For anybody in TVA's electricity networks (mostly: Tennessee): they offer an annual promotion to single-family homeowners only to purchase an $1800 AO heatpump waterheater for only $250.
Maths: 85% discount on fancy new waterheater, which also dehumidifies and cools your house (passive result of heatpump).
TVA usually offers this promotion between Thanksgiving and NYE. You can order online from HomeDepot, or walk into a local store [0]. This ends up costing LESS than a new traditional resistive-type heater.
[0] either method: they DO verify SFH (by more than just ZIP code) -- duplexes and contractors not authorized/allowed
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My own $250.00 "TVA homeowner special" (as a licensed electrician):
<https://i.imgur.com/4wCez9u.jpeg> this specific design draws from both bath and bedroom [dual 6" inlets], exhausts into kitchen [single 8" outlet] | utility closet is only 5ft x 4ft (~20sqft)
Don't forget to use a pressure regulator, expansion tank (coldside, only), & (preferably) a sediment filter. Whatever you do: do NOT use a water softener before the tank.
Interestingly, TVA/EPB/Lowes [7] never asked for our swaps (I threw all four oldtanks away).
[7] not Home Depot; AOSmith -eligible, not Rheem (can no longer edit abovepost)
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Didn't know about the gas disqualifier... or the great URL/reference (thanks)!
For future TVA homeowner installers: the website seems to indicate that you MUST use an approved contractor for the rebate — at least December 2025, in EPB/Chatt, this was not required: just had to go to Hixson Lowes and have them look up address and then paid (w/ delivery, not in-stock).
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Less than a decade ago, I helped install a 38kW [•] tankless/instaHot heater (¡¡¡ that's three 240v40a two-pole circuitbreakers !!!) into a beautiful new home. Homeowner is actively doing his part not maintaining the unit in eventual hopes of justify purchasing a new heatpump waterheater.
Godspeed.
[•] I think technically it's 28kW -rated (there's a consumer-installed limit, w/o boilermaker license), but the circuits support more w/o 80% derating applied
> I think technically it's 28kW -rated (there's a consumer-installed limit, w/o boilermaker license), but the circuits support more w/o 80% derating applied
A tankless water heater is not considered a continuous load so there’s no need to apply the 80% rule.
A 60A 2P breaker will have a trip curve that results in a thermal trip for just under 100% of rated current in around 2-3 hours. The fast acting part of the trip curve is magnetic, longer duration trips are thermal.
The trip curve on page 25 of the pdf applies to Square D QO plug-in (residential breakers are usually plug-in, commercial are bolted on) 2-pole breakers rated 120/240V from 45A-60A. Find the 1 (times rated current) at the bottom and follow it up the chart until it intersects with the black area of the trip curve, that is approximately when the breaker will trip at 100% of its rated ampacity. Look at the left hand side to see the time in seconds that it will trip in.
It’s hard to see exactly where it intersects, but it’s somewhere between 7000-10000 seconds, or 2-3 hours.
So, you need to apply the 80% rule to continuous loads because breaker trip curves are adjusted so the thermal overload trips in 3 or fewer hours at 100% of rated ampacity. If you look at .8 times rated load, the line never intersects the trip curve.
Here’s a manual for an A.O. Smith tankless water heater:
On page 10, the 4 element, 7kW per element unit draws 58.33A per 60A breaker, 7000/240 = 29.167A, two elements a piece for 58.33A per 60A breaker.
It’s lot cheaper to wire up a 28kW electric heater if you have 480V three-phase, it’s only 28000/480/1.732 = 33.68A, all you need is a 35A 3P breaker, three #10s and a #10 ground.
240V single phase needs two 60A 2P breakers, four #6s and two #10 grounds, or if it was a single-point connection, one 125A 2P breaker, two #1/0s and a #6 ground.
The 28kW limit is from the Boilermakers Union, not ours [IBEW] =P
As much as I hate AFCI breakers, I do love a well-designed "stupid" heat-response timeout that's in compliance with the NEC. You're correct that residential waterheaters are not "continuous loads" – had slipped my mind.
I used a tankless/instahot heater (and helped install a few hundred in the early 2010s) and am so much happier with my hybrid/heatpump tank-type (it is so much cheaper to operate, requiring a relatively minimal upkeep of: an annual drainage).
Plus: there are no "miminum flow" requirements/bullshit, which results in some tempermental dishwashing among the water-conscientious (sp?).
> The 28kW limit is from the Boilermakers Union, not ours [IBEW] =P
Ahh gotcha, they must’ve pushed for some good ol trade protectionism after electric boilers came out and high-power tankless water heaters are within their wheelhouse or something like that. I wouldn’t consider it a pressure vessel but I don’t blame them for scooping up the work, lol. I’m not in the union myself, but I do manage IBEW electricians and know enough to be dangerous ;)
> As much as I hate AFCI breakers, I do love a well-designed "stupid" heat-response timeout that's in compliance with the NEC. You're correct that residential waterheaters are not "continuous loads" – had slipped my mind.
I believe electric tank style water heaters under a certain size are considered continuous loads, but tankless are not.
> I used a tankless/instahot heater (and helped install a few hundred in the early 2010s) and am so much happier with my hybrid/heatpump tank-type (it is so much cheaper to operate, requiring a relatively minimal upkeep of: an annual drainage).
Plus: there are no "miminum flow" requirements/bullshit, which results in some tempermental dishwashing among the water-conscientious (sp?).
Heat pump water heaters seem amazing, 25% of the power usage of a resistive heater, and especially for $250!
I wasn’t aware of minimum flow requirements for tankless heaters, I suppose it’s necessary to prevent overheating/steam or something? I mostly see tankless water heaters as part of emergency eyewash station installations, most commercial buildings around here either use boiler water for domestic hot water heating or have point-of-use tank water heaters near sinks/bathrooms.
I have a heat pump hot water heater, and it's been awesome. It's ROI has definitely improved with all the energy price spikes. It's located in my garage (I live in Florida) so there's no shortage of hot air for it to use.
Same — I maintain four (one RHEEM and three AO's).
The AO is a much cleaner/simpler/nicer install. The Rheem stupidly requires duct adapters (for small-space, <700sqft "closet" installations). AO won't last as long, but at $250 who cares?!
This reduces electric infrastructure demand, which is why it's subsidized. Presumably, this saves money (duh) for the company (duh) and possibly the customers (presumable duh). Presumably people who care about the planet understand this.
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Running a single heatpump waterheater is the equivalent of not driving your car, annually, according to TVA (in carbon footprint).
I'm running four [two households, ten people]. What's your question?
Corrosion will destroy the tank's fittings/liner. Quickly.
So quickly, in fact, that it is mentioned multiple times in the installation manual to not do lots of things (no salt-fed softeners in bold/red/all-the-things).
Curious about this because I thought the entire point of a water softener was to prevent damage to appliances due to mineral buildup. I’ve never heard before that the salt is bad for any appliance.
While this may be true (have no knowledge | how does it work w/o salts?), the OEM will immediately void your warranty if you use any sort of homeowner water softener, per both Rheem and AOS installation manuals.
I have both; mine are warranted "platinum|10yrs" — why chance it?
Absolutely. Not just because of the heat, but because large parts of Tennessee are subtropical rainforest (~60+" annual rainfall) so dehumidification is absolutely essential. Why not get free dehumidification from heating water?
Installing an air-exchanging heatpump OUTSIDE?!? is absolutely a massive waste of energy in such a climate (and many more).
>isn't noise an issue?
All four of mine are installed in 20sqft utility closets, using insulated ducting to top-wall registers (also, insulated). For my first install, only, I used a solid metal 90° to pierce the wall/inlet (this one is loudest, basically as if the wall weren't there).
Granted, there is definitely a "louder" side (the inlet-sides), but not by much. None of my utility closets are insulated (from surrounding draw rooms), and the entire unit isn't loud enough to justify more than just a layer of sheetrock on both side of the wall/partition.
If this was installed in a garage, it would definitely be known-to-be-on, but not aggressively-so (if you have a workbench outside, e.g.). I don't know the decibel rating, but it's about the same loudness as a stand-alone dehumidifier (same wattage/concept, actually), without walls.
Should you desire the quietest install, insulate the wall (between studs) and use dual 6" insulated ducting, with switchbacks, for both inlet and outlet (that's a lot of hardware). In such an unnecessary installation, it would be whisper-quiet.
A heat pump could win as the best HVAC technology, though a better drilling for ground-sourced ones. Just a shallow drilling (up to 100m) that works in retrofit mode, such as drilling from the basement, would be a great upgrade:
- No outdoor unit that looks awful in many settings
- works well, even in the coldest winter, without a spike in electricity usage, COP 5
- very reliable with long durability
- super quiet, no ambient noise
- 20% more efficient
Currently, drilling is very disruptive in retrofits, but there is progress in compact techniques that might change the equation.
Yeah, not worth it in most cases, but when things line up, it is the best.
I've built 3 houses and got a bid on ground source heat for each one. I finally pulled the trigger on the 3rd house because we:
1) Moved where it was quite a bit colder, -20F for a week is common.
2) We have enough land to trench only 6'/2m deep to bury the loops instead of drilling like we would have needed to do on the first 2 houses.
3) There was a tax credit on it
4) No equipment exposed outside
Absolutely love it and it will make it difficult to move away when we want to down size b/c we'll pay more in utilities for half the space.
We also have some air-source on an addition I built, I'd use it anywhere that was slightly warmer than where I'm at.
That depends on climate. The longer and colder your winters are, the more you benefit from the reliable efficiency of a ground source. Ground source heat pumps have been the most common choice for heating new single-family homes in Finland for the last ~20 years.
Installation is probably relatively cheaper there due to volume too. In areas where it is less common, there is less competition and fewer options for competent installers.
Yeah, recently saw some numbers for air-to-air vs air-to-groundwater, and it break even after more than 25 years, with more than twice the initial cost
Bingo. Literally abandonded in Lithuania, air to air is so much cheaper. Some builders even ditch hp altogheter - basic electric underfloor heating + solar panels is so much cheaper.
I'm in New Zealand and my bedroom heater is $20 electric + $20 smart plug + $10 temperature sensor. Winter bill is ~$100 NZD. It would take ~20 years for heat pump to recover install cost alone.
To jakozaur’s point, there’s plenty of reasons drilling can get cheaper and there’s at least one other company working on it [1]—would love to hear about others! I’m a minimally informed amateur but my intuition is that the way it’s typically done (multiple inch borehole, U-tube geometry) is fairly suboptimal since the diameter is a lot wider than you need it to be just for hydrodynamic resistance and you get losses from the outgoing liquid cooling the incoming liquid. Dropping the diameter should make drilling a lot easier—-you can sink a 5/8”x12’ ground rod with hand tools in the right soil! (you’d still have to figure out how to make the holes meet up but I imagine there are ways of doing this).
The fact that you need to roll out a drilling rig plus crew at all is going to be a large part of that cost. For it to become interesting for the average homeowner the price is probably going to have to drop by something like 75% - but that basically kills any margins for clever new innovations...
In some potential future, there is an engineered a plant/fungus in a pot that you place onto the worksite. Months later, with regular sugar-water and hormones, it gives you a root-pipe for pennies a day.
Of course at that point we might not need the cheap pipe in the first place.
What I was trying to get at with the ground rod example is it’s entirely possible that you wouldn’t have to roll out a drilling rig and crew. To zoom about a bit, the main risk for heat pumps is really ugly winter peaks but besides that, ASHPs are perfect 90+% of the time. So the main role I see for GSHPs is backing up ASHPs to shave that peak, and once you scale back their role like that it seems like there’s a lot of ways to cut installation costs significantly.
We have a ground-source heat pump for our ADU. We did it because we were curious about just how efficient we could make the house, but I don't expect that it will ever break even financially vs a modern air-source system with resistive backup in our climate (northern New England, typically very few –20˚ nights, –10˚-0˚ more common with daytime highs in the single digits).
It works great, but it's hard to see a way to it making sense for most folks here.
The solution is of course to get a communal system. As a bonus, drilling one giant loop is significantly cheaper than drilling hundreds of smaller ones.
It doesn't work this way. Dense cities just don't have enough space for geothermal heating. It really works for single-family homes only, or maybe just a slightly more dense areas.
Not to mention that city infrastructure is WAY too expensive to build, anywhere. You'll spend more money on planning than on doing the actual construction.
Ground source heat pump owner here in the US. The original system was installed in 2007, and the loop field was designed to "best knowledge at the time". Well in the 20 years since then, NREL changed guidance on how far apart and how deep loops need to be installed. Rightly so, because our circa-2007 is "short looped", it's not sufficient for the house loads, but there is nothing we do about it other than putting on more expensive pumps, more expensive antifreeze and live with heat pump compressors dying pre-maturely because they are working at their design limits. All this makes it as expensive as traditional system (and if we tried to go net-zero with solar, the amount of solar required (because it runs so inefficiently) is larger than our roof area.
So I'm looking at a backup gas boiler to take load of the heatpump/ground loop (house has radiant heat).
And they are not quiet. 5-Ton water to water compressors are not quiet.
And the control system (HDX) and amount of expertise required to keep the thing running is a major barrier to getting low cost maintenance.
Maybe a 2026-designed system will work better and actually live up to the hype you talk about, but there are decades of poorly designed and discarded ground loop heat pumps that have "poisoned the well" if you will.
Does the ground source heat up (or cool down) over time, making it less effective? The deep ground is very well insulated, which is why after a century of operation the London Underground is 10 degrees warmer. I wonder whether GSHP users need to balance their load by (say) consuming more heating than they actually need in winter so that summer cooling remains effective.
I think there are two types of this, only have experience with 1 so far. Within a single season, absolutely. In deep winter entering water temp (EWT) is around 30degF (this is a pretty accurate measure of bulk ground temp). Typical for where I live is 50degF.
Other type is permanent change that persists year over year. Haven't lived here long enough to measure this. But if you pull more heat from the ground in the winter than you put back into it into summer (we use a water to air compressor for AC in summer), then yes, it can happen and does happen. Don't know if we are in this bucket yet.
Out of curiosity, has the demand stayed the same? I'm asking because you see the same with electricity grids, designed in a different time with much lower demand.
Sorry to hear this, it seems like a great system to me but you have to have the capacity right. I'm planning on getting one in the next year but the drilling will be more than we need and we opt for no glycol (yet) as that also gives us headroom
I don't think system ever met demand when commissioned (we are 3rd owners). 1st owner largely neglected the system (which I interpret as reaction to it not working well), 2nd owner had local company known for "fixing geothermal" do a lot of retrofits (new higher flow pumps, increasing diameter on plumbing within the utility room to decrease "lift/work" required of the compressors, more feedback sensors / logic boards, added backup electric water tank heating for the radiant system, switch to methanol). These fixes have seamed to limit failure modes to a smaller set of things: mainly compressors dying early.
Currently system is running 20% methanol to combat the 29degF EWT (entering water temp) in deep winter. House is in Zone 6a.
One thing I learned in researching all of this is that use of ground source over many years can move the bulk ground temp permanently. (House also has water-to-air water furnace for AC). If heat pulled from ground in winter is not sufficiently replaced by heat added during summer, can move bulk ground temp over time. (If densely packed residential ground loops ever became a thing, I think this is a real risk.). But I am not sure if we have this issue at our place, still in first year, not enough data points.
If you're an individual with an apartment you don't have the choice to drill.
If you're building the apartment building you have the choice to drill for the entire building, and the number of units that benefit mean this is much more cost efficient than with single family homes.
In DACH, there's not really an alternative for many homes. Heat pumps are by now cheaper, more efficient, more versatile and definitely greener than other means of heating.
If you get one, just make sure to get the dimensioning right. They are WAY more complex to plan, install and maintain than traditional heating.
>[heatpump waterheaters are] WAY more complex to plan, install
Only if you place them within <700sqft (for a typical indoor residential location). Only in areas smaller will you need to duct them, somewhat similarly to:
<https://i.imgur.com/4wCez9u.jpeg> this specific design draws from both bath and bedroom [dual 6" inlets], exhausts into kitchen [single 8" outlet] | utility closet is only 5ft x 4ft (~20sqft)
As an added bonus it'll passively dehumidify/cool whereever it drafts to/from.
> They are WAY more complex to plan, install and maintain than traditional heating.
I'm curious what about them would be more difficult to plan, install, and maintain. Obviously there are many things to consider when retrofitting a building with a central gas furnace... but otherwise why would they be much more complicated than an air conditioning system?
I've had a lot of mold problems with mine. Because they have to be strong enough to handle the coldest winter days, which makes them way overpowered when running air-conditioning in the summer, which means that when you run them in energy efficient mode, they are actively cooling only a small fraction of the time and all of the condensed water just sits there growing mold all day long. It also leaves the home far more humid than usual because it's not removing nearly as much humidity from the air as a less powerful unit running constantly would.
This isn't a problem with regular air-conditioning that is provisioned correctly for the size of your home, because it winds up actively running a lot of the time so the water is draining as new humidity condenses.
>In DACH, there's not really an alternative for many homes.
And yet in Austria, most apartment buildings in big cities are still heated by burning heating oil, gas or even firewood. Worst of the worst for air quality.
Walk through Graz in sub-zero winters and it's like you're breathing in a barbeque bonfire. Even your clothes smell like soot when you get home if you've been out too long. Which is bizarre to me, considering how much posturing and chest thumping Austria is doing about how green and anti-Nuclear they are yet they love burring wood and oil. Male this make sense please.
Sure, rich people in the bacon belt living in single family homes in the suburbs or rural areas, have heat pumps, solar panels on the roof and a Tesla in the garage, but that's a different story compared to those living in the city stuck in the fossil fuel stone age, where they have no choice over their rented building's heating method.
How do you convert the city's apartment buildings to heat pumps? Is it a technological limitation? Money limitation? Bureaucratic and political limitation? All of the above?
Firewood and heating oil isn't cheaper, it merely has lower upfront cost in exchange for a higher total cost. An efficient governance system (whether that's capitalism and banks with loans or renting out the hearpumps or a centrally planned replacement program or anything else) would figure out the financing and save the system money by updating.
Technology can make the incentives even larger. Excess money can make it easier for the governance system to reach the solution. But it's at the point where without any improvement to either an ideal system would figure out how to make the switch happen.
There is also a minor incentive problem here, mainly that a landlord can/will often offload the running costs, Nebenkosten, to the renters indefinitely.
That means they are sometimes economically incentivized to choose an option with lower initial cost but a higher running cost. Governments can/do bend these incentives via taxes but it can be hard/expensive to renovate old complexes (and that part cannot directly be offloaded by the landlord).
That's not true. A heat pump produces 1.5 to kwH of heat per kwH of electricity consumed, so it's already much more efficient than a diesel generator.
Even in winter, electricity from the grid is greener than burning diesel. I didn't find specific numbers for winter, but wind is about 30% of Germany's (just picking the biggest country out of DACH to support the point, not trying to come up with exact numbers) electricity production year-round, and wind doesn't tank in winter like solar does.
So, in short. Installing a heat pump and just taking electricity from the grid is still better for the environment. Of course, having your own solar is great if you live in a house, but you don't need it.
I'm sure you already made up your mind about heat pumps and that I can't convince you otherwise. But for other readers, let me add some thoughts to your points.
1) well, there's a grid. So as long as someone somewhere on your continent produces green energy it is viable and green.
2) arguable. Depends on your legislation.
3) Again, there's a grid. And even considering the worst case of no renewable sources at all: A heat pump (which uses 1kWh of electricity to provide 3-6kWh of heat) powered by a diesel generator is still more efficient than burning the diesel directly. Now add efficient combined cycle power plants, wind, biomass, hydro and battery storage systems...
> [it] become[s] cheaper than gas heating within 11 to 14 years
This a no-brainer for buildings with high energy use. But we looked into getting a heat pump last year but it doesn't pan out because our house (15 years old) has a very low energy use and we would not recover the costs (about 20K euros after subsidies) for 20+ years.
Yes. It also depends on the age of your gas heating as in Germany you get 20% subsidies when your system is 20 years or older, unfortunately this subsidy decreases 3 percentage points every year so when we are due it will be about 5%.
“ A total of around 575,000 residential heat pump units were sold across 11 European countries from January to March 2026, up from 494,000 in the same period in 2025”
Not a big increase on a relatively small base. What is the takeaway here?
2.3 million a year for something with a 20-30 year lifetime is a lot. It's not quite enough for "in 20 year everyone will have one", but you only need another 5 or 10 years of similar 15% growth to get there.
As a PSA, mini splits are pretty easy to self-install, and it can save you a bundle, even when buying all the equipment new. Lots of youtube videos on how to do it, though I'd add that most of them show using a manifold with analog gauges to do a vacuum test. You should really get a digital micron gauge and pull a deep vacuum.
Good point, though you generally don’t really have to handle coolant for mini splits, they come precharged. You mainly have to add more if you have a longer lineset.
I’ve heard the online EPA course/test for coolant cert is pretty easy, though.
The main thing is just making sure you test the lineset well, including deep vacuum decay, and ideally a nitrogen high pressure test.
I run daily comparisons between a gas boiler and a heat pump in the UK. Given that gas is cheaper than electricity, a well-installed and well-controlled gas boiler can still be cheaper to run. Heat pump running costs can drop drastically when combined with solar and battery storage, but that requires a much greater upfront investment.
I'm no expert on UK energy pricing, but the main difference between a boiler and heat pump is that heatpump can be, eg "500% efficient" - a COP of 5. So even if a KWH of energy is 2x the price for electricity a heatpump often comes out ahead.
Electricity in the UK is often 3x or more expensive than electricity for the same energy content. We have some of the most expensive electricity in the world.
COP of 5 when running in perfect conditions (load, EWT temps, variable stage compressor, infinite heat sink/source). You might want to research how realistic constant COP of 5 really is.
Yeah a COP of 5 is very good. 3 is much more typical.
And OP is right. When I've looked into it you aren't going to save any money going to a heat pump; in fact it will likely increase costs slightly.
So it really only makes sense to do when you need a new boiler. If you don't, it makes way more sense to get solar because that's also good for the environment but actually saves you money.
Seems like a decent place to point out that there are good savings to be had on heat pump running costs with a smart controller designed for heat pumps which can learn the dynamics of your building then preheat when tariffs are low or outdoor conditions are favourable.
I work for homely energy which has such an offering, but fwiw I genuinely think it's a good product. It's been studied by Salford uni in their energy house lab, so if anyone's interested maybe dig into that for a more neutral verdict.
I think there's one big issue for massive electrification and insulation of buildings: renting.
As a renter, I have no incentives to invest thousands in my home's betterment because I will have lost those when I am gone. As an owner, I have no incentives to make my apartment/house better because I don't live in it and I don't pay the energy bills.
Something has to be done about that if we want to combat climate change. I know in France it is now forbidden to rent again or sale when the renter leaves if the home's energy grade is F or G (A is best) but it is probably loosely enforced/easy to circumvent. And it is too damn slow ! This is for regulation but maybe there are other levers ?
As a renter I would basically have to wait for energy prices to skyrocket for it to make economic sense. I hate this situation.
Another big problem is NIMBYism and ideological opposition to air conditioners.
Installing a heat pump can require (city) permits, permission from your landlord (if renting) or HOA/condo association (if you own a flat in a shared building) which can either be or feel impossible to get.
Some cities have either actually or de facto (through requirements/regulations that are impossible or unaffordable to meet) banned air conditioners, resulting in people buying inefficient monoblock units that can't be used for heating.
Edit: Other regulatory hurdles come from rules about refrigerant handling. Refrigerant must only be handled by experts who are certified in proper handling and recovery (and who, of course, are now in high demand and charging princely prices for their work). This made a lot of sense in the times where 1 kg of refrigerant had 10 tons CO2e in global warming potential, ozone depletion potential or other dangers.
Nowadays, a skilled layperson can probably set up an air conditioner with quick-connect couplings by themselves, but they aren't legally allowed to. These cost something like 500 EUR, contain less than 1 kg of R32 with a GWP of 675, so let's say 500 kg CO2e of harm if it leaks. If you passed a law that landlords cannot prohibit installation, and any electrician that passes a quick online training can install them, you could have them all over the place very quickly.
These could then be used for covering some or all of the heating load in winter, but they'd also alleviate suffering in summer, and that's luxury, and we can't have that (especially as it uses energy to provide the "needless" luxury!)
Well, there are heatpumps made to slot into a window frame (ex: https://www.mideacomfort.us/packaged.html ). The ones I'm familiar with are made for double hung windows, which are more common in the US, though. But might be worth a look?
Do the places you are referring to not require heat? If so I don't see why having a separate heating and cooling system would be cheaper to maintain than a single system. Come to think of it I don't see why a heatpump would be more expensive to maintain than split AC. I guess there is some extra circuitry to make sure it doesn't ice up in the winter and maybe backup resistance heating builtin.
"Heat pump" can mean many things, from essentially "split A/C" (air-air heat pumps) to ground-source heat pumps, using floor heating for the output, warm water production from the heat pump, etc.
I think they mean "air exchange" (split AC) vs "heat pump" (dig into the earth to draw/eliminate heat). Not saying that's the right definition though. I am guessing at an auto-correction of what they meant.
Dug into the ground, we usually call a "ground source heat pump", or less accurately, "geothermal". The normal split systems are "air source heat pumps". AC is a heat pump without a reversing valve.
A heat pump is not necessarily dug into the earth. Rather, the flow of the heat pump is moving heat (thermal energy) from outdoors to indoors or the other way around in an air conditioner.
Depending on the direction of the coolant flow, you get either a indoor heating or cooling unit. This is best demonstrated by going in front of the outdoor unit of a heat pump, when they are cooling, the outdoor unit generates heat because it's compressing gas, which then is then expanded when it reaches the indoor unit, generating cold. Exactly like a refridgerator.
A significant proportion of the European population will only ever talk about heat pumps when they are in a social setting which allows for free conversation. And they haven't shut up about it for about 20 years now. It used to bore me to death.
imagine the President of the US and his "braintrust" accidentally making the world much more green and efficient by forcing a radical reduction in oil dependency
while they purposely end climate-change research including destroying billions in observation satellites by deorbiting them
the history written about this decade is going to be wild, if we survive it
EU severely reducing its fossil fuel imports from Russia in 2022 cut down natural gas usage by 17% and overall energy consumption by 3%. So yeah, increased price due to scarcity help a lot in shifting around the energy mix.
It's a bit shit that hits poorer people relatively more than richer people. Governments can reduce this impact by subsidizing sustainable alternatives (like heat pumps). It's still leading to inequality (unless you give more subsidy to the poor), but at least overall people will hopefully benefit.
Shame on The Netherlands: ~89% of homes still use natural gas in some way for heating [1], and their government are now "scrapping the obligation to purchase a heat pump in 2026" [2].
For anybody in TVA's electricity networks (mostly: Tennessee): they offer an annual promotion to single-family homeowners only to purchase an $1800 AO heatpump waterheater for only $250.
Maths: 85% discount on fancy new waterheater, which also dehumidifies and cools your house (passive result of heatpump).
TVA usually offers this promotion between Thanksgiving and NYE. You can order online from HomeDepot, or walk into a local store [0]. This ends up costing LESS than a new traditional resistive-type heater.
[0] either method: they DO verify SFH (by more than just ZIP code) -- duplexes and contractors not authorized/allowed
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My own $250.00 "TVA homeowner special" (as a licensed electrician):
<https://i.imgur.com/4wCez9u.jpeg> this specific design draws from both bath and bedroom [dual 6" inlets], exhausts into kitchen [single 8" outlet] | utility closet is only 5ft x 4ft (~20sqft)
Don't forget to use a pressure regulator, expansion tank (coldside, only), & (preferably) a sediment filter. Whatever you do: do NOT use a water softener before the tank.
Important caveat:
> You must swap out an old electric unit; switching from gas to electric doesn't qualify.[0]
That’s a bummer; totally would have done this otherwise
[0] https://www.hotwater.com/water-heater-rebates/tva-heat-pump-...
Interestingly, TVA/EPB/Lowes [7] never asked for our swaps (I threw all four oldtanks away).
[7] not Home Depot; AOSmith -eligible, not Rheem (can no longer edit abovepost)
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Didn't know about the gas disqualifier... or the great URL/reference (thanks)!
For future TVA homeowner installers: the website seems to indicate that you MUST use an approved contractor for the rebate — at least December 2025, in EPB/Chatt, this was not required: just had to go to Hixson Lowes and have them look up address and then paid (w/ delivery, not in-stock).
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Less than a decade ago, I helped install a 38kW [•] tankless/instaHot heater (¡¡¡ that's three 240v40a two-pole circuitbreakers !!!) into a beautiful new home. Homeowner is actively doing his part not maintaining the unit in eventual hopes of justify purchasing a new heatpump waterheater.
Godspeed.
[•] I think technically it's 28kW -rated (there's a consumer-installed limit, w/o boilermaker license), but the circuits support more w/o 80% derating applied
> I think technically it's 28kW -rated (there's a consumer-installed limit, w/o boilermaker license), but the circuits support more w/o 80% derating applied
A tankless water heater is not considered a continuous load so there’s no need to apply the 80% rule.
A 60A 2P breaker will have a trip curve that results in a thermal trip for just under 100% of rated current in around 2-3 hours. The fast acting part of the trip curve is magnetic, longer duration trips are thermal.
Here’s a link to a Square D breaker guide: https://ressupply.com/documents/square_d/QO_and_QOB_Circuit_...
The trip curve on page 25 of the pdf applies to Square D QO plug-in (residential breakers are usually plug-in, commercial are bolted on) 2-pole breakers rated 120/240V from 45A-60A. Find the 1 (times rated current) at the bottom and follow it up the chart until it intersects with the black area of the trip curve, that is approximately when the breaker will trip at 100% of its rated ampacity. Look at the left hand side to see the time in seconds that it will trip in.
It’s hard to see exactly where it intersects, but it’s somewhere between 7000-10000 seconds, or 2-3 hours.
So, you need to apply the 80% rule to continuous loads because breaker trip curves are adjusted so the thermal overload trips in 3 or fewer hours at 100% of rated ampacity. If you look at .8 times rated load, the line never intersects the trip curve.
Here’s a manual for an A.O. Smith tankless water heater:
> https://assets.hotwater.com/damroot/Original/1000/100306523....
On page 10, the 4 element, 7kW per element unit draws 58.33A per 60A breaker, 7000/240 = 29.167A, two elements a piece for 58.33A per 60A breaker.
It’s lot cheaper to wire up a 28kW electric heater if you have 480V three-phase, it’s only 28000/480/1.732 = 33.68A, all you need is a 35A 3P breaker, three #10s and a #10 ground.
240V single phase needs two 60A 2P breakers, four #6s and two #10 grounds, or if it was a single-point connection, one 125A 2P breaker, two #1/0s and a #6 ground.
The 28kW limit is from the Boilermakers Union, not ours [IBEW] =P
As much as I hate AFCI breakers, I do love a well-designed "stupid" heat-response timeout that's in compliance with the NEC. You're correct that residential waterheaters are not "continuous loads" – had slipped my mind.
I used a tankless/instahot heater (and helped install a few hundred in the early 2010s) and am so much happier with my hybrid/heatpump tank-type (it is so much cheaper to operate, requiring a relatively minimal upkeep of: an annual drainage).
Plus: there are no "miminum flow" requirements/bullshit, which results in some tempermental dishwashing among the water-conscientious (sp?).
> The 28kW limit is from the Boilermakers Union, not ours [IBEW] =P
Ahh gotcha, they must’ve pushed for some good ol trade protectionism after electric boilers came out and high-power tankless water heaters are within their wheelhouse or something like that. I wouldn’t consider it a pressure vessel but I don’t blame them for scooping up the work, lol. I’m not in the union myself, but I do manage IBEW electricians and know enough to be dangerous ;)
> As much as I hate AFCI breakers, I do love a well-designed "stupid" heat-response timeout that's in compliance with the NEC. You're correct that residential waterheaters are not "continuous loads" – had slipped my mind.
I believe electric tank style water heaters under a certain size are considered continuous loads, but tankless are not.
> I used a tankless/instahot heater (and helped install a few hundred in the early 2010s) and am so much happier with my hybrid/heatpump tank-type (it is so much cheaper to operate, requiring a relatively minimal upkeep of: an annual drainage). Plus: there are no "miminum flow" requirements/bullshit, which results in some tempermental dishwashing among the water-conscientious (sp?).
Heat pump water heaters seem amazing, 25% of the power usage of a resistive heater, and especially for $250!
I wasn’t aware of minimum flow requirements for tankless heaters, I suppose it’s necessary to prevent overheating/steam or something? I mostly see tankless water heaters as part of emergency eyewash station installations, most commercial buildings around here either use boiler water for domestic hot water heating or have point-of-use tank water heaters near sinks/bathrooms.
I have a heat pump hot water heater, and it's been awesome. It's ROI has definitely improved with all the energy price spikes. It's located in my garage (I live in Florida) so there's no shortage of hot air for it to use.
>>Florida>> "no shortage of hot air"
hot HUMID air – which heatpumps love!
Draw your inlet from [at least one] humid bathroom source, if you can. Always use insulated ducting to lessen local condensation.
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I always smile knowing that using hot water doesn't cost any more than cold, at least when the AC would otherwise be cooling (offset).
Same — I maintain four (one RHEEM and three AO's).
The AO is a much cleaner/simpler/nicer install. The Rheem stupidly requires duct adapters (for small-space, <700sqft "closet" installations). AO won't last as long, but at $250 who cares?!
>at $250
after subsidy
>who cares?!
fellow taxpayers, fellow ratepayers, people who care about the planet, etc. etc.
>fellow ratepayers
This reduces electric infrastructure demand, which is why it's subsidized. Presumably, this saves money (duh) for the company (duh) and possibly the customers (presumable duh). Presumably people who care about the planet understand this.
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Running a single heatpump waterheater is the equivalent of not driving your car, annually, according to TVA (in carbon footprint).
I'm running four [two households, ten people]. What's your question?
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edit/tone (educatable moments): <https://www.hotwater.com/water-heater-rebates/tva-heat-pump-...>
> Running a single heatpump waterheater is the equivalent of not driving your car, annually, according to TVA (in carbon footprint).
This seems a lot but for utilities which still have coal plants it seems accurate if the reduced demand allows them to close the coal plant down.
A typical car emits 4.6 tonnes CO2 per year. https://www.epa.gov/greenvehicles/greenhouse-gas-emissions-t...
Heat pump saves around 3,760 kWh per year. https://www.energystar.gov/products/heat_pump_water_heaters/...
Coal emits 1.02 tonne CO2/MWh = 3.8 tonnes CO2 per year savings from the heat pump. Natural gas emits 0.44 tonne CO2/MWh = 1.65 tonne CO2. https://www.eia.gov/todayinenergy/detail.php?id=48296
That's a pretty substantial saving which will kick in when the next administration reverses Trump's absurd orders to keep existing coal plants open.
> Whatever you do: do NOT use a water softener before the tank.
I'm curious why not? I can't immediately think of a reason why that would be bad, but I admittedly know hardly anything about plumbing.
Corrosion will destroy the tank's fittings/liner. Quickly.
So quickly, in fact, that it is mentioned multiple times in the installation manual to not do lots of things (no salt-fed softeners in bold/red/all-the-things).
Curious about this because I thought the entire point of a water softener was to prevent damage to appliances due to mineral buildup. I’ve never heard before that the salt is bad for any appliance.
Possibly obvious point, water softeners add salt to the water.
Not all water softeners add salt to the water. nuvoh2o sells a water softener that does not use salt.
While this may be true (have no knowledge | how does it work w/o salts?), the OEM will immediately void your warranty if you use any sort of homeowner water softener, per both Rheem and AOS installation manuals.
I have both; mine are warranted "platinum|10yrs" — why chance it?
Correct. This is the reason.
> which also dehumidifies and cools your house (passive result of heatpump).
Wait do you install these indoors? I get it's pretty hot in Tennessee, but still got some winters? Also isn't noise an issue?
In most of Australia these are installed outdoors. Pool heaters is another one where one could harvest indoor heat.
>Wait do you install these indoors?
Absolutely. Not just because of the heat, but because large parts of Tennessee are subtropical rainforest (~60+" annual rainfall) so dehumidification is absolutely essential. Why not get free dehumidification from heating water?
Installing an air-exchanging heatpump OUTSIDE?!? is absolutely a massive waste of energy in such a climate (and many more).
>isn't noise an issue?
All four of mine are installed in 20sqft utility closets, using insulated ducting to top-wall registers (also, insulated). For my first install, only, I used a solid metal 90° to pierce the wall/inlet (this one is loudest, basically as if the wall weren't there).
Granted, there is definitely a "louder" side (the inlet-sides), but not by much. None of my utility closets are insulated (from surrounding draw rooms), and the entire unit isn't loud enough to justify more than just a layer of sheetrock on both side of the wall/partition.
If this was installed in a garage, it would definitely be known-to-be-on, but not aggressively-so (if you have a workbench outside, e.g.). I don't know the decibel rating, but it's about the same loudness as a stand-alone dehumidifier (same wattage/concept, actually), without walls.
Should you desire the quietest install, insulate the wall (between studs) and use dual 6" insulated ducting, with switchbacks, for both inlet and outlet (that's a lot of hardware). In such an unnecessary installation, it would be whisper-quiet.
A heat pump could win as the best HVAC technology, though a better drilling for ground-sourced ones. Just a shallow drilling (up to 100m) that works in retrofit mode, such as drilling from the basement, would be a great upgrade:
- No outdoor unit that looks awful in many settings
- works well, even in the coldest winter, without a spike in electricity usage, COP 5
- very reliable with long durability
- super quiet, no ambient noise
- 20% more efficient
Currently, drilling is very disruptive in retrofits, but there is progress in compact techniques that might change the equation.
Disclaimer: angel investor in https://www.flexdrill.at/
It's usually so much more expensive than an air source heat pump that makes it completely not worth it.
Yeah, not worth it in most cases, but when things line up, it is the best.
I've built 3 houses and got a bid on ground source heat for each one. I finally pulled the trigger on the 3rd house because we:
1) Moved where it was quite a bit colder, -20F for a week is common. 2) We have enough land to trench only 6'/2m deep to bury the loops instead of drilling like we would have needed to do on the first 2 houses. 3) There was a tax credit on it 4) No equipment exposed outside
Absolutely love it and it will make it difficult to move away when we want to down size b/c we'll pay more in utilities for half the space.
We also have some air-source on an addition I built, I'd use it anywhere that was slightly warmer than where I'm at.
That depends on climate. The longer and colder your winters are, the more you benefit from the reliable efficiency of a ground source. Ground source heat pumps have been the most common choice for heating new single-family homes in Finland for the last ~20 years.
Installation is probably relatively cheaper there due to volume too. In areas where it is less common, there is less competition and fewer options for competent installers.
There is barely any people living in those latitudes. In Lithuania last 10 years air to water pumps completely took over.
Now you also need consent to drill making it much too difficult.
Yeah, recently saw some numbers for air-to-air vs air-to-groundwater, and it break even after more than 25 years, with more than twice the initial cost
What were the figures and where are you?
Bingo. Literally abandonded in Lithuania, air to air is so much cheaper. Some builders even ditch hp altogheter - basic electric underfloor heating + solar panels is so much cheaper.
I'm in New Zealand and my bedroom heater is $20 electric + $20 smart plug + $10 temperature sensor. Winter bill is ~$100 NZD. It would take ~20 years for heat pump to recover install cost alone.
Drilling alone is €10.000. The whole installation of a air/water heat pump is €10.000. Mostly not worth it.
To jakozaur’s point, there’s plenty of reasons drilling can get cheaper and there’s at least one other company working on it [1]—would love to hear about others! I’m a minimally informed amateur but my intuition is that the way it’s typically done (multiple inch borehole, U-tube geometry) is fairly suboptimal since the diameter is a lot wider than you need it to be just for hydrodynamic resistance and you get losses from the outgoing liquid cooling the incoming liquid. Dropping the diameter should make drilling a lot easier—-you can sink a 5/8”x12’ ground rod with hand tools in the right soil! (you’d still have to figure out how to make the holes meet up but I imagine there are ways of doing this).
[1] https://www.borobotics.ch/
The fact that you need to roll out a drilling rig plus crew at all is going to be a large part of that cost. For it to become interesting for the average homeowner the price is probably going to have to drop by something like 75% - but that basically kills any margins for clever new innovations...
In some potential future, there is an engineered a plant/fungus in a pot that you place onto the worksite. Months later, with regular sugar-water and hormones, it gives you a root-pipe for pennies a day.
Of course at that point we might not need the cheap pipe in the first place.
What I was trying to get at with the ground rod example is it’s entirely possible that you wouldn’t have to roll out a drilling rig and crew. To zoom about a bit, the main risk for heat pumps is really ugly winter peaks but besides that, ASHPs are perfect 90+% of the time. So the main role I see for GSHPs is backing up ASHPs to shave that peak, and once you scale back their role like that it seems like there’s a lot of ways to cut installation costs significantly.
We have a ground-source heat pump for our ADU. We did it because we were curious about just how efficient we could make the house, but I don't expect that it will ever break even financially vs a modern air-source system with resistive backup in our climate (northern New England, typically very few –20˚ nights, –10˚-0˚ more common with daytime highs in the single digits).
It works great, but it's hard to see a way to it making sense for most folks here.
You might still get the most out of it when the AMOC collapses.
Friends in south Sweden and they got a hole drilled in the front yard like it’s the most normal thing. Is it there?
The challenge is for people who live in apartment buildings in urban environment where you have no front yard you can drill into at your leisure.
The solution is of course to get a communal system. As a bonus, drilling one giant loop is significantly cheaper than drilling hundreds of smaller ones.
>The solution is of course to get a communal system.
If it's that simple why is Austria not doing this in the cities? I don't know any voter who opposes cleaner air and cheaper heating.
If you have district heating I think there might be conflict of interest / regulatory capture.
It doesn't work this way. Dense cities just don't have enough space for geothermal heating. It really works for single-family homes only, or maybe just a slightly more dense areas.
Not to mention that city infrastructure is WAY too expensive to build, anywhere. You'll spend more money on planning than on doing the actual construction.
Ground source heat pump owner here in the US. The original system was installed in 2007, and the loop field was designed to "best knowledge at the time". Well in the 20 years since then, NREL changed guidance on how far apart and how deep loops need to be installed. Rightly so, because our circa-2007 is "short looped", it's not sufficient for the house loads, but there is nothing we do about it other than putting on more expensive pumps, more expensive antifreeze and live with heat pump compressors dying pre-maturely because they are working at their design limits. All this makes it as expensive as traditional system (and if we tried to go net-zero with solar, the amount of solar required (because it runs so inefficiently) is larger than our roof area.
So I'm looking at a backup gas boiler to take load of the heatpump/ground loop (house has radiant heat).
And they are not quiet. 5-Ton water to water compressors are not quiet.
And the control system (HDX) and amount of expertise required to keep the thing running is a major barrier to getting low cost maintenance.
Maybe a 2026-designed system will work better and actually live up to the hype you talk about, but there are decades of poorly designed and discarded ground loop heat pumps that have "poisoned the well" if you will.
Does the ground source heat up (or cool down) over time, making it less effective? The deep ground is very well insulated, which is why after a century of operation the London Underground is 10 degrees warmer. I wonder whether GSHP users need to balance their load by (say) consuming more heating than they actually need in winter so that summer cooling remains effective.
I think there are two types of this, only have experience with 1 so far. Within a single season, absolutely. In deep winter entering water temp (EWT) is around 30degF (this is a pretty accurate measure of bulk ground temp). Typical for where I live is 50degF.
Other type is permanent change that persists year over year. Haven't lived here long enough to measure this. But if you pull more heat from the ground in the winter than you put back into it into summer (we use a water to air compressor for AC in summer), then yes, it can happen and does happen. Don't know if we are in this bucket yet.
Out of curiosity, has the demand stayed the same? I'm asking because you see the same with electricity grids, designed in a different time with much lower demand.
Sorry to hear this, it seems like a great system to me but you have to have the capacity right. I'm planning on getting one in the next year but the drilling will be more than we need and we opt for no glycol (yet) as that also gives us headroom
I don't think system ever met demand when commissioned (we are 3rd owners). 1st owner largely neglected the system (which I interpret as reaction to it not working well), 2nd owner had local company known for "fixing geothermal" do a lot of retrofits (new higher flow pumps, increasing diameter on plumbing within the utility room to decrease "lift/work" required of the compressors, more feedback sensors / logic boards, added backup electric water tank heating for the radiant system, switch to methanol). These fixes have seamed to limit failure modes to a smaller set of things: mainly compressors dying early.
Currently system is running 20% methanol to combat the 29degF EWT (entering water temp) in deep winter. House is in Zone 6a.
One thing I learned in researching all of this is that use of ground source over many years can move the bulk ground temp permanently. (House also has water-to-air water furnace for AC). If heat pulled from ground in winter is not sufficiently replaced by heat added during summer, can move bulk ground temp over time. (If densely packed residential ground loops ever became a thing, I think this is a real risk.). But I am not sure if we have this issue at our place, still in first year, not enough data points.
It seems like you need to add new pipes. That isn't impossible, but it isn't cheap even compared to compressors.
Drilling in the basement seems like a pain to remove the dirt you dig up. Saving yourself a couple of feet cannot be worth the access troubles
Drilling only works if you have access to a garden where to drill. Any kind of apartment has to use the outdoor unit
If you're an individual with an apartment you don't have the choice to drill.
If you're building the apartment building you have the choice to drill for the entire building, and the number of units that benefit mean this is much more cost efficient than with single family homes.
In sensible countries each housing unit have a central heating solution, regardless of where the heat comes from.
That is you thinking whatever your area does must be best. Different does not mean better. there are pros and cons.
In DACH, there's not really an alternative for many homes. Heat pumps are by now cheaper, more efficient, more versatile and definitely greener than other means of heating.
If you get one, just make sure to get the dimensioning right. They are WAY more complex to plan, install and maintain than traditional heating.
> DACH, an acronym for Deutschland (Germany), Austria, Confoederatio Helvetica (Swiss Confederation), the three major German-speaking countries
I was not familiar with this term before, had to look it up.
A great acronym as it translates to roof (Dach in german).
>[heatpump waterheaters are] WAY more complex to plan, install
Only if you place them within <700sqft (for a typical indoor residential location). Only in areas smaller will you need to duct them, somewhat similarly to:
<https://i.imgur.com/4wCez9u.jpeg> this specific design draws from both bath and bedroom [dual 6" inlets], exhausts into kitchen [single 8" outlet] | utility closet is only 5ft x 4ft (~20sqft)
As an added bonus it'll passively dehumidify/cool whereever it drafts to/from.
> They are WAY more complex to plan, install and maintain than traditional heating.
I'm curious what about them would be more difficult to plan, install, and maintain. Obviously there are many things to consider when retrofitting a building with a central gas furnace... but otherwise why would they be much more complicated than an air conditioning system?
I've had a lot of mold problems with mine. Because they have to be strong enough to handle the coldest winter days, which makes them way overpowered when running air-conditioning in the summer, which means that when you run them in energy efficient mode, they are actively cooling only a small fraction of the time and all of the condensed water just sits there growing mold all day long. It also leaves the home far more humid than usual because it's not removing nearly as much humidity from the air as a less powerful unit running constantly would.
This isn't a problem with regular air-conditioning that is provisioned correctly for the size of your home, because it winds up actively running a lot of the time so the water is draining as new humidity condenses.
>In DACH, there's not really an alternative for many homes.
And yet in Austria, most apartment buildings in big cities are still heated by burning heating oil, gas or even firewood. Worst of the worst for air quality.
Walk through Graz in sub-zero winters and it's like you're breathing in a barbeque bonfire. Even your clothes smell like soot when you get home if you've been out too long. Which is bizarre to me, considering how much posturing and chest thumping Austria is doing about how green and anti-Nuclear they are yet they love burring wood and oil. Male this make sense please.
Sure, rich people in the bacon belt living in single family homes in the suburbs or rural areas, have heat pumps, solar panels on the roof and a Tesla in the garage, but that's a different story compared to those living in the city stuck in the fossil fuel stone age, where they have no choice over their rented building's heating method.
How do you convert the city's apartment buildings to heat pumps? Is it a technological limitation? Money limitation? Bureaucratic and political limitation? All of the above?
It's incentives. Landlord pays for the installation and decides, tenant for the operation/heating.
Best way to get around this is making heat pumps more accessible (easy to get, financing options), as well as legislation (banning gas/oil heating).
Beurocratic and political limitation.
Firewood and heating oil isn't cheaper, it merely has lower upfront cost in exchange for a higher total cost. An efficient governance system (whether that's capitalism and banks with loans or renting out the hearpumps or a centrally planned replacement program or anything else) would figure out the financing and save the system money by updating.
Technology can make the incentives even larger. Excess money can make it easier for the governance system to reach the solution. But it's at the point where without any improvement to either an ideal system would figure out how to make the switch happen.
There is also a minor incentive problem here, mainly that a landlord can/will often offload the running costs, Nebenkosten, to the renters indefinitely.
That means they are sometimes economically incentivized to choose an option with lower initial cost but a higher running cost. Governments can/do bend these incentives via taxes but it can be hard/expensive to renovate old complexes (and that part cannot directly be offloaded by the landlord).
1) To make it really green and viable -> you „need” solar installation
2) To have solar installation you have to abaid to painfully stupid legistlation
3) In winter pump is as green as the diesel generator that produces energy for it to run
That's not true. A heat pump produces 1.5 to kwH of heat per kwH of electricity consumed, so it's already much more efficient than a diesel generator.
Even in winter, electricity from the grid is greener than burning diesel. I didn't find specific numbers for winter, but wind is about 30% of Germany's (just picking the biggest country out of DACH to support the point, not trying to come up with exact numbers) electricity production year-round, and wind doesn't tank in winter like solar does.
So, in short. Installing a heat pump and just taking electricity from the grid is still better for the environment. Of course, having your own solar is great if you live in a house, but you don't need it.
I'm sure you already made up your mind about heat pumps and that I can't convince you otherwise. But for other readers, let me add some thoughts to your points.
1) well, there's a grid. So as long as someone somewhere on your continent produces green energy it is viable and green.
2) arguable. Depends on your legislation.
3) Again, there's a grid. And even considering the worst case of no renewable sources at all: A heat pump (which uses 1kWh of electricity to provide 3-6kWh of heat) powered by a diesel generator is still more efficient than burning the diesel directly. Now add efficient combined cycle power plants, wind, biomass, hydro and battery storage systems...
Sounds like you're in a specific situation.
I wonder what it is and whether it applies to a lot of other people?
In what I assume is GP's general area coal furnaces are quite common for heating.
> [it] become[s] cheaper than gas heating within 11 to 14 years
This a no-brainer for buildings with high energy use. But we looked into getting a heat pump last year but it doesn't pan out because our house (15 years old) has a very low energy use and we would not recover the costs (about 20K euros after subsidies) for 20+ years.
Your existing system will not last forever. When you have to spend money anyway that changes things.
Yes. It also depends on the age of your gas heating as in Germany you get 20% subsidies when your system is 20 years or older, unfortunately this subsidy decreases 3 percentage points every year so when we are due it will be about 5%.
With any luck, oil prices will rise enough to make that conversion worthwhile!
“ A total of around 575,000 residential heat pump units were sold across 11 European countries from January to March 2026, up from 494,000 in the same period in 2025”
Not a big increase on a relatively small base. What is the takeaway here?
2.3 million a year for something with a 20-30 year lifetime is a lot. It's not quite enough for "in 20 year everyone will have one", but you only need another 5 or 10 years of similar 15% growth to get there.
As a PSA, mini splits are pretty easy to self-install, and it can save you a bundle, even when buying all the equipment new. Lots of youtube videos on how to do it, though I'd add that most of them show using a manifold with analog gauges to do a vacuum test. You should really get a digital micron gauge and pull a deep vacuum.
Also, make sure that's actually legal in your jurisdiction. It is not legal here (primarily due to handling of coolant)
Good point, though you generally don’t really have to handle coolant for mini splits, they come precharged. You mainly have to add more if you have a longer lineset.
I’ve heard the online EPA course/test for coolant cert is pretty easy, though.
The main thing is just making sure you test the lineset well, including deep vacuum decay, and ideally a nitrogen high pressure test.
Even where it's not legal you can often do much of the work and hire a licensed contractor for the "final step". It can be worth asking around.
I run daily comparisons between a gas boiler and a heat pump in the UK. Given that gas is cheaper than electricity, a well-installed and well-controlled gas boiler can still be cheaper to run. Heat pump running costs can drop drastically when combined with solar and battery storage, but that requires a much greater upfront investment.
https://x.com/AO7186252340513
https://bsky.app/profile/showpiece.bsky.social
I'm no expert on UK energy pricing, but the main difference between a boiler and heat pump is that heatpump can be, eg "500% efficient" - a COP of 5. So even if a KWH of energy is 2x the price for electricity a heatpump often comes out ahead.
Electricity in the UK is often 3x or more expensive than electricity for the same energy content. We have some of the most expensive electricity in the world.
COP of 5 when running in perfect conditions (load, EWT temps, variable stage compressor, infinite heat sink/source). You might want to research how realistic constant COP of 5 really is.
Yeah a COP of 5 is very good. 3 is much more typical.
And OP is right. When I've looked into it you aren't going to save any money going to a heat pump; in fact it will likely increase costs slightly.
So it really only makes sense to do when you need a new boiler. If you don't, it makes way more sense to get solar because that's also good for the environment but actually saves you money.
Seems like a decent place to point out that there are good savings to be had on heat pump running costs with a smart controller designed for heat pumps which can learn the dynamics of your building then preheat when tariffs are low or outdoor conditions are favourable.
I work for homely energy which has such an offering, but fwiw I genuinely think it's a good product. It's been studied by Salford uni in their energy house lab, so if anyone's interested maybe dig into that for a more neutral verdict.
I think there's one big issue for massive electrification and insulation of buildings: renting.
As a renter, I have no incentives to invest thousands in my home's betterment because I will have lost those when I am gone. As an owner, I have no incentives to make my apartment/house better because I don't live in it and I don't pay the energy bills.
Something has to be done about that if we want to combat climate change. I know in France it is now forbidden to rent again or sale when the renter leaves if the home's energy grade is F or G (A is best) but it is probably loosely enforced/easy to circumvent. And it is too damn slow ! This is for regulation but maybe there are other levers ?
As a renter I would basically have to wait for energy prices to skyrocket for it to make economic sense. I hate this situation.
Another big problem is NIMBYism and ideological opposition to air conditioners.
Installing a heat pump can require (city) permits, permission from your landlord (if renting) or HOA/condo association (if you own a flat in a shared building) which can either be or feel impossible to get.
Some cities have either actually or de facto (through requirements/regulations that are impossible or unaffordable to meet) banned air conditioners, resulting in people buying inefficient monoblock units that can't be used for heating.
Edit: Other regulatory hurdles come from rules about refrigerant handling. Refrigerant must only be handled by experts who are certified in proper handling and recovery (and who, of course, are now in high demand and charging princely prices for their work). This made a lot of sense in the times where 1 kg of refrigerant had 10 tons CO2e in global warming potential, ozone depletion potential or other dangers.
Nowadays, a skilled layperson can probably set up an air conditioner with quick-connect couplings by themselves, but they aren't legally allowed to. These cost something like 500 EUR, contain less than 1 kg of R32 with a GWP of 675, so let's say 500 kg CO2e of harm if it leaks. If you passed a law that landlords cannot prohibit installation, and any electrician that passes a quick online training can install them, you could have them all over the place very quickly.
These could then be used for covering some or all of the heating load in winter, but they'd also alleviate suffering in summer, and that's luxury, and we can't have that (especially as it uses energy to provide the "needless" luxury!)
Well, there are heatpumps made to slot into a window frame (ex: https://www.mideacomfort.us/packaged.html ). The ones I'm familiar with are made for double hung windows, which are more common in the US, though. But might be worth a look?
That's a neat proxy measurement to track.
I am probably simply confused but what’s the proxy measurement?
I assume a product related directly to another product. So when energy prices start to go up, invest in heat pump companies.
Thats what I was guessing but was thrown off because it is a pretty natural nth order effect. Gas prices go up, more efficient cars get sold.
Heat pump sales for energy costs.
More efficient hvac tech is a partial substitute for fuel.
in the south, a lot of people opt for split Airconditioning instead of heatpumps. Cheaper and much easier to install/maintain
Do the places you are referring to not require heat? If so I don't see why having a separate heating and cooling system would be cheaper to maintain than a single system. Come to think of it I don't see why a heatpump would be more expensive to maintain than split AC. I guess there is some extra circuitry to make sure it doesn't ice up in the winter and maybe backup resistance heating builtin.
Most split A/Cs can also heat.
"Heat pump" can mean many things, from essentially "split A/C" (air-air heat pumps) to ground-source heat pumps, using floor heating for the output, warm water production from the heat pump, etc.
That's the same thing, no?
It needs some extra valves to switch the flow of coolant around, but yes.
Some refrigerants are more suited for cold climates, some of which require very high pressures.
In the same way that an electric motor and a generator are the same thing.
In an EV they literally are.
I think they mean "air exchange" (split AC) vs "heat pump" (dig into the earth to draw/eliminate heat). Not saying that's the right definition though. I am guessing at an auto-correction of what they meant.
Dug into the ground, we usually call a "ground source heat pump", or less accurately, "geothermal". The normal split systems are "air source heat pumps". AC is a heat pump without a reversing valve.
A heat pump is not necessarily dug into the earth. Rather, the flow of the heat pump is moving heat (thermal energy) from outdoors to indoors or the other way around in an air conditioner.
Depending on the direction of the coolant flow, you get either a indoor heating or cooling unit. This is best demonstrated by going in front of the outdoor unit of a heat pump, when they are cooling, the outdoor unit generates heat because it's compressing gas, which then is then expanded when it reaches the indoor unit, generating cold. Exactly like a refridgerator.
Why would it be easier to install/maintain? It's basically the same machine.
Split units are heat pumps right? They heat and cool. What’s the catch? They don’t have a very high range of operation?
They’re pretty efficient
A significant proportion of the European population will only ever talk about heat pumps when they are in a social setting which allows for free conversation. And they haven't shut up about it for about 20 years now. It used to bore me to death.
imagine the President of the US and his "braintrust" accidentally making the world much more green and efficient by forcing a radical reduction in oil dependency
while they purposely end climate-change research including destroying billions in observation satellites by deorbiting them
the history written about this decade is going to be wild, if we survive it
EU severely reducing its fossil fuel imports from Russia in 2022 cut down natural gas usage by 17% and overall energy consumption by 3%. So yeah, increased price due to scarcity help a lot in shifting around the energy mix.
It's a bit shit that hits poorer people relatively more than richer people. Governments can reduce this impact by subsidizing sustainable alternatives (like heat pumps). It's still leading to inequality (unless you give more subsidy to the poor), but at least overall people will hopefully benefit.
> overall energy consumption by 3%
Is it possible that some non-trivial part of that number comes not from increased efficiency but from losing some energy-dependent industries?
It might be difficult to separate that out from the effect of US tariffs.
Shame on The Netherlands: ~89% of homes still use natural gas in some way for heating [1], and their government are now "scrapping the obligation to purchase a heat pump in 2026" [2].
[1] https://www.cbs.nl/en-gb/news/2025/50/ever-more-gas-free-hom... [2] https://www.abnamro.nl/en/personal/specially-for/preferred-b...