrectly designed system.  Not all geo thermal systems are bad even if some are installed incorrectly.  The science is sound.  In practice, the expensive system won't always be worth the expense.

North Carolina has climate zones 3 and 4 and a tiny section of zone 5. Zone 7 is a small section of the US and is up north.  

99% of the time someone talks about climate zones in this subforum they're talking about USDA plant hardiness zones. Considering USDA zone 7 covers part of his state he's certainly talking about those zones, not the zone map you posted.

Except in this thread we aren’t taking about growing anything we are talking about heating and cooling….which is what this map is for. Probably should be on the same page when we are discussing heating and cooling. I’ve never seen a heating and cooling person use a USDA planting map when discussing HVAC systems.

Which is all irrelevant to the point I was making. You're not making yourself look like any less of an ass by spouting off at me. It was obvious what he meant, you were being obtuse about it and now your pride is hurt because you were called out on it. You do whatever you want but you're not helping your case.

I have no idea what you are talking about or why you are all offended.  But, it doesn't really matter to me.  Hopefully the OP gets out of this thread what he wants to know.

Interesting. I am still in zone 7-8 in regards to the USDA planting zone. I never knew there were different climate zones.

The map I posted is what is used nationwide for heating and cooling design and calculations. I’ve never seen anyone or heard of anyone using the USDA maps for designing heating and cooling. As you can see, if you were to ask someone to do a Manual J heating and cooling load calculation and used the USDA map, you would get an incorrectly calculated Manual J load calculation and end up with incorrectly sized equipment.

A properly designed and installed geo thermal system will work well and will save money….but the savings might not be enough to justify the expense. Most of these geo thermal systems being installed nationwide would never be installed if the taxpayers weren’t subsidizing them.

IM any time, no worries.

On topic for the thread, here’s an article I just found with a quick search on Mitsubishi Hyper Heat. The big draw for geothermal was its ability to continue to heat and cool during extreme conditions, but now the juice may not be worth the squeeze. Mitsubishi states 100% heating capacity to -5degF, and 70% heating capacity to -13F(click on the links in the article).
Mitsubishi Hyper Heat Feature Review

The article is not very technical but it shows how they work, and keep in mind other manufacturers have similar technology so you have options. Essentially they can vary how much the refrigerant circulates and the speeds of the indoor and outdoor fans to wring out all the heat and efficiency possible. I’ll repeat myself though, it’s all about the sizing. Inverter heat pumps don’t solve all problems but they are far better at heating than they used to be.

Just keep in mind that heating down to X temperature doesn't equate to heating efficiently. COP & EER are measured at specific ambient conditions that can make air source heat pumps appear to be just as good as geothermal. But with air source heat pumps the COP/EER drops the further away from that magic temp you get. The COP for heating in cold climates may actually be only a tiny fraction of that of a geothermal system.

Additionally, most manufacturers list the minimum ambient operating temp as the temperature at which the COP=1 (the same as electric resistance heating).

EER is calculated at a 15 degree temperature delta (95 outside, 80 inside). But if you like to keep your house 70 degrees when its -10 outside that's a 80 degree delta. EER at those conditions will be a fraction of the test conditions. Geothermal will not experience that drop bc the thermal exchange medium is the liquid in the ground loop or well which is going to be around 50 degree delta under absolute worst case scenario (loop is running below freezing) but more often around a 20 degree delta.

I’m well aware, except you really need to read up on the new technology, including at least Mitsubishi, Daikin, and LG, which all have low-temperature options. The Hyperheat claims 2.2 COP down to -5degF and 1.89 COP down to -13degF. Keep in mind, with geothermal you also have to compare hydronic pumping energy plus the efficiency of the geothermal heat pump compressor itself, vs the inverter mini split with no hydronic pump and a much more efficient heat pump compressor, among other things.

It gets complicated quickly, and again it’s been stated by myself and others you really need to start with a good design. I am not an engineer, for what it’s worth.

Submittal to the hyperheat unit mentioned in the linked article and where I got the COP ratings:
Hyperheat Submittal

Just for the record, I'm not trashing air source heat pumps. I actually have 3 of the Mitsubishi hyper heat units (12 kBTU) and I'm very happy with them. I just want people to be aware that there are some differences. I honestly don't know what my geothermal system's COP is, but it would be disingenuous to compare my 14 year old geo system to current ASHP offerings. I don't know current offerings but I think it's a bad assumption to assume that GSHPs cannot make use of the same technological advancements the hyper heat and other units use. A quick numbers search on the current GSHP offerings from the manufacturer of my system show COPs as high as 7, where the Mitsubishi you provided the data sheet for tops out at 4.54. And I'm certain the GSHP COP won't fall as quickly as the ASHP because of the source of the heat.

Lastly, I pointed out several responses above that ASHPs also have "circulation" energy. The energy to run the fan on the outdoor unit is the equivalent of a circulation pump on a GSHP. Often the fans on ASHPs consume far more energy than a circ pump.

All good points. What it often comes down to is economics, too. I’ve seen people compare $10k for a high-efficiency ASHP vs nearly $40k for a GSHP due to the drilling requirements(not everyone has room for a shallow field). I was only trying to illustrate the potential alternatives to GSHP, which ASHP does a much better job now than in the past.
I’m not trying to trash GSHPs, either. They are awesome technology especially in extreme climates, they just take a lot more design care than the typical rule of thumb design so often seen in residential work. IF, a big IF, you have a properly designed AND installed GSHP it can be a great experience. You’ll want to make sure someone local can service it, too.

I used to work for one of the largest Water Furnace dealers in Ga. We also serviced Bosch and sold a small amount of them. I would never buy one just due to the high upfront and high repair cost on the back end. It will save electricity if you have a well designed system but a high end 20 Seer system from Trane or Carrier will have damn near the same operating cost based on my conversations with owners. Most seem to do well with zoned ductwork.  Very few mainly Bosch owners said they would buy them again. Installation being done properly is critical. We used to perform a lot of repairs in a neighborhood that had a shared loop and iron fittings were used to save money. The rust even with water treatment killed pumps and required a filter to be added to keep the systems running.