Heat Pumps – The Well-Tempered Future of A/Cs
spectrum.ieee.org
spectrum.ieee.org
These things are quite expensive. I think the HVAC installers are making a large commission though. The actual equipment costs much less than that.
There’s a local lot with a used 2021 Ioniq with the usual “used car dealer” hand-lettered sign proclaiming the $5,750 provincial rebate. I’m also fairly certain the car had its price inflated by that much by the dealer, or will climb by that as soon as negotiations start.
(1) https://www.apexautogroup.ca/inventory/2021-hyundai-ioniq-el...
All that is to say, my first guess is that the GP was quoted a high-SEER unit for name-ish brand equipment.
Also, I have 15k BTU available for one or two additional head units. I opted for this approach instead of under-sizing the heat pump or assuming we'd need the extra head unit and buying them during initial install. Half of our basement has no ducting so we thought a unit for heat would be nice. Also considered adding another unit in second floor landing for additional capacity. Not sure yet if we will.
My only complaint is the Kumo cloud is terrible.
They’re right though, the Kumo app is truly awful. Which is sad as it’s also quite useful.
Otherwise, heat pumps are essentially the same as modern A/C units.
That said there was basically no difference in putting in an A/C only unit vs a combination. Technology wise it's the same so to speak just running in reverse in winter vs summer. We use the heat pump down to -15C-ish then I usually shut it down and just use the baseboard or if awake the stove (looks much nicer ;))
It was a no brainer to get the combination unit really. I don't get why it isn't the default nowadays and A/C and heating are thought of as separate concerns. We just don't have ducting, else we could A/C the whole house vs. just one floor.
And I can definitely attest to the heating element aka defrost. We don't have actual resistive heat in the pump as we have the baseboards anyway but the lower the outside temp goes the more it has to defrost the outside as it freezes up. As winter goes by, icicles form underneath the outside unit where the defrosted ice drains out and refreezes.
It's actually amazing that the thing can extract heat from -10C air outside to heat up air that's already 21C inside to heat it up even further!
Generally true, as the mini-splits (have) tend(ed) to operate down to lower temperatures, but the heat pumps that look like 'traditional' outdoor A/C units are getting down there as well: for example this Lennox unit can work down to -4F / -20C:
* https://tech.lennoxintl.com/c03e7o14l/viu12ch2uv/ehb_sl25xpv...
That'll provide pretty good coverage of the year in many parts of North America before something like a gas furnace needs to kick in. (Speaking as someone who lives in Canada.)
I'm well north of Chicago. The heat pump is rated to -22F but have the lockout set to 15F to cut over to the furnace. Mostly for wear and tear reasons. But it has a COP rating of 1.75 at 5F. So still more efficient than any furnace well below where I run it.
It sounds like they quoted you a bottom of the range 11 SEER A/C vs a top of the line multi-stage compressor variable speed blower 19 SEER heat pump system. Those are not the same thing.
Is this in the US? Maybe the market is distorted just because not enough people are buying them yet, so nobody has much stock and there's little competition... We have that problem I think for air to water - super common in the UK and Europe, but since everybody uses air to air, split and ducted systems are super cheap but air to water are quite expensive. I really would quite like some heated floors in my bathrooms if I end up doing a big renovation, and don't want to go electric in-floor because hydronic with a heat pump should be more efficient.
The US generally has cheaper labor, less construction rules, and cheaper components due to volume . the solar thing is mysterious to me.
One has a lower rate of "undesirable outcomes" and thus when the option's binary like that then the choice is clear.
The guy made no attempt to upsell me and if anything was pushing the cheapest option
Suffice to say I don't plan on staying at that house long enough to ever get my moneys or enjoyment out of it. Bummer.
--
I think it's true that the cost only goes up "a little" between models, but the issue is, they make you go up across the board of equipment and it all adds up dramatically. The high end option requires buying their custom thermostat which was $1200 alone
One caveat to that is if you have a furnace, they may have wanted to install a full new air handler and run electric emergency heat vs just swapping the coil and condenser.
You can configure a heat pump coil with a furnace as the emergency heat but it might take some more thinking than an off the shelf AHU condenser pairing that maybe the contractor wasn't comfortable with doing that.
It's timed to only use power right in the middle of the day when the sun is shining, and in the middle of the night when power is cheap. (needs both because the tank is fairly small and my kids like long showers)
Every one of these “heat pumps are the future” articles is so soft on data, and they often fail to explain the basics or a simple “why.” Once we get past the clickbait heat pump articles, we can actually make an impact.
A heat pump operating at 250% efficiency will use just as much natural gas as a furnace operating at 100% efficiency.
Modern heat pumps can often exceed 250% efficiency, making them use less natural gas, even if they are ultimately powered by a natural gas burning power plant.
I vaguely recall I did some back of envelope math a couple years back and determined that a natural gas powered heat pump was actually more efficient (in terms of emissions) based on my grid power source mix. Solar breaks that equation obviously.
Plus, they can run on any power source, including green and/or decarbonized.
They're quite popular in the Netherlands due to high natural gas prices (since the Ukraine war) and two types of government subsidies. One is a direct subsidy on buying a heat pump device, the other is based on our energy pricing.
Basically you can offset all energy-taxes across the year with solar production. Everything you over-produce in summer carries over to the winter. So if I assume for example that my solar system is written off in 10 years to zero (reality is probably better than that) my total energy cost per kWh is only 7 cents all year round.
A pretty low capacity heat pump is able to provide 90% of the heating and cooling of a normal house. They're combined here with gas based systems to cover for the few days a year that it's exceptionally cold or when you need more hot water than the heat pump could deliver. That means you can buy a much smaller capacity (cheaper) heat pump.
If you compare the running cost of heating at only 7 cents per kWh with a heat pump to natural gas prices "pre Ukraine" it'a already roughly about 4 to 5x cheaper. Now with gas prices nearly doubled you're looking at a 8x cost saving with a heath pump vs using natural gas. The only hurdle is that you need to buy and install a heat pump device, so it takes some time to make that back.
The government is planning to slowly reduce the energy-tax offset from 2025 to 2031. But even without that it's expected that the move from gas to heat pumps will continue.
No heat pump will help if your house is leaky or under insulated.
That said, we should do both heat pumps and insulate better.
Note that there are some misleading efficiency claims for gas plants around 60%, but those are not for thermal-to-electric efficiency but for generating electricity plus district heating from waste heat.
The brand new EPR achieves only 37% thermal efficiency and that is considered a good number for a power reactor:
https://www.world-nuclear.org/information-library/nuclear-fu...
https://www.ge.com/news/press-releases/ha-technology-now-ava...
Approximating natural gas as 100% methane, that means the thermal-to-electric efficiency on a higher heating value basis is more like 57-58%:
https://en.wikipedia.org/wiki/Heat_of_combustion#Heat_of_com...
Neither of these efficiency measures include district heating with waste heat.
- spray foam around windows (requires removing trim)
- caulk joints/spray foam rim joist in basement/crawl space
- spray foam around any attic can lights/duct work
- make sure ducts and air returns are sealed properly
Do a blower door test and see where the air is coming in/out:
* https://www.energy.gov/energysaver/blower-door-tests
* https://www.youtube.com/watch?v=msZ_E-4GFs8
* https://www.youtube.com/watch?v=Q5vHxgq7GKo
Then plug the holes.
Fixing unintended holes in exterior walls is probably also reasonably safe.
However, randomly plugging intended leaks without understanding how the house is supposed to breathe can lead to condensation issues (mold and rot), carbon monoxide poisoning (if you have natural gas) and radon poisoning (if that is a thing where you live).
If you want to do more than I mentioned above, consider hiring an architect, or reading up on house ventilation designs.
If possible and if you have the funds, try to do a retrofit: https://ekobuilt.com/2019/04/24/retrofitting-an-older-home-t...
https://www.buildwithrise.com/stories/passive-house-retrofit...
You don't have to do all the the things to improve performance -- you can pick and choose.
Can you say more about what your comment is supposed to mean?
I've lived in a home with a literal hole to the outside. During the winter we had to run the radiators non-stop and it was still freezing.
If you are trying to save energy, then sealing up and improving insulation will generally have the largest bang for the buck.
The gist is that we’d need to spec larger units and/or run them harder than usual, removing savings vs. gas.
My parents' house in France is one of those hundred-year-old stone ones. It's fairly cool in the summer, but it gets quite cold in the winter. My father did the insulation work himself (he's not in construction) for fairly cheap and saw his gas bill halve.
A worked example - In AU gas is metered per MJ - 3.6MJ/kWh. So 3c/MJ means that gas is equivalent to electric heat at 12c/kWh. Heat pump multiplies that by roughly 4x, so 48c/kWh is the Breakeven point for a heat pump vs gas heating.
Heat is heat, it makes no difference. insulation would save you money on all heat sources though, and can be a pretty cheap upgrade (insulating the roof space, for example).
We can assume that you currently have a high power (e.g. 28kW+) gas heater and radiators that can only emit that kind of power at high water temperatures. This system works in tandem (place where has is burnt and devices that emit the heat throughout the house). A leaky house typically needs a higher heating power in the interest of comfort: it'll have a higher power loss, and you'll want to not spend days bringing it up to room temperature in case the power was out or what not. These heating systems are usually overdimensioned, so any variability in the power loss of the house is compensated for by simply upping the power output.
A heatpump is lower power, and therefore slower, and therefore you'll want to limit the heat loss of the house, because when things go wrong (somebody left a window open in winter), you're gonna have to wait some time before the pump's caught up. Calculating a building specific optimal heat pump power is already trickier, and it's trickyness is increased without that insulation.
Which doesn't meant that you cannot do it yourself! You can simply accept that response times are going to be slower (so, if you flip the temp up from 17C to 20C that it's gonna take half a day). Best is to just set it to a temp and leave it there, it's no longer the advantage it was to modulate.
Most important is to not underdimension the heat pump. I've never seen a salesperson offer it, but there's online communities of people who can and do calculate it for older houses (gas consumption is a good proxy). One thing to understand is that heat generator power (be it a heat pump, gas heater, whatever) needs to match the heat emission power of the system that releases the heat (radiators and floor heating most likely). The water is gonna run at lower temps with a heat pump, so that means that your radiators will emit less heat, and probably not enough. You need to make sure that at the water temp the pump outputs economically the power output of the delivery system matches. This usually means putting in floor heating and/or significantly larger and more efficient radiators.
This is a pretty broad topic, and you can watch videos from this channel to learn more: https://www.youtube.com/watch?v=dReyrSGokEQ
There are options to do a full passive house retrofit, or just add exterior insulation if you have the funds and inclination. Plus you can get better air quality with filtered air, lower mold/pollen issues, lower noise if you care about that and overall home comfort.
https://www.buildwithrise.com/stories/passive-house-retrofit...
People love throwing in about how effective insulation is, completely ignoring the vast difference in difficulty and cost it actually represents.
Putting more insulation in the attic does not mean redoing the roof. Depending on what you have it might just be blowing in some insulation or adding matting. Of course there are options like spray foaming but it's not the only one.
You are of course right that if your walls are completely uninsulated you will probably want to rip out that dry wall and that will cost you. Maybe blown insulation is an option too depending on your specifics.
Do some math and see if it makes sense to do it if you don't want to do it purely for the sake of the planet. Drywalling isn't that big of a deal actually. The worst would be the ceiling and you don't have to touch that. Regular drywall on a wall is easily done solo by a home owner. Been there, done that.
It's funny what money makes you do. I had a choice to pay tens of thousands to have professionals do it or pay hundreds for materials and do it myself. I did lots of TIL and I have beautiful white walls again.
Depending on the house, location and condition, adding exterior or interior insulation and/or aero barrier, or spray foam could be more cost effective and not so invasive as you think.
https://www.youtube.com/watch?v=_nOI99ew5MM https://www.youtube.com/watch?v=eYjF1afRqvE
So.. they work in two directions.
The market for evaporative water coolers is niche, or probably only big in the developing world. Other than that water coolers use refrigeration aka a heat pump.
Ive only ever seen water coolers in the US, mainly in the South, and they're loud
https://www.iea.org/reports/the-future-of-heat-pumps/how-a-h...
or a simpler article https://en.wikipedia.org/wiki/Heat_pump
It is different from a radiator or a furnace.
I am not trying to change existing terminology, I am using existing terminology. Air conditioners (A/C) are devices sold to only cool a house:
* https://www.lennox.com/products/heating-cooling/air-conditio...
* https://www.carrier.com/residential/en/us/products/air-condi...
* https://www.trane.com/residential/en/products/air-conditione...
Heat pumps are devices sold to both cool and heat a house:
* https://www.lennox.com/products/heating-cooling/heat-pumps
* https://www.carrier.com/residential/en/us/products/heat-pump...
* https://www.trane.com/residential/en/products/heat-pumps/
* https://www.ehpa.org/about-heat-pumps/
See also US Department of Energy:
* https://www.energy.gov/energysaver/heat-pump-systems
And most definitively of all, Alec of Technology Connections:
Any expert care to explain it in layman's terms?
* Heat pumps, when referring to HVAC technology specifically, refer to systems that are essentially the same as A/C units, except they're designed to work in reverse.
* The term "heat pump" when used in Europe, more-often refers to geothermal heat-pumps ( https://en.wikipedia.org/wiki/Ground_source_heat_pump ) which is very different to an A/C-style heat-pump, though achieves similar end-result (livable indoor room air temperature).
As someone who spends a lot of time in the year in both North America and Europe I frequently come across people confusing the two.
There's a process called a "vapor compression cycle" which essentially works by moving energy from a cold area to a hot area (which makes the cold area colder and the hot area hotter).
Air conditioning is when you put the cold side of a vapor compression cycle in a building to keep it cool.
The term "heat pump" most typically refers to a device where the hot side of the vapor compression cycle is put in a building to keep it warm.
However, many heat pumps have an air conditioning mode, where the hot and cold sides of the vapor compression cycle switch places depending on the season. So air conditioner refers only to cooling, while heat pump may refer to heating along or a device which can both heat and cool.
An air conditioner uses a compressor to convert a refrigerant and sends the compressed fluid through a condenser. The condenser rejects heat from the system into the environment. This is the component of an air conditioner that is found outside. The compressed fluid is then passed through an expansion valve and into an evaporator where it is allowed to expand. Expansion is a process that requires heat. The heat flows into the expanding fluid from the environment inside the home. Air is blown across the evaporator coils to transfer heat energy from the home into the fluid which is then returned outside.
A heat pump is capable of reversing the flow of heat energy. The flow of fluid is reversed from an air-conditioner using something called a reversing valve. The compressor sends compressed fluid into the home where heat is rejected through the evaporator coil. The fluid then flows into the condenser coil and is allowed to expand outside, drawing in heat from the outside environment. The heated fluid is then returned to the compressor and the cycle continues.
In HVAC terminology an Air Conditioner is a one way physical heat pump and a heat pump is a bidirectional physical heat pump. Hopefully that helps clear it up a bit.
If you are able to run this system backwards, you could in theory swap which side is a heat sink (the cold side) and heat source (the hot side). While a traditional A/C cannot do this, heat pumps can electronically switch which side of the system is collecting the heat and which side is releasing it.
This is an improvement over resistive heating (think space heater) because we’re not pumping electricity into some filament that resists current flow and emits off heat due to the resistance. Instead, we are taking heat from inside and moving it out or taking heat from outside and moving it in.
Fun fact, a resistive heating device is a rare case of something being 100% electrically efficient in that all the energy it uses will be turned into heat, whereas heat normally is a byproduct of imperfect conductors, which everything is, and is therefore considered wasted energy in almost all other applications.
My understanding is that you get considerably more heating per watt-hour with a heat pump than with resistive heating, though. I get that it's not creating that heat but moving it, but still that seems like even more efficiency from the perspective of energy consumption per useful heat made available.
OP said electrical efficient so the goal is conversion of electricity to heat and it’s 100% efficient.
Even an electric heater compared to a propane heater is more electrically and energy efficient, but it’s not as storage-efficient (because fossil fuel gases have much higher energy density per volume AND weight than lithium batteries).
A heat pump is more electric bill-efficient.
I am not an engineer and I am only nitpicking to have fun, so don't engage me if it's not fun, but doesn't some of the energy go into degradation of the materials used to build the device?
I said 100% electrical efficiency because from the prongs of the plug, through the conductors in the appliance cord, the rheostat, all electrical connection and contact points, and of course the hearing element itself all will product heat as a consequence of electricity flowing through, and being resisted by, it’s various components.
It was pointed out that this does not mean “energy bill efficient” which is totally correct: this whole thing is a somewhat silly thought experiment to consider what it really means for something to be efficient.
The closest analogy that I know of is in electrochemical processes where some of the energy input is allowed to take different forms. If you put in 85 units of electrical energy, 15 units of waste heat from a different process, and get 90 units worth of product, your process is 90% thermodynamically efficient, but has better than 100% electrical efficiency. In the case of a heat pump, measuring units of heat per Watt-hour is a bit like this in that some of the input energy (for the heat generation) has already been provided by a different process.
Heat pumps in particular are getting a push from "green" initiatives because they only use electricity for fuel which can potentially be supplied by "renewable" sources.
ie; it's a buzz word.
It may not be as green as pure electric can be in theory, but in large portions of this country electric isn't all that green either.
Heat pumps appear expensive to operate. Imagine running your AC year-round... that very thought makes many-a-homeowner shudder.
It's a niche, I give you that, and the plate can only be used with specific sized woks, but they exist.
I've seen induction cooktops in commercial kitchens before, maybe they were just being stupid?
They also can operate at >100% efficiency. Under the right conditions (I'll let someone who knows more about it fill that in) they can provide more heat than the same amount of power going into a resistive heater (which is I think per-se 100% efficient right?). Kinda wild.
But yes, mechanical might be up to 600% efficient depending on how you think about it as moving heat around based on energy usage per therm delivered inside the home is really what people are looking for.
That's lab figures though so I guess similar to car efficiency figures.
Trying to parse the mumbo jumbo, I think these articles are trying to point out and encourage the trend of designing new installations of cooling systems around cooling and heating, with a reversing valve and whatnot. Because it no longer makes sense to lean on a separate heating system that burns fossil fuels. But gosh I wish they would just come out and say this directly instead of beating around the bush as if "heat pumps" are some magical new invention.
My parent’s house had a heat pump then and does so today (albeit much improved over the decades).
> Heat pumps are also compatible with natural refrigerants with lower climate impacts. They can consume less electricity than conventional central air conditioners
Like no, any efficiency gains for cooling have nothing to do with a unit being a "heat pump". And same thing with refrigerants - adding a heating mode can only constraint the choice of refrigerants. So they're touting benefits that have nothing to do with "heat pump" and everything to do with newer technology - but instead of describing this accurately, it's just being ignorantly lumped under this "heat pump" banner.
That’s what happens when few people are willing to pay for quality research and writing.
All that said, it is relatively recently that Americans have had access to heat pumps this efficient and they work reasonably well in sun-freezing temps.
I grew up with heat pumps. It was pretty normal for it to kick into emergency (electric heat element) when the weather got nasty (for DC, so the mid-teens F).
I don't have heat pump experience, or even much central AC experience, but I do know that there has been many advancements that make them practical for a wider audience rather than the previous niche. I wish articles would describe these advancements rather than effectively saying "a heat pump is this new awesome invention, go buy one".
The article says that heat pumps are "compatible with natural refrigerants with lower climate impacts". Why couldn't A/C units use the same natural refrigerants?
Also all refrigerators contain a heat pump.
I guess I'll jump on the bandwagon, while my comment is tangential, it does have to do with the article's focus on reducing greenhouse gases and fuel consumption.
Switching to a heat pump should be done in all cases where a traditional A/C is being replaced, but the biggest bang for the buck is in how the house is constructed in the first place. "Passive solar" orientation and insulation can prevent a HUGE amount of energy consumption. To point to another HN post article:
https://thebaffler.com/salvos/construction-time-again-sisson
I've been saying for 20 years here in San Diego county, that if developers built track housing with passive solar orientation, and covered them with photovoltaic, the neighborhoods would be power plants. They could offer free HOAs and free electricity for the life of the house. Instead, we orient, organize and build for the maximum efficiency of a group of people who are only onsite for about 1 year (the developers) and then leave the people who live there for decades holding the bag.
In San Diego
Then this recent rise in popularity elsewhere dispelled that notion.
Also, I'd never want a ductless system as they look awful in a room.
They are the future though. Especially as new regulations go into effect by 2035. Sadly, many American manufactures haven't taken it seriously and are far behind the Asian companies like Daikin.
[0]: https://www.supplyhouse.com/LG-LDN127HV4-12000-BTU-Multi-F-C...
Salesperson said there is excess demand for both labor and machinery for heat pump installations in the past few months. I wondered at the time to what extent this is a regional phenomenon (seattlites are nerds who like energy efficiency) vs. supply chain issues vs. a sales technique.
Interestingly, I learned that it will be too cold for heat pumps <10 days out of the year, so most people either keep their gas furnace as backup, or install an electric furnace for these rare days.
It's also the case that demand is huge.
I was interested in doing an air-source heat pump (because hey, my furnace was 19 years old and would have to be replaced soon anyway), but due to the excessive cost, the payback time was figured to be something like 50 years. I would have loved to do that, but it just doesn't make sense. Instead, it was new AC unit + new natural gas furnace.
Nevermind ground-source, which would have been much more expensive.
I am not sure I would pay $27k for the whole install, but once it's there I've found it to be great. Extremely inexpensive to run and with all of Seattle's power being carbon-neutral, totally guilt free to set it to 68F at night during a hot summer day.
https://freshchalk.com/greenwood-heating-air-conditioning-se...
May I ask where you are located (generally)?
A decent heat pump sized for that square footage should cost well under $10k, and it's pretty unlikely your house would need so much work to install it that the labor involved could make up for the rest of that quote.
Anyway, my heat pump just stopped working this weekend, and its getting very hot in here.
I don't fully understand why this is the case, but I hope that there's something that can be done to improve it. I'd love it if I could drive my AC unit as a heater for 95% of the winter, resorting to natural gas only during in the extreme cases.
However, even in the midst of winter, gas heating bills rarely climb above $100 monthly.
What am I missing here? It seems a heatpump, while more efficient, will cost significantly more to operate. Natural Gas is cheap... and clean enough.
1) Natural Gas is vastly cheaper in most/all of the US.
2) Homes still require an alternative heating source when temperatures drop to low levels (coincidentally when people need heating the most).
So, even if a heatpump is technically more efficient in terms of emissions, the technology does not solve all of the problems it's attempting to replace. Additionally, Natural Gas is vastly more clean in terms of emissions than some other alternatives still used around the country.
There's no way the average home is going to stomach 2-4x more heating expenses on average without some real tangible benefit (hand-wavy emissions numbers don't factor into the average homeowner's decision making).
I must be missing something here...
> ... > I must be missing something here...
Yes you are, your natural gas subsidized, i.e. government handout, i.e. you're not paying the real market cost.
Second, heat pumps do not have issues with cold temps, unless you're at like -40c. They're used all over the nordic countries - including above the arctic circle.
Your energy grid is shit, which is why your electricity price is so high.
> Your energy grid is shit, which is why your electricity price is so high.
Adding a heatpump solves this issue, or makes it worse?
In Germany you get way cheaper electricity prices if you allow this.
What do you mean by "modulate"? Your utility provider decides how much heat your home gets? That's a very strange concept.
If you have warmer days now and then then you'll start saving money, and eventually it'll pay for itself. Where I live (cold winters), the cost was covered in only two years.
The only backup heat I had with the heat pump was electric resistance heat, which I needed to use only once or twice each winter for a few hours at a time.
Obviously you wouldn't install solar panels and a battery just for this, otherwise it's very much not free, and probably a lot more expensive than burning gas. But if you already have the solar+battery install, and have enough capacity, it could even be cheaper to operate than a gas furnace.
We cut the amount of gallons we used by over 50% compared to last year. Sure the oil infrastructure is needed to get it delivered (I wish we didn't need it) but I'm very happy that our heating (oil+electricity) bills are so much lower, even with the increased oil prices.
We went with a mid-range system but now I kind of wish we sprung for the "Cadillac" version.
There are tax breaks involved with installing "energy star" rated equipment. Perhaps we ought to start witholding the star from AC units that are not easy to convert to heat pumps (and from thermostats, etc, which are not ready to handle the conversion).
(Seriously, where I live, you will likely pay $1k or slightly more to drain and refill the refrigerant. The hardware for an entire modern heat pump, indoor and outdoor components, is maybe $3-4k. Is it really worth it to drain an old existing unit, cut the pipes, add a reversing valve, retrofit in the controls, pressure test everything, deal with the fact that the outdoor unit (formerly the condenser coil) will start producing copious amounts of condensate that the manufacturer and installer did not anticipate, and refill the system?)
To add to the list of why this whole idea seems dubious: a conventional air conditioner operates with its evaporator coil at a balmy 50F or so. If you reverse it, the outdoor coil will become the evaporator, and it will operate below freezing if it’s cold out (even if the outdoor temperature is a bit above freezing). As a result, condensate can form and freeze on the coil.
This is entirely manageable (any modern heat pump can operate in decently chilly conditions, and heat pumps equipped for low temperature operation can operate in very cold conditions), but I expect that at least some engineering is involved.
It cools better than the old system, and the fact that it runs longer instead of in short bursts means it regulates humidity way better too.
For heat we did go dual fuel, which means the backup heating element uses gas, since we already had the line. This works really well in a cold snap where temps drop well below freezing.
Nate the House Whisperer is a guy who has been trying to build a new generation of HVAC practice, and though he says he's usually a libertarian, he advocates for adding a tax to AC-only units that would eliminate this price difference (or some similar practice, I forget the exact details...)
There are two popular varieties:
- Ground source heat pumps. Those work pretty much anywhere; just dig below the perma frost and you are good to go on the northern tip of Canada, Alaska, Norway, or wherever. Works great, ground temperatures tend to be very stable and it actually goes up the deeper you dig.
- Air source heat pumps. The expensive ones still work okish at extreme temperatures like -25-ish degrees C. Which is a reason these are actually more popular than ground sources even in places (e.g. most of Scandinavia) that reliably get such temperatures each winter.
But its an unfortunate fact that there are places in the US where installers that recommend heat pumps can't be found for 100 miles. It doesn't really matter if I'm technically correct about the merits of the tech in principle--if I can't find somebody to fix my system and my pipes start exploding, I've still made the wrong decision.
Also, heavy snows cause power outages in places where tree limbs fall on overhead lines. If gas outages happen... well I've never experienced one. Sure, if I lived in Norway I'd have a government that cares about updated infrastructure and I wouldn't have these problems, but since I don't, I do.
Given my local constraints, a dual-fuel system sounds pretty great.
Which are all good reasons why the market for domestic solar, batteries, and heat pumps is so hot right now. The US is no exception to this.
Most houses in Finland have a (decent) fireplace for heating in case of an electric outage.
If I lose power, my gas boiler does me no good. A gas boiler will use pumps (and likely a power vent). A gas furnace will use a fan and a power vent.
[1] You can of course get a much larger heat pump to compensate, but that leaves the unit way over-sized for cooling loads.
In other words heat-energy should be going into cold side of the heat-pump (even at a low temperatures) at the same rate as it is coming out the hot-side at high temperatures. Reduce the heat in, and you will reduce the heat out.
My understanding is that improved low temperature performance has something to do with varying the amount of refrigerant in the loop: https://www.mitsubishicomfort.com/articles/keep-warm-this-wi...
Which I guess similarly explains a lot of weird conversations and people talking past each other where busses are concerned.
(I’m referring to normal air-to-refrigerant-to-air heat pumps. I know of a really weird system that is thoroughly American and an utter pain in the arse to replace because it’s specialized and undocumented. It’s quite loud, too, because it’s single-speed, and that single speed is waaaaay too high.)
Two solutions to this problem:
1) get a bigger/better heat pump.
2) improve you building insulation and figure out where you are losing energy.
We've been using 'reverse-cycle air-conditioners' for heating in Australia for decades. I'm puzzled as to why there is any debate at all on their use for heating. A heat-pump is far more efficient for obtaining heat than direct resistive heating using electricity.
Many houses here use no other form of heating at all. And then at the press of a button, we get cooling in summer too. What's not to like?
* I also have a heat-pump condensing clothes dryer. The overall heat thrown out into the room is extremely low. The hot-air comes out the hot-side of the heat-pump to dry the clothes. The warm-moist air then passes over the cold coils, condensing out the water from the clothes and returning the heat to the cold-side of the heat pump which then pushes that heat-energy out the hot-side, producing more hot air to complete the cycle. I've had this Miele heat-pump condensing dryer going strong since 2009 - 14 years.
Meanwhile, I'm annoyed that heat pumps that dump the waste heat into the hot water cylinder aren't standard.
Seems like its still pretty low in Europe outside some northern countries. Germany is less than 2000/100000 people.
https://www.theecoexperts.co.uk/heat-pumps/top-countries
Meanwhile this link says US has a 15% adoption rate across all income groups. That seems higher than I expected.
https://energypost.eu/u-s-heat-pump-adoption-is-evenly-sprea...
Is there a better source on heat pump adoption rate in Europe and US?
For applications like commercial buildings, public swimming pools, industrial sites, etc. can (and increasingly do) definitely benefit from that kind of combination though.
I think this might eventually become a thing once science gets us far enough that there's an "obvious" refrigerant choice for most applications, but we definitely aren't there yet. There are hundreds of different kinds that perform better or worse in different applications.
AFAIK all of the big commercial systems that do multiple different types of heat transfer use water to do it, thus bypassing the entire refrigerant selection issue. Right now the most advanced we can do is VRF ("Variable Refrigerant Flow") systems that can individually select air handlers for cooling or heating (i.e. move the heat from one room to another). These are still commercial units and not really available for residential installs.
This enables your hot water heater to use the same circuit to heat water - that decreases your hot water bill to around a third, even in winter as the necessary heat isn’t taken from the indoor air but from the ground.
??? That's excessively long. Our heat-pump dryer takes about 20-30 minutes to do one of our loads.* The dryer invariably ends up waiting for the washer to finish.
* Our loads aren't excessively tight in the machine. You have to allow room for the clothes to tumble loosely thus allowing lots of surface area for evaporation.
Obviously, if every heat pump dryer took 20-30 minutes, you would not hear complaints about that (that’s much faster than my gas dryer).
Every heat pump dryer I looked at on the home center's website is 240V. (Edit: I found one Miele on another home center that was a 15A@120V.)
(That's also why they don't seem to use electric kettles in the US commonly as is normal in 220 volt countries)
I also do want to get a heat pump dryer (it's next on the list after my recently installed heat pumper hot water system), but I don't have quite enough space in the laundry and apart from two or three wet weeks a year I'd mostly only use it to fluff up towels (which is why I don't have a dryer at all at the moment)...
You'd think costs would educate. Do people not talk about living expenses much?
What you do is wait for the A/C to hit end of life (or end of efficient life if new systems are enough more efficient) and replace it outright.
(I once got a quote, in an expensive market, to add an A/C to an existing furnace and, separately, to remove the furnace and add a three-head multi-split heat pump. The two quotes were almost the same price. The equipment is not especially expensive.)
As an aside, many have commented on the claim that heat pumps make more sense with a well insulated building, arguing that it should be the other way around. The reason that you do want a well insulated building is simply that air-to-air heat pumps are limited to typically less than around 8kW heating capacity, and with a well insulated house you can heat a large area with that, with bad insulation you can't, and you would need a much more expensive type - typically not those sold to home owners (or buy several pumps, exploding the costs). In addition to that, a heat pump is more efficient when it doesn't have to run at maximum capacity. The heat pumps sold in the Nordic countries are typically around $3000 including installation. And they're highly efficient.
https://www.amazon.com/dp/B09ZCZSSV8
$5000 is ridiculous for the Gradient Comfort 8000BTU window unit. The Soleus is the only other heat pump window unit I've seen for sale. Midea makes some A/C's that are more efficient because they use an inverter, but they don't do heating. There seems to be a market failure here, given that a bidirectional heat pump shouldn't cost much more than an air conditioner you'd think everyone would prefer a heat pump, especially since it would lower cooling costs and can do lower cost heating in the winter. But nobody is selling them at reasonable cost and quality. They could include a heat exchanger also to bring in fresh air without losing energy. But nobody makes such a thing. Maybe the barriers to entry in this market are high for some reason? Window air conditioners have always kind of sucked (too noisy, encourage mold, uneven distribution of cold, crummy temperature control). I wonder why. It seems wrong.
Seems like the manufacturer just makes junk and hopes they can still keep the money by making it hard to return.
People are happy with this unit in NYC for tiny pre-war construction units that can't use traditional A/C for reasons.
The other unit you link appears to be sold under a variety of brands, look at the comparable products and the button configurations, in all of them the blue light on right is a bit offset upwards:
https://www.amazon.com/R-W-FLAME-Conditioners-U-Shaped-Condi...
This is not unusual. Almost all these compressor-based mechanical boxes, from A/Cs to refrigerators, low end to high end, are made by the same 3 mega companies and white labeled by even the "best" known brands.
https://www.amazon.com/Midea-Cooling-Inverter-Window-Conditi...
But the page also says: "NOTE: heat pump function will not work if outside temp is 41°F or below."
The R-W-FLAME unit has about as many bad reviews as the one I linked. Maybe the reason for the lack of products/competition is as you say they "are made by the same 3 mega companies".
"... half of Phoenix residents are at risk of an emergency room visit or worse if their electricity fails during a future heat wave, according to a recent study. Air conditioning is what keeps people there comfortable—and alive—a growing fraction of the year. The extreme heat already kills hundreds of Phoenix-area residents every year, a number that went up by 25 percent from 2021 to 2022."
Same with cold weather, if the gas/electric goes out during the winter. There's really only a few places one can live with moderate enough weather to avoid those scenarios.
It seems like there’s an important scale issue there. So the risk isn’t really the same everywhere.
People who retire there most likely go up to Flagstaff in the summer, or further north.
Or they just have good A/C.
do you really not see a difference between a place where the event is much more likely to happen for a much longer % of the time than another place where the same event is much less likely to occur?
I 100% disagree with this...
Heat is made by everything, waste heat is a byproduct of all modern things, and there are TONS of easy low cost ways to make heat even it is just as simple as burning something.
Also the body makes head naturally so adding layers to trap this heat does not require continual inputs from an outside resource
Cooling on the other hand is MUCH harder, and electricity is really the only avenue to make cooling. Even if you say use ICE, well that Ice was made at some point by a freezer running on Electricity
IMO hot climate is MUCH MUCH more dangerous than cold, which is why I choose to live in an area where there are only 1 or 2 months of even remotely hot climate.
As I told my last HVAC... Heat I can make 100 ways... Cooling I need central air for...
I grew up around the 38N parallel, gross enough to get too hot in the summer and too cold in the winter. Every winter people froze to death, just the same.
It's not as bad as Phoenix percentage wise, but it's still a risk in the vast majority of places that people in the US live.
My Claim is providing people with emergency heat is FAR FAR FAR FAR easier and cheaper than providing people with emergency cooling.
Do "at risk" people die in the north from the cold, absolutely but I am not sure how that means the cold is worse
As it stands right now, just from my daily activities my waste heat in my home makes my home about 10-15 degrees above ambient. Meaning in the winter if my target temp is 65deg, it would have to be 50 degrees or colder outside before I would even think about running my heat.
In the winter time that means my AC is working hard to not only combat the outside temp but the internal waste heat from computers, cooking, TV's, humans, etc.
Gas-powered fridges and coolers have existed for about two hundred years and are still a normal technology today - often used for camping and off-grid life.
Here's a whole bunch of propane fridges for your viewing pleasure: https://bensdiscountsupply.com/collections/propane-refrigera...
* citation needed.
Unless you have a terribly insulated shelter, blankets, coats, and friends will keep you warm enough to the extent that unless you are not really capable of taking basic care of yourself, you're not dying of the cold when your heat goes out. You can always do more insulation, and you only need so much for your body to keep you warm.
With heat though you run out of things to do.
There is a difference between an impaired person or a person doing something unwise dies of the heat or cold... and there being an environment where there's nothing a healthy adult can do to survive without powered heating/cooling.
I used to work in the Middle East, and their traditional structures with central pool and windcatcher/chimney design remained quite livable even when it was over 45°C outside, with zero active cooling.
Ah, here's an article: https://www.nytimes.com/2017/08/04/upshot/the-all-conquering...
It's pretty crazy because growing up in central/northern Alberta, I never even really encountered air conditioning until I was into my early 20s and moved to southern Ontario (where living without it would be complete hell in the summer, hot humid disgusting "I feel like I'm being smothered in someone's armpit" summers). Our cars never had it and our houses certainly didn't need it; just an open window. Summers were mild and the heat when it came was a dry heat.
But now when I go home to visit there, A/C is everywhere there, and it's frankly needed; the last summer I spent time out at my parents west of Edmonton there were multiple days in a row over 30C and it was frankly quite hellish and them having a ground source heat pump that cooled the house was a godsend. Just the 2-3C difference in peak temperatures from the 80s til now is enough to push it over the edge into new territory.
Sort of makes one wonder how we’re ever going to colonize Mars so we’re not a single planet species.
Or pretty much all Australian cities in summer?
In Arizona, in the middle of summer, you could be buck naked and you'd still overheat (and get burnt, to boot).
That's actually incorrect. Heating takes considerably more energy.
When you're cooling you're looking at a temperature delta of at most 20 degrees C/45 degrees F between outside and inside. When you're heating, it can be easily be twice that. Or even more, in parts of Canada or the Great Lakes states.
Air conditioning is a heat pump and can achieve up to 300% efficiency. Whereas most houses in cold climates use furnaces, which have at most 98% efficiency.
Now that we have more efficient cold-climate heat pumps all of this may gradually change. But as of right now, what you're saying is wrong.
But that's very different than claiming than cooling is more efficient than heating. In A/Cs the ratio of energy (in the form of heat) removed to energy consumed is very low, around 10-15%.
In furnaces the ratio of energy added to energy consumed is around 90%, which was pretty good until the emergence of heat pumps. There almost all the energy consumed is added to the output in addition to all the energy removed from the other side. That's why the efficiency in heat pumps is beyond 200%.
In summary, no. Cooling is not more efficient than heating. But given the temperature differential when cooling the energy consumption is usually higher.
Why is that?
Obviously I'm referring to efficiency in practice. In theory, heating and cooling should be equally efficient for a perfect heat pump, right?
No. You can't directly compare "efficiency" numbers across different energy sources. My understanding is that the efficiency of gas powered electricity generation is around 33%, meaning that powering a heat pump with a COP of just under 3 will be of similar end-to-end efficiency as burning the gas directly in a condensing boiler/furnace.
I'm well aware the figure in my above comment could be off by a decent amount due to transmission efficiency, what specific plants are generating marginal power, etc. But it's at least framing the comparison right.
To a consumer, comparing nameplate efficiencies as you say makes the most sense. I can easily find out how much a joule of electricity and a joule of natural gas cost me. Then multiply those with efficiency to see which is cheaper.
Based on a figure I just saw from someone else describing their setup (1.75 COP at 5 deg F), and taking into account transmission losses etc, the worst case would seem to be significantly less efficient than burning natural gas directly in a condensing furnace.
This isn't meant as some sort of knock against heat pumps! In fact I'm tentatively planning to add a heat pump to my own home within the next several years. Focusing on a worst case is still not an overall comparison of performance, but rather just one data point in the evaluation of a given design.
Multiplying the cost of the energy source by the nameplate efficiency is indeed another sensible way of comparing across technologies. But that isn't what you did in your original comment, where you juxtaposed two different types of efficiency numbers. That was my only point in my original comment.
If I'm too cold and my power goes out I have a lot of options to survive. I can put on more clothes, get under a blanket, light my furniture on fire, etc
If I'm too hot and my power goes out, I die. Once the wet bulb temperature gets above a certain level in shade, there's nothing that can be done to stop me from dying except Air Conditioning.
Hint: Phoenix is at 17% humidity today, even their all time high of 122 doesn’t push the wet bulb temp out of the safe range.
Now include climate change raising the temperature and changing the length and severity of monsoon season, continued development raising the heat island effect.
It doesn't matter what the average wet bulb temperature over the entire coty over a long period of time. It matters what the peak wet bulb temperature is for significant number of vulnerable people. The wet bulb temperature only has to get very high once to kill a large swath of people.
I understand just fine the wet bulb temperature has been within safe levels for the vast majority of people so far. My concern is about the future.
In the 30+ years I have lived in Arizona, I have experienced probably 2 outages, lasting a total of a few hours (one was when a car hit a transformer, the other was when a microburst knocked a bunch of aging poles down).
The last outage I had was like 6-8 years ago.
After a flood/hurricane/nuclear strike, they would provide enough coolness to keep people alive for a few days.
You can use this tool to visualize this: https://drajmarsh.bitbucket.io/psychro-chart2d.html
(Use the Givoni Bioclimatic Chart overlay and select a weather station using the globe icon.)
That said, there are a number of more complex devices which could further reduce how often AC systems need to be used: dew-point (Maisotsenko Cycle) coolers, indirect evaporation cooling, and thermal energy storage to name a few.
Aren't swamp coolers only really useful when the humidity is under something like 50%? I guess I'm assuming you're talking about the US, but I don't think "vast majority" of people live in such areas. A quick search for average humidity of US states in July and August shows many of them have an average daily humidity of over 50%.
It certainly rules out every place I've lived on the east coast (Richmond, Virginia, Long Island, and the Boston area), as the humidity in those places is usually at least 60% at the height of summer when most people actually use their AC.
As a side note, I suspect most people overuse their air conditioning and don't let their bodies adapt to the warmer summer weather. It's weird how many people keep their houses under 75 °F when the heat index is only in the mid 80s.
They are less effective, but still work. As long as the dew point is ~72 degrees, or lower, they can still cool enough to do the job (although of course not to the extent of an AC). But yes, ultimately it comes down to people being ok with not setting the AC to 68 degrees when it's 80 degrees out, and using the minimal amount of cooling necessary to be comfortable.
Then, what's the point? If you still have to have gas lines and infra, just use the gas. It's vastly cheaper.
A) Not everywhere
B) Heat pumps can be powered with solar, reducing costs even if your gas would normally be cheaper
C) Some people are willing to spend a little more if it helps push electrification forward, for environmental reasons
It's not a little more though, that was the point. In my area, California, it's about 4x more. Gas here is so cheap, it's almost free.
Anecdotally, I don't know anyone who's opted into the "green energy" plans offered by the area's utility providers - because they all cost a lot more than regular.
People talk a lot - but their bank account dictates their actual decision making. Running a heatpump seems very expensive for a lot of the country, with negligible gains.
Natural Gas isn't exactly what we would call "dirty"... seems like a min-max issue, with people forgetting there's still areas burning coil and oil for electricity production.
> Heat pumps can be powered with solar
Not in the dead of winter you can't... not everyone lives in big cities folks, and where it snows, it gets quite cold.
There will be a feedback loop once that really starts: individual prices go up because infrastructure costs remain the same, but less people are using gas. Once natural gas prices go up, people will switch to more efficient appliances, or switch to electricity. Forcing prices to go up some more to make up for infrastructure costs.
I agree with you about people following their wallets and that's why people will want to change to heat pumps when gas becomes too expensive. Remember the prices in December?
Minimizing your gas use?
Depends on where you live
One thing people tend to do when they look at heat pumps is look at the typical extreme low for the year and size the heat pump based on that. But even if you touch -20 a few times a year, your heat pump doesn't need to be sized to heat in a constant -20. If you hit -20 once or twice per year then it's usually only for a few hours and the lowest that you really need to heat through is usually much closer to -10 or higher.
But, yes, if you're in a climate that sees frequent and sustained temps of -40 then a heat pump probably isn't for you or the rest of the Canadian Prairies.
You can also do heat pump for 90% of the time and emergency heat as oil/gas/wood stove.
Do you mean real -40? Or wind chill "-40" which doesnt affect HP?
Edit: Edmonton?
- It's probably going to be more expensive than heating with natural gas if you're in the northern US - at least as things are today.
- A modern/high tech heat pump capable of heating when the outdoor temp is < 10f / -12c is likely going to be quite a bit more expensive than a standard AC unit - making it even more difficult to justify financially
- A natural gas furnace can keep you warm (and keep your pipes from freezing/bursting) even if there's a power outage. It doesn't take much of a generator to run a furnace/blower fan.. but good luck staying warm with ONLY a heat pump in those circumstances.
The one thing that can really help improve the financials of getting a heat pump is if you intend to install solar power at some point in the future. Depending on your power company, you may be able to generate enough credit in summer with excess generation to pay for heat the entire winter. I'd still go with a heat pump AND gas furnace for backup though.
Thankfully, this isn't too expensive of an option to do. Gas furnaces are cheap. Heat pump that isn't sized to go to -40F/C is also pretty affordable. The crazy high SEER ratings drive up the price.
Modern heat pump systems have an outdoor temp sensor and will avoid even trying the heat pump if it is too cold outside. Your installer should be able to adjust that setpoint. How low it can go depends on the refrigerant and rating... in the US higher SEER ratings often also means it can extract useful heat at lower outdoor temps.
tl;dr: The heat pump function is a trivial bit of material addition to a standard A/C and saves you gas/electricity even if it is only used for part of the cold season. There is no reason not to use one.
I say this as someone who recently helped undo the damage after an inept HVAC technician replaced someone’s thermostat (for $500, thanks California prices) and did it wrong. The quality of the instruction manuals is low, and the quality of online resources about how conventional HVAC controls work is lower.
As far as I can tell, the theory is that HVAC systems used to consist of a bunch of discrete components, strung together, with control power coming from one or two transformers or thermocouples [0], and essentially no logic in the equipment. A relatively modern heat pump may well rely on a mechanism in the thermostat to protect the compressor. The actual equipment contains nothing resembling a microcontroller.
[0] Yes, the actual power available from the equipment to the thermostat may be negligible, and old thermostats were mercury switches on bimetallic strips that were powered solely by temperature changes in the room.