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.
> 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-...
[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
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.
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?).
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.
You definitely sound just like us =P
>minimum flow [for tankless]
Yes, my brother has a kitchen pretty far from his tankless and if you don't have a disrespectful (i.e. anti-environmentalist) flow going, it's going to get cold and then stay that way for quite a while. It is aggravating, even as an occassional guest in his house – the whole damn line has to heat back up, again!.
For point sources located far away from the heater, you are supposed to install a return loop. Modern tankless have a tiny (1-3 gallon) superheated tank and recirculation pump designed specifically for this use-case.
You can pry my continuous water heaters from my cold dead hands. What is much more annoying is running out of hot water when you have a peak guest load in your house right before an evening event and everyone is taking showers at the same time after a day out.
Since I use very little hot water otherwise, it pencils out for the environment too! The few times a guest is in a far guestroom and needs to use a small point of use hot water source, the few extra gallons of use to wait for it to kick in is a rounding error.
The two tankless heaters I have installed in my place are by far the single best upgrade I did since buying the house. I often comment on how much better my quality of life is with them vs. before they were installed.
I would never use a water heater with a tank ever again unless forced to. Other than air conditioning it is basically one of the top luxuries I work to provide for myself. My wife can take a bath, 3 other guests can shower all at the same time along with two loads of laundry and a dishwasher cycle going. No worries and no waiting around for an hour for hot water to regenerate. Since it's designed for peak loads and only spins up the second unit on-demand, it's much better in terms of energy use than a boiler designed to support those types of loads it sees 2 or 3 times a year at most.
If I were re-designing my system today I might do a heat pump water heater in-line with a continuous water heater, and the continuous only fires up once the tank runs empty.
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).
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?!
after subsidy
>who cares?!
fellow taxpayers, fellow ratepayers, people who care about the planet, etc. etc.
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-...>
Short term gain, long term pain. The story of our entire electrical infrastructure the past couple generations. Why invest in capital infrastructure like generation or transmission capacity when you can simply reduce peak demand via stuff like this.
Eventually you run out of cheap tricks and need to actually build things. We are roughly at that inflection point now - brought forward maybe half a decade or so by datacenter demand.
We had it really damn good the past 30-40 years due to investments in all area of the grid our grandparents and great grandparents paid for. Then we decided it was cheaper to let a lot of that stuff age out and deteriorate vs. replacing it via efficiency gains and de-industrialization. We reap what we sow. It was obvious electrical demand was going to increase at some point, and we have run out of the cheap parlor tricks of the past couple decades while we let everything else decay around us.
It's been incredibly frustrating to watch since I was a teenager 30 years ago and figured out why electric companies would pay someone to use less power against the obvious incentives. It's so they didn't have to do their jobs - just sit on capital equipment others paid for and collect rent.
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.
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.
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).
I have both; mine are warranted "platinum|10yrs" — why chance it?
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.
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.
- 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/
Now you also need consent to drill making it much too difficult.
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.
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.
Of course at that point we might not need the cheap pipe in the first place.
It works great, but it's hard to see a way to it making sense for most folks here.
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.
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.
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.
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.
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
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 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.
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.
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.
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?
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.
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?
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).
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.
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).
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
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.
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...
I wonder what it is and whether it applies to a lot of other people?
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.
Not a big increase on a relatively small base. What is the takeaway here?
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.
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.
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.
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.
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!)
Covid was the wakeup call that globalization was dying a slow death, and the first trump that world cop America was also on the way out.
Oil dependence in a top level national security concern of the last 150 years (hey, what really triggered WW1?), yet the primary means for independence has been politically suppressed for 50 years.
How soon would we have has better PV, better batteries, better heat pumps with proper subsidies and research starting with the 70s oil shocks?
"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.
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.
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
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.
Is it possible that some non-trivial part of that number comes not from increased efficiency but from losing some energy-dependent industries?
Lean into that. You’re currently a generic sales product. Focusing on a growing space, provided it doesn’t have an existing solution, will focus your team, product and pitch to both customers and investors.
[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...
