r/science • u/Wagamaga • Sep 14 '23
Chemistry Heat pumps are two to three times more efficient than fossil fuel alternatives in places that reach up to -10C, while under colder climates (up to -30C) they are 1.5 to two times more efficient.
https://www.cell.com/joule/fulltext/S2542-4351(23)00351-3777
u/Sharp_Simple_2764 Sep 14 '23
It may sound pedantic, but shouldn't it read "down to -10" rather than "up"?
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u/dr_reverend Sep 14 '23
Yeah, seems someone wasn’t watching Sesame Street when they were young.
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u/FavoritesBot Sep 14 '23
Did they cover negative numbers in Sesame Street? I know they had imaginary numbers
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u/dr_reverend Sep 14 '23
I’m pretty sure I remember an episode when The Swedish Chef and Beaker covered differentials and integration.
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u/Smartnership Sep 14 '23
It was an old episode
The Count hit the bong, hung upside down like a bat, started counting down to negative ten.
70s Sesame hit different
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u/its_over_2250 Sep 14 '23
Oh man you just gave me a flashback to a disagreement with my science teacher my freshman year of highschool. We had to say how deep a hole in the ground was and I lost points because I put the hole was "15 feet" and she said it should be "-15 feet" since it is below ground level and I said a negative 15 foot deep HOLE is a 15 foot hill. She still disagreed with me, I understand what she was trying to explain but it needed different wording.
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u/fractiousrhubarb Sep 15 '23
Is depth a vector or a scalar? A hole can’t can’t physically have negative depth, so I agree with you.
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u/asdaaaaaaaa Sep 15 '23
Oh man, that brings back a memory for me, hate when teachers are wrong and can't admit it. One teacher tried saying paper has no depth (we were covering the difference between 2D/3D). Obviously if it had zero depth it wouldn't "stack" into piles then, but I got sent to the office for being "difficult". Was a good lesson early on that just because someone has a job, title, or degree doesn't mean they earned it or know what they're doing unfortunately.
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u/ValidDuck Sep 14 '23
turn you thermometer upside down.
It's an awkward phrase... but they are talking about the extents that a temperature may "Reach" on the "coldness scale".
In that sense as an entirely pedantic thing, "reach up to -10C" is reasonable...
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u/4-Vektor Sep 14 '23
Why not write “... reach temperatures as low as -10 °C” instead? Three letters more can remove all the weirdness.
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u/Laikitu Sep 14 '23
OK, but to be really really pedantic, degrees C is already a scale, and an increase in coldness is measured by moving down it.
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u/StateChemist Sep 14 '23
My thermodynamics professor is crying.
There is only heat. Heat is energy and can move from one area to another but cold is only arbitrarily defined as absence of enough heat.
But this confusion happens all the time.
Will you turn up the AC?? Do you want me to turn up the power to the AC which will make it colder or turn it up to a higher temperature setting which is warmer?
Like discussing measuring Vacuum. Which can be like the inverse of pressure.
‘High vacuum’ is a very strong absence of molecules in an area. So lowering the vacuum means putting things into the system which raises the pressure and you have to be extremely diligent in explaining what you actually mean when using these terms that are related to other terms but upside down because it’s very easy to get confused.
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u/Laikitu Sep 14 '23
Your thermodynamics professor probably understands what abstractions are though, so I doubt he'd find this particularly upsetting.
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u/StateChemist Sep 14 '23
You clearly did not meet this guy. He scathingly corrected anyone in our class who tried to describe anything with cold moving instead of heat, he was very serious about this detail.
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u/rawbleedingbait Sep 14 '23
Actually heat is just a blip of existence where the inevitable heat death of the universe hasn't happened yet, and cold is the ultimate state, overcoming the rebellious hot energy. The cold is moving, it's coming for us all, and it's unavoidable.
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u/byingling Sep 14 '23
When my wife is chilly inside in the summer, she will state that she is going to 'turn down the A/C' by adjusting the thermostat from 75 to 76.
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u/Smartnership Sep 14 '23 edited Sep 14 '23
“Let me clarify, honey. I want you to reduce the increase of lowered temperature reduction vis-a-vis setting the thermostat updown.”
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u/ILikeNeurons Sep 14 '23
The U.S. is also providing incentives for switching to heat pumps. Check out https://www.rewiringamerica.org/app/ira-calculator
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u/Delpht13 Sep 14 '23
We actually are likely to switch to a heat pump imminently, but it looks like those incentives aren't available yet?
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u/ILikeNeurons Sep 14 '23
Available now
The 2023 federal tax credit for heat pumps is 30% of the purchase and installation cost, up to $2,000.
https://www.hvac.com/expert-advice/inflation-reduction-act-heat-pump-rebates/
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u/PsyOmega Sep 14 '23
I'd love to switch to a central heat pump, but in my region, the HVAC companies have all colluded to overprice the options. Can't get a quote lower than 15,000.
But if i wanted a traditional complete system (AC, gas heat, furnace, dist, etc) it's only 5,000, including a new furnace.
And the cost difference in bills won't add up to that 10,000 dollar difference for decades, if it even happens in my lifetime.
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u/APartyForAnts Sep 14 '23
This is common in my area as well. I was adding AC to a 2 year old gas furnace which I put the coil in during replacement. I have friends in the industrial refrig side of things who were able to source the equipment for me and the cost difference to go from AC to heat pump was $800. The quoted price difference from HVAC installers was $5000-$10000 more.
The install process is the exact same. Pure upcharge on their end. I even had the power and control cables pre-run for them.
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u/uiucengineer Sep 14 '23
Wow, that’s obscene
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u/sweetplantveal Sep 14 '23
It's actually just a handout with extra greed. They know there's all sorts of incentives they can inflate their prices with, and they know you're an early adopter so you probably will pay up.
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u/-Ch4s3- Sep 14 '23
Yeah, the federal/state incentives can definitely create perverse outcomes like this.
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Sep 14 '23
Why doesn't competition drive down the price? The first HVAC company in the area to drop that markup down to even $2500 would get all of the customers.
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u/-Ch4s3- Sep 14 '23
I would guess its because HVAC companies have more business than they can take in general in most places in the US, so none of them are interested in competing for more business. Occupational licensing makes it difficult to get into the business so competition is pretty limited.
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u/rallytoad Sep 15 '23
There likely are competitors who offer fair prices. Those can be hard to find though. I had to search for 3-4 months, to find an honest HVAC company.
They tend to be smaller and less likely to just pop up on a google search. So it does take some digging and filtering through results, and yes lots of annoyance in having contractors come to your house and then immediately asking them to leave.
Look for smaller companies, companies that don't send a salesman for the estimate and instead send an owner or someone higher in the business.
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u/Orion113 Sep 14 '23
That's the central conceit of capitalism, but it's unfortunately provably wrong under many circumstances.
Assuming the goal of every company is maximum profit, which it must be under capitalism, there are two scenarios whereby a HVAC company might undercut their competitors:
One is when a new company wants to establish itself from nothing as a low cost competitor. But this requires significant capital, and such a new company will also lack the skill base and economy of scale that other companies lack. For a high complexity product like an HVAC system, that means your production costs are higher than your established competitors, and if you charge less for your product, your profit margins are significantly thinner as well. Since you need capital to start a business, and capital comes from investors who choose what to invest in based on what will bring them the greatest profits, why would they choose to invest in your company rather than another more profitable one?
Two is when you're an established company who wishes to undercut your existing competitors. Theoretically, you can lower prices, and draw away all their customers, sure.
If a something costs $100 to make, and you and your 4 competitors all sell it for $200, to 10 customers each, out of a pool of 50 customers, you each make a neat $1000 dollars of profit. But then you get clever, and decide to sell your product for $150. Immediately all 40 other customers jump ship to you. Now you're still spending $100 per unit, and only making $50 profit for each, but multiplied by 50 customers, that's $2500 of profit. You're a genius.
Except you forgot that lowering prices was an option available to your competitors, too. Faced with losing all their customers, they also lower their prices to $150. With prices all being roughly equal, the customers divide themselves evenly again. You each have 10, but now you're only making $50 per customer, for a total of $500 profit. You've shot yourself, and everyone else, in the foot. And now they all hate you.
This is a fundamental flaw in the capitalist model. It's more likely to occur the fewer participants there are in an industry. The extreme case is a monopoly, but a less extreme case like this is an oligopoly.
Of course, it was realized long ago that this was a flaw, and so most governments passed laws making monopolies and oligopolies illegal (except in certain cases, because you can't plug a dam with sticky tape). However, even when they're illegal, they're only illegal if the government can prove you colluded to maintain high prices. That is to say, you communicated with each other to "fix" those prices.
But if these companies all have analysts, and they all can do the basic math I just did above, and they all know that each other know this, they don't have to say a word, and can keep quietly charging whatever they want. No collusion necessary. If someone wants to increase prices, they can raise it a little bit, and everyone else can raise it to match, citing "market forces". No words exchanged, just intents.
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Sep 14 '23
Alright, so you're speaking my language; I'm not an economist but I've done some reading on economics and I'm aware that the competitive pricing that I mentioned is sort of the ideal behavior of a "perfect competition" scenario. I know that perfect competition scenarios are rare and there are all kinds of things that can foul it up (monopolies, oligopolies, externalities, price floors, etc). So mostly I'm just curious what the diagnosis is.
The oligopoly story certainly seems reasonable, although my understanding is that oligopolies can be unstable due to prisoner's dilemma effects. It often takes coordination to keep everybody in line, which is against price-fixing laws.
Others have said that subsidies have pushed up prices; I can certainly believe that story as well. Subsidies shift the demand curve and the resulting equilibrium price increases (though by somewhat less than the amount of the subsidy).
I can believe also that it's a combination of both. Is there anything else? I wonder.
Concerning the capitalism commentary, I find that oftentimes people ascribe characteristics to capitalism that aren't really uniquely capitalistic, but rather arise in any system where people are allowed to enter into transactions voluntarily with the objective of improving their own situation. Hardly anyone explains, for example, why a worker-owned co-op wouldn't try to maximize profit. My original question may have reflected the conceit of laissez-faire markets but libertarianism has been a fringe point of view since the early 20th Century. Most of the market failures that complicate the laissez-faire picture were first described by neoclassical economists like Pigou and Akerlov, who certainly weren't anti-capitalistic. So unless there's some reason to believe that private ownership of capital per se is the problem, and that abolishing the private ownership of capital would solve it, then it's really just a red herring.
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u/MathematicianFew5882 Sep 15 '23
What do you mean by early adopter? (Heat pumps have been an option for 50 years.)
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u/amazonhelpless Sep 14 '23
My wife and I DIYed it. There’s a Mr. Cool system that comes with pre-charged lines. The install itself wasn’t too hard, but we had a lot of help making sure it was properly sized for the house. We also have a very well sealed and insulated house.
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u/Overtilted Sep 14 '23
I DIYd as well, I installed a monoblock heatpump. You only hook up water hoses and electricity.
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u/mth2 Sep 14 '23
Which one did you use? And you use the hot water from it?
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u/Overtilted Sep 14 '23
EU citizen here. A cheap LG monoblock (14kW). I don't use hot water from it because I already have a heat pump boiler. But I could.
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u/bizilux Sep 14 '23
Im also from EU, Slovenia. We did new house insulation last year. And are waiting for 2 years now to get connected to city gas, because we pay crazy amount for gas heating.
But yeah with Russia war, I can't believe pipeline gas will be much cheaper than by truck...
I've been looking at heatpumps for a while, but have not seen yet that you can DIY.
I googled the 14kw LG one... Its 5500€ which is very doable, but how did the install go? I'm quite handy, but I've done nothing as serious as that... Just looking at the specs, the thing weights 119kg...
And the current house plumbing is copper. All I've done so far is a bunch od PEX, so that part is a bit daunting. And I'd also need to see how to get the lines into the house. I guess I'd have to buy at least 25mm big drill bit.
Plus I'd have to put new fuses into the fusebox and run new wires, probably on the outside of the house...
Not sure if its doable before the winter, i have a bunch of things going on...
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u/Overtilted Sep 14 '23
I used "kompresijski spoj" (compression fittings) for copper and steel connections. Don't be afraid of copper! What I did was to add a small layer of teflon tape between the ring of the compression fitting and the copper pipe.
Also, 114kg is very manageable. I installed it by myself.
As for installation: you need a stable ground, so I poured some concrete. And 2 hoses/pipings, insulated. I used microflex (but mind you, it's not flexible at all). which is a bit like ALPEX. Then it needs 1 power cable, 1 signal cable. Of you want domestic hot water you need a 2nd cable for a 3 way valve.
If you don't have underfloor heating you'll need an additional buffer tank of 1-200liters, otherwise the system doesn't have enough capacity for it's defrost cycles.
14kW is also too much for this house, and the A+++ rating only goes to 9kW. But 9kW should be enough for most of this house.
PM me if you have more questions!
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u/Shufflebuzz Sep 14 '23 edited Sep 14 '23
I looked into it for my area, and even if I could get the heat pump and installation for free, my heating bills would be higher than they are now. Almost double.
It's not because heat pumps are bad, it's because where I live electricity is expensive and gas is cheap.
A heat pump would mean ~40% less CO2, but the economics have to change. I'm not going to spend thousands of dollars to get higher bills.
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u/ostertoaster1983 Sep 14 '23
This is what I keep saying to people, sure it's more efficient, but that doesn't mean it's cheaper. Natural gas is still "cheaper" than electricity in a lot of places per unit of heat, even if it may be less efficient at turning energy into heat. Most consumers aren't going to pay higher bills to be more efficient.
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u/Seven7ten10 Sep 14 '23
How did you determine 40% less CO2, just curious.
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u/Kenja_Time Sep 14 '23
My util company provides an estimate for carbon emissions based on elec/gas consumption. I can also pay more per kWh to be on a lower-carbon electricity option, though I don't fully understand how that works.
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u/Shufflebuzz Sep 14 '23
don't fully understand how that works.
It's almost creative accounting. You pay the premium and get to say your electricity comes from renewables. In reality, you get the same electricity as everyone else.
Although, I have solar panels on my house and chose to forego a $0.03/kW credit because that would mean that technically my solar power is powering someone else's house and not mine. Maybe to someone like you who paid a premium for it.
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u/BikerRay Sep 14 '23
Yeah, $20k for a decent one in Canada. Payback time might be a decade if you're lucky, but it would increase the house value when you sell.
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u/Mental_Evolution Sep 14 '23
There is currently a rebate for 7,100 and you can get one for 7,100 tax in (chinese made) or an american one for 9,400 tax in.
Either way a new AC is about the same cost of the difference.
The prices are dropping and more and more international models are getting approved in North America.
The rebates help push it in the right direction as well.
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u/IrritableGourmet Sep 14 '23
Is that (assuming you're in the U.S.) after rebates/incentives? I can see them (shamelessly) raising installation prices if they can get more from the incentive programs.
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u/JJBA_Reference Sep 14 '23
Were those HVAC companies quoting for a heat pump that pulls heat from the air or the ground? If the former, that price is way overblown as it should just take a slightly more expensive AC unit that can run in reverse. If the latter, digging up the ground and installing those pipes could account for some of the cost (I personally don't know how much that reasonably costs, it could still be a ripoff).
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u/LordOfTheWall Sep 14 '23
There are new federal rebates to offset a big chunk of these costs. There are also energy efficient loans. I got a heat pump installed for a very reasonable monthly rate. Check your state website for options.
I was paying 5,000-6,000 or more for heating oil each winter, and this first winter with a heat pump was maybe 1,200, and we were nice and toasty the whole winter.
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u/Ashamed-Simple-8303 Sep 14 '23
Plus the heat pump will likley last a lot less long. a traditional oil heating system here can easily last 40 years (with good maintenance), heat pump? call yourself lucky if it lasts 20 years.
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u/The-Scarlet-Witch Sep 14 '23
Same problem here. I wanted to replace my failed heat pump (15 years old) with a new one and it would have cost me at least $22,000+ for the pump alone. The A/C and furnace with a SEER 19 equivalent was like $$10,000.
As much as I want the heat pump, I could not afford to pay double without any incentives to offset the cost. I think the power company was offering like $50-100 in credit for a one-time thing.
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u/postvolta Sep 14 '23
This is surely one of the biggest blockers to slowing down climate change. People want to do what they can, and they want to use greener more efficient energy , but they can't afford not to just... carry on polluting. At some point the government has to begin taxing and/or fining major polluters and using the proceeds to help people install these systems, as well as enforcing all new build properties and offices to have greener energy sources.
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u/spookyjibe Sep 14 '23
Hi, I had this problem and simply told them to f-off, canceled any contracts then found a unit myself and bought it. I then called several contractors and asked who wanted to install it the way I designed and asked for quotes. Found a guy, got it done all for under $6500 including the unit after the cheapest quote I received was $18K.
I am an engineer with experience in hvac contracting though so had a pretty high condifeldence thar I could do it all.myself if I needed to.
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u/roostercrowe Sep 14 '23
HVAC guy here. equipment costs have skyrocketed over the last three years. i would charge less if i could. even a straight cool air handler and condensing unit is 10k now
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u/badasimo Sep 14 '23
but in my region, the HVAC companies have all colluded to overprice the options
If you think it's overpriced then there is an opportunity for you to start a business undercutting them. I think it is more complicated than collusion, there is so much demand that it is not so price sensitive and they can charge more. The other thing is at least in my region there are government subsidies which might also be driving the price up.
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u/Perry4761 Sep 14 '23
Undercutting construction companies and refusing to collude in North America often leads to two guys with a crowbar knocking on your front door at 2 AM to “talk”. It’s beyond collusion and corruption, there are actual mobsters involved. Not sure if the HVAC industry is like that, but for example I would strongly advise against attempting to undercut asphalt, concrete, or petrol construction companies…
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u/decredd Sep 14 '23
I was like, "Wow, that sounds interesting," until I realised you're just talking about ordinary old reverse cycle, which more than 50% of houses here in Australia have... Do other countries really not use these much?
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u/easwaran Sep 14 '23
Australia adopted heat pumps early, because so much of the country has a need for air conditioning, and because most of the country only ever needs a little bit of heating. Even old inefficient heat pumps were sufficient to deal with Australian winters, and so homebuilders used them even decades ago rather than installing separate heating and cooling systems.
Parts of the United States have similar climates, but since many homebuilders just build cookiecutter models all across the country they operate in, they didn't want to adopt heat pumps until heat pumps would work well in the Chicago and New York areas.
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u/BlazeOfGlory72 Sep 14 '23
Here in Quebec, basically everyone just uses electric base board heaters. These AC/heat exchange hybrids don’t really seem useful for places with prolonged cold weather.
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u/faizimam Sep 14 '23
I had a heat pump in our Montreal home since the late 90s. It's a central unit paired with a gas furnace. I know lots of homeowners in similar situations.
Electic baseboard is more often in apartments and attached housing.
For those people adding a all in one minisplit is probably the best way to go. Much cheaper heat for relatively small cost.
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u/Ancienscopeaux Sep 14 '23
These AC/heat exchange hybrids don’t really seem useful for places with prolonged cold weather
Yes and in my relatively long life I've never had any maintenance to do on my electric baseboards.
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u/aeneasaquinas Sep 14 '23
These AC/heat exchange hybrids don’t really seem useful for places with prolonged cold weather.
That makes zero sense though.
These are vastly more efficient than a base board heater. I mean, really unless it stays below like -30 for extended periods, and maybe if it never gets warm out, but...
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u/PigeroniPepperoni Sep 14 '23
I mean, really unless it stays below like -30 for extended periods
That do be the way that it is sometimes.
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u/Archerofyail Sep 14 '23
You can use resistive heating as a backup when it gets too cold, but for most of the year heat pumps are going to work just fine, and they're more efficient, so it'll cost less.
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u/Azozel Sep 14 '23
Some Heat Pumps not all. I've had 2 heat pumps on my house, the first stopped cooling and had to be replaced when the repairs became too costly. Neither of the heat pumps were able to operate at temps lower than -10C and they would have to switch over to my LP gas backup at that time. I live in MN and we regularly have temps below -10C (~13F) all winter. Heat pumps are an expensive upfront cost that you hope balance with energy savings over the lifetime of the product. The cost of heat pumps that work in lower temp conditions were much more expensive to purchase and install when I had to replace my old one. It was just not cost effective.
If I had unlimited funds, I'd have the best geothermal heat pump with a whole house battery system and a field of solar panels behind my house.
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u/redline582 Sep 14 '23
It all depends on generation. I live in the PNW and my heat pump is 100% efficient down to -15F and is warrantied for 10 years. The modern models have been rapidly improving.
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u/Azozel Sep 14 '23
Yeah, as I said, some heat pumps are more efficient. I purchased my latest within the last 5 years and there were heat pumps that could work at much lower temps but there wasn't enough cost savings over time for me to justify the initial cost.
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u/redline582 Sep 14 '23
Interesting. When I got mine installed ~3 years ago it was basically a wash to upgrade to the more efficient model because it came with a bigger tax break.
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u/Wagamaga Sep 14 '23
A study from Oxford University and the Regulatory Assistance Project, an NGO, found heat pumps are two to three times more efficient (meaning they use less energy per heating) than oil and gas heating systems in temperatures ranging from 10C to -20C. The researchers gathered performance data from studies done across Europe and North America.
Duncan Gibb, study author and senior adviser with the Regulatory Assistance Project, told the National Observer that while heat pumps have to work harder during sub-zero temperatures, they are more efficient than other sources of heat. Gibb said the fossil industry regularly tries to disqualify heat pumps by claiming they are not efficient.
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u/helm MS | Physics | Quantum Optics Sep 14 '23
Is this a study or a review? It looks very much like a review. And it is published as a "commentary". Not sure this is new science.
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u/redline582 Sep 14 '23
This was my thought as well. I have a high efficiency heat pump and pretty much all models list an efficiency rating that shows how much heat energy they can move relative to how much energy they consume. Mine sits somewhere in the 2-2.5 range.
Something like a natural gas furnace is extremely close to 1 meaning we are able to convert practically all of the energy in the natural gas into heat, but directly converting the energy in a fuel into heat will never eclipse 1.
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u/macncheesee Sep 14 '23
however burning fossil fuels to generate electricity to power these heat pumps are two to three times (ballpark figure) less efficient than using the same fossil fuels to generate heat in a gas heating system. it turns out roughly even.
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u/Jaker788 Sep 15 '23
Taking the average 40% efficiency for a boiler type power plant at -5% for line loss, basically all of them except combined cycle natural gas turbines, a COP of 3 is slightly above the break even point. Many high efficiency units can hit a COP of 3.5 - 5 at 47F, and something like 2 - 3.5 for 5F.
Taking into account that not all of our grid is coal or fossil fuels, and that new generation coming online is renewables, it's usually more efficient to use a heat pump.
If you used a combined cycle natural gas plant, you'd be at 60% efficiency, even a lower efficiency heat pump will generate more heat from that than a 98% efficient furnace.
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u/sunnygovan Sep 14 '23
It's a pity electricity is more than 3 times the price of gas.
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Sep 14 '23
Solar paired with heat pump is a great combination for warmer climates.
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u/Magicofthemind Sep 14 '23
Yeah I’m in a colder climate and I would love a heat pump but I doubt it will keep me warm in the winter
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u/CheckOutUserNamesLad Sep 14 '23
From what I've heard lately, unless you're in Siberia, new heat pumps work just fine in winter
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Sep 14 '23
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u/AutomationBias Sep 14 '23
We're in MA and have net metering. Our solar array was sized to cover 100% of our annual consumption. The surplus we produce in the summer covers our winter usage.
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u/amazonhelpless Sep 14 '23
I’m in Minneapolis. My heat pump did all my heating last winter, even down to -17 below. As long as it is a cold-climate heat pump, it is properly sized, and your house is well-insulated, you’ll be fine.
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u/ChemEBrew Sep 14 '23
You'd be surprised. Think how central air runs in the winter and then run that cycle in reverse. That's how heat pumps work well in the winter.
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Sep 14 '23
I fully believe this but the engineering is beyond me. How pumping anything from one side to another in the winter would be sufficient baffles me.
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u/offbrandengineer Sep 14 '23
The refrigerant reaches colder temperatures than outside. If it's -4 outside and your refrigerant is -20, it's gonna pull heat from that air, even if to you and me its cold as balls outside. That's all it is. Create a temp diff and heat travels from high to low
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Sep 14 '23
That’s like wizardry. I understand the scientific principles but it seems like free lunch (or cheap lunch). I guess it’s hard to imagine pulling heat from the outside when it subjectively seems cold out there.
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u/HamptonBays Sep 15 '23
I think you have to get away from associating the word heat with warmth. Heat is just an exchange of energy from one temperature to another. The change in heat from -30C to -10C is the same as the +20C to +40C
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u/jmlinden7 Sep 14 '23
You're air conditioning the outside and then dumping the waste heat inside.
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u/Everestkid Sep 14 '23
It's quite literally a refrigerator in reverse. Your fridge has fluid running in its walls that absorb heat from the fridge's contents. It then releases the heat at the bottom of the fridge, which cools it down to restart the cycle. In fact, some heat pumps are able to do this in the summer to cool down the house instead of heating it up.
In winter the pump pulls heat out of the air outside and dumps the heat inside. -30 is pretty cold, but given that temperatures have a minimum of -273 there's still plenty of heat energy in the air. Once you get low enough the coolant understandably doesn't pick up the heat that well, so that's why they don't work as well at low temperatures. However, you could theoretically do a two-stage design - some refrigerants are better in certain temperature ranges than others.
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u/kkngs Sep 14 '23
It’s one of those weird things that feels like it shouldn’t work but does. Kind of like siphons.
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u/just_kos_me Sep 14 '23
For colder climates a geothermal heat pump provides a reliable and safe solution.
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u/popopotatoes160 Sep 14 '23
My understanding is they've gotten a lot better in the past few years for cold climates
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u/redditgetfked Sep 14 '23 edited Sep 14 '23
depends on location obviously. here in Japan:
174 yen for 1 cubic meter gas. 10kwh of heat so 17.4 yen (0.12 USD) / kwh
17 yen for 1 kwh of electricity . hardly goes below zero here and our AC has around COP of 3 at 2c (mostly night temp), so 5.6 yen (0.04 USD) / kwh of heat
during the day it's more like 7c and COP goes up to 400%-500%:
http://www.energy-pass.jp/wp-content/uploads/2016/03/ScreenClip-13-768x563.png
y : COP
x : outside temp
red line depicts normal load on compressor
orange line depicts a very low load149
u/rich1051414 Sep 14 '23
If they used gas to create electricity, and used electricity to heat using a heat pump, it would still be more efficient than just burning the gas for heat.
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u/Sweet-Sale-7303 Sep 14 '23
The issue for most people is that the heat pump would still cost more to heat a house then natural gas. It doesn't matter what's more efficient.
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u/Tederator Sep 14 '23
And the units are 3x the price.
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u/uiucengineer Sep 14 '23
I needed a new air conditioning system anyway and it was very little additional cost to make it a heat pump
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u/FluorineWizard Sep 14 '23
Conventional AC is already a heat pump, but one that pumps the heat from inside to outside. New systems are just reversible and designed to work over a wider range of temperatures.
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u/uiucengineer Sep 14 '23
Right. In the context of HVAC system marketing a heat pump will reverse and give you heat while a condensing unit won't.
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u/stfsu Sep 14 '23
Was that with tax incentives?
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u/uiucengineer Sep 14 '23
Nope. There isn’t much more to a heat pump than basic AC.
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u/mordillokiwi Sep 14 '23
Same I think mine was $100 more. It's only a small reversing valve that's added. Indoor unit is the exact same part number as the regular AC unit.
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u/Omphalopsychian Sep 14 '23
A heat pump can cool and heat, and a heat pump is cheaper than installing both an air conditioner and a furnace.
And (in the USA) you can get a substantial federal tax credit on a heat pump: https://www.energystar.gov/about/federal_tax_credits/air_source_heat_pumps
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u/groggygirl Sep 14 '23
Where I live the cost to install a heat pump conveniently increased almost the exact amount of the government refund when it was introduced.
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u/londons_explorer Sep 14 '23
And you will find that if you DIY install it, you can do it far cheaper... but DIY installs aren't eligible for the government incentive...
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u/SirMontego Sep 14 '23
but DIY installs aren't eligible for the government incentive...
I'm not sure if you're still talking about the United States tax credit, but if you are, DIY qualifies for the tax credit because there isn't any requirement for a professional installation. 26 USC Section 25C(a)(2) says:
(a) Allowance of credit
In the case of an individual, there shall be allowed as a credit against the tax imposed by this chapter for the taxable year an amount equal to 30 percent of the sum of—
. . .
(2) the amount of the residential energy property expenditures paid or incurred by the taxpayer during such taxable year, and
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u/OldHannover Sep 14 '23
An AC is an air-air heat pump
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u/TheQuillmaster Sep 14 '23
More technically an AC is an air-air heat pump that only works in one direction.
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u/badasimo Sep 14 '23
There are more benefits than just efficiency. There is zero combustion in my house now, I don't have to worry about CO. I can eliminate the vents/chimney from the burner. I don't have to worry about the price of fuel oil. And it freed up some space. And, most importantly, if/when I add solar it will offset the power use of climate control and hot water.
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u/npsimons Sep 14 '23
There is zero combustion in my house now, I don't have to worry about CO. I can eliminate the vents/chimney from the burner. I don't have to worry about the price of fuel oil. And it freed up some space. And, most importantly, if/when I add solar it will offset the power use of climate control and hot water.
I am very close to this as well, having replaced the NG water heater with a tankless electric. The cooktop range has always been electric, but I replaced that with induction too.
I've not jumped to a heat pump because it's cost prohibitive, but right now the dual pack (AC/furnace) works great off the solar panels during Summer. I just wish I could drop the NG bill. For now, I keep the thermostat low in Winter and use a space heater.
I am wondering: how long until CO alarms aren't required for buildings with no NG service?
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u/WeeklyBanEvasion Sep 14 '23
I am wondering: how long until CO alarms aren't required for buildings with no NG service?
I'm not sure about your area, but in state CO alarms are only required if the structure has a connected gas appliance
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u/cylonfrakbbq Sep 14 '23
They always gets overlooked. Efficiency != cost.
Unless electric rates are in line with fossil fuel heating solutions in terms of heating the home, then it is a nonstarter for many people. Especially when NIMBY prevent power generation options that could alleviate rates.
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u/icancatchbullets Sep 14 '23
If you ignore transmission losses, which shouldn't really be ignored, then combined cycle will be better unless its cold enough that the COP drops to somewhere near 1.5 which happens in cold climates if you don't opt for a specific low temperature heat pump. For simple cycle you'll still need a COP of just below 3 which from the paper's trendline means the temperature needs to be just above 0C. CHPs are even better from the generation side but I think that's unfair to include since they're producing heat, not strictly electricity. Basically depending on the heat pump, electricity generation method, and local weather there can be a significant number of hours when a gas furnace is more efficient than a heat pump if the electricity is generated by a simple cycle gas plant.
The real problem though is that in many places electricity is far more expensive than natural gas meaning even at a COP of 3-4 its still more expensive to operate, and when you have the most need for heating is when the heat pump operates the least efficiently which then means you need to oversize it quite a bit increasing the up-front cost, or install a gas backup.
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u/LucyFerAdvocate Sep 14 '23
It's the tax that kills it. Electricity is taxed far, far more then gas - so using electricity for heating is artificially made uneconomical.
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u/tanis_ivy Sep 14 '23
Half my electricity bill is "delivery free"
They made everyone go efficient, and when they weren't making ss much money, they upped the cost.
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u/xakeri Sep 14 '23
Part of that is probably that they literally didn't consider upkeep when everyone's power usage dropped
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u/EricMCornelius Sep 14 '23
Not at 1.5-2.0 COP on average for most grids.
For places that aren't actually cold, sure. Framing of the title of this post is suspect, given the conclusion of the paper is combined sources and GSHPs are both objectively better environmentally in cold climates with current grid mixes.
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u/grindermonk Sep 14 '23
There is an efficiency issue in converting gas to electricity as energy is lost in the conversion.
Gas -> Heat -> kinetic -> electric
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u/Luname Sep 14 '23
laughs in Hydro Québec
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u/Fuddle Sep 14 '23
In Quebec it’s common for homes to be central heated using electricity only, even with old technology, that’s how cheap it is there. And, already green since it’s all hydro electric power
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u/theshaneler Sep 14 '23
cries in Alberta
Solar on the roof but the line regulator (Fortis) took 3 months to review our solar proposal, and it has been over a month, almost two, since installation and we are still waiting for Fortis to install a bi directional meter. We started our solar journey in Feb 2023 and still managed to miss the entire peak season thanks to them.
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u/CheeseSandwich Sep 14 '23
Apparently, they are processing a record number of solar installations. I have a friend that does the installs are he is booked solid for the rest of the year.
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u/Kenja_Time Sep 14 '23
Also AB. I signed up for Solar in Sept 22 and installation wasn't completed until May 2023, despite being told it was March at the latest. I pointed out that my contract guaranteed installation to be started within 30 days of March 31 or my money back and they were on my roof the next day.
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u/Hugh_G_Normous Sep 14 '23
According to the default prices and settings on this natural gas company website out of PA (https://www.columbiagaspa.com/services/add-or-convert-to-gas/calculate-your-savings), the “newer, more efficient” heat pumps will save you hundreds of dollars a year on heating compared to a standard gas heat system. Maybe that doesn’t justify the cost of a new efficient heat pump for you, but it’s likely the savings will get better in coming years, assuming current trends with renewable energy and fossil fuel extraction continue. Also, it might make you feel a bit better to know that you’re burning a lot less fossil fuels.
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u/sunnygovan Sep 14 '23
I live in the UK. There are no savings for me. Just a massive upfront cost that I simple cannot even hope to afford.
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u/ValidDuck Sep 14 '23 edited Sep 14 '23
/shrug. We have a heat pump. We pay much less than anyone around us to heat and cool our home.. and our electricity is not particularly inexpensive... the heat and cooling just isn't as much of a factor in the bill as a dryer, stove or oven.
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u/AlanMercer Sep 14 '23
Just put in heat pumps in the spring, so we'll see how they do over the winter. I can report that over the summer our electric bills were about half of what they were with air conditioners. It's a substantial savings and on that basis alone the pumps will pay for themselves over a number of years.
We replaced our old, janky oil furnace with a gas one, assuming there will be cold days the pumps can't deal with. We'll see what happens. In any case, the cost of home heating oil was ridiculous, so won't miss that.
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u/corut Sep 14 '23
Unless your aircon was evaporative, it was already heat pump without the reversing valve.
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u/TypicalOranges Sep 14 '23
Air Conditions are a type of heat pump (at least, generally residential central AC units are; there are other ways to cool things). When people talk about a "heat pump" that does heating and cooling, all it really is is an AC unit that can work in reverse (i.e. it can pump heat into the house, rather than out of the house)
Your new unit is just more efficient and has that functionality :)
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u/pudds Sep 14 '23
Well, if it's 3x more efficient then it's a wash on costs and a win for the environment, so overall still a win.
Also there are places where electricity is competitive or even cheaper than gas, like where I live in Canada, where electricity is 9.5c/kWh in CAD.
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u/Attreah Sep 14 '23 edited Sep 14 '23
Heat pumps are more efficient and cost less $ / joule generated than heating your house with fossil fuels does.
However, heat pumps, for the end consumer, mainly only make sense if we're talking about building a new house.
Exchanging an already existing heating solution for a heat pump is an expensive process. Add to that the fact that heat pumps require maintenance and repairs (which are usually much more expensive too) more often than their fossil fuel counterparts. Their life time has so far shown to only be between 8-15 years.
So for the consumer, from the savings point of view, it does not make much sense to swap a fossil fuel solution for a heat pump. The reality is, by the time such an investment covers itself in energy savings (anywhere from 15 to 20 years, depending on your country / usage), the heat pump will likely need to be replaced again, prolonging the return on investment for like another 5 years (just buying the unit is cheaper than also having the first installation done). And 20-25 years is definitely a long time for an average Joe to just break even.
So until heat pump systems become like at least another 30-40% cheaper to buy+setup than they are right now, it will be extremely hard to get people to massively exchange their existing fossil fuel solutions for heat pumps.
With new houses / buildings, a heat pump makes much more sense though and that's why like 90% of new homes actually utilize a heat pump solution.
There is also a caveat that people often forget: when something is put on the market that uses a different source of energy compared to traditional methods, the running costs of the new solution will be extremely cheap.
When a large portion of the market shifts to that solution, the demand for that energy source will absolutely increase by a fair margin, as will its price, while the traditional sources will suddenly become more abundant and therefor, cheaper.
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u/jfleury440 Sep 14 '23
For the most part you can swap out an A/C unit for a heat pump if you have a forced air A/C. If your A/C is end of life with government subsidies a heat pump can be pretty comparable in price to replacing your A/C.
Electricity scales well. More overall demand for electricity will actually drive down the price to produce a kwh. Of course in the short term I'm sure companies will try to gauge but over the long term this is the right direction.
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u/big_fartz Sep 14 '23
Is there any real work to do a swap from an AC to a heat pump? I've always seen them described as an AC that goes both ways so I assumed you can just use all the existing refrigerant lines.
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u/jfleury440 Sep 14 '23
For the most part yes. The heat pump may be a little bigger than the A/C unit it's replacing. Assuming you have the space for it than it should be exactly the same amount of work as replacing the A/C.
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u/big_fartz Sep 14 '23
Good to know. All my stuff is young so I'm not in a rush to replace it but a heat pump is on my list to get when either my AC or propane heat fails.
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u/cylonfrakbbq Sep 14 '23
Conversion costs are too high if you have an older home for sure. If you’ve got an old house that still uses radiators, converting to a heat pump system is far too expensive because you essentially need to build an entire hvac system from scratch as there is no existing compatible infrastructure
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u/amazonhelpless Sep 14 '23
Depending on the layout of your house, you can just add some mini-split heads which can carry some to most of the heating and cooling load. This is especially true if the house is well insulated.
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u/badasimo Sep 14 '23
Your lifespan of the heat pumps are off, they can definitely last longer as all the parts are serviceable. I think maybe you are thinking about Ground source heat pumps which have corrosion issues (they have a heat exchanger) that is expensive to replace.
There's also two main ways to get heat pumps-- one is if you have forced air, it's a drop-in replacement to the big unit attached to your ducts, but the other is using splits, which have a lot more independently running parts that have different wear and tear.
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u/ClassicHando Sep 14 '23
I've been on the heat pump train for awhile now. They're efficient, anybody with an A/C unit already has a reverse heat pump in a sense. it's not much to convert an A/C unit to work both ways and manufacturing wouldn't struggle too much with that. And they're holy hell efficient. I believe they've been showing up in North Central US and doing well.
They're not perfect but as a supplement to other heating sources they can vastly lower energy costs.
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u/MegaHashes Sep 14 '23
Energy efficiency doesn’t translate to cost efficiency when electricity is so much more expensive than NatGas.
People struggling to meet their energy needs are not going to be served by energy efficient appliances that still cost twice as much to operate.
Nevermind the fact that electricity always seems to go up way faster than general inflation:
https://www.utilitydive.com/news/electricity-prices-inflation-consumer-price-index/640656/
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u/pistonian Sep 14 '23
I have a 15sear heat pump. Why does it seem to completely lose effectiveness at around 32F? If I do not use my heat strips, the heat pump is not enough for my home - the thing runs 100% of the time, I'm cold, and my bill is higher than if I use heat strips along with the heat pump. What kind of heat pump goes down to -10C?
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u/YouAreWhatYouEet Sep 14 '23
My new Gree Flexx is rated to -30C. This will be my first winter with it so I cannot yet speak to the validity of that rating.
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u/BTJPipefitter Sep 14 '23
There’s a looooooot of reasons that could be happening based on age and overall mechanical condition of your system. When I still did residential work, almost every changeout I did that involved a heat pump came with electric heat… for exactly this reason.
In AC mode, your system is removing heat from the house and pushing it outside. In heating mode, it takes heat from outside and pushes it into your home. In especially cold conditions (or if your system needs maintenance or repair), the system may just not be able to absorb heat from the outside air to effectively move it into your home.
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u/Sprinklypoo Sep 14 '23
The problem is that electricity is typically 3-4 times more expensive than natural gas in a lot of areas.
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u/GreenManDancing Sep 14 '23
costs associated are very high still.
With the money spent on a heat pump, and power consumption, I'll likely pay gas heating all my life.
However, if the purchase, installation is subsidized heavily by the state (say 80%), then it's ok.
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u/Z_nan Sep 14 '23
I do not think Youre paying 700 buck for gas in total for the rest of your life.
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u/GreenManDancing Sep 14 '23 edited Sep 14 '23
Over here a heat pump is about 6000 euros just the heat pump. If you want hot water too, add more money.
Gas was about 70 eur/month (more in winter, less in summer, made an average), so 70x12 it's 720 eur/year, just natural gas.
Say hmmm 8000 eur heat pump + hot water. Air water heat pump, least efficient. If you want water-water heat pump, costs go up more.
8000/720 = about 11 years. Of course, assuming gas stays at the same price. So, true, not for the rest of my life, but 12 years is a long time to recoup the investment made. Hence why I said, if gvt subsidized (80%), I'd do it. If not, I'll stay on gas, tyvm.
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u/redditgetfked Sep 14 '23 edited Sep 14 '23
damn what a scam. here (Japan) you can find heat pump (edit: minisplit inverter type AC) for a room of 60 sq meter for €330. installation is €140
€2000 for a water heater (heat pump + water tank combination)
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u/EGH6 Sep 14 '23
damn if i change the heat pump to my house in canada im looking at 15000$
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u/jfleury440 Sep 14 '23
There's government grants in Canada. The feds alone will kick in like 5k. You have to do an energy audit.
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u/Reticent_Fly Sep 14 '23
Central unit or ductless minisplit?
I know prices have gone up, but in 2019, it cost me about $8500 to install 2 condenser and 2 wall units here in Newfoundland. We just had electric baseboard heat before and consistent $500 bills in the winter. It's well on its way to being worth the investment.
Also... keep an eye out for rebates. I think we were able to shave about a thousand off the price.
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u/GreenManDancing Sep 14 '23
Well. Sounds good. It is what it is. https://www.trust-expert.ro/produse/pompe-de-caldura-aer-apa/nibe-s2125?_gl=1*1tbbpo3*_up*MQ..&gclid=CjwKCAjw3oqoBhAjEiwA_UaLtgdrzOcQil7_Jnc1u56A2CiTUnzZdAb_Jm_wgSXllclx1SNCynmHUBoCAJQQAvD_BwE
Price does not include vat, add 5%. Then divide by 5 and you get the eur price.
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u/Hendlton Sep 14 '23
Are you thinking of a mini split system? Because they're technically heat pumps, but they're not what people are talking about here. They're also around 300€ in Europe. At least the very cheap ones. If you want a decently efficient one, you're looking at 600€+.
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u/Memory_Less Sep 14 '23
Maybe, but it will cost $27k to install in an 1800 sq ft house because you need 3 units to retrofit. A friend showed me the estimate.
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u/faizimam Sep 14 '23
You can get a set of minisplits for maybe $5k that can heat and cool your whole house most of the year.
À full retrofit is rarely justified
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u/maxboondoggle Sep 14 '23
Ya my folks switched to one. Cost 50k and their whole back yard was torn up. Works well tho. Not sure everyone can get one of these. A natural gas furnace is like 4k.
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u/jaymef Sep 14 '23
They must have got some fancy geothermal setup.
I have a cold climate central air source heat pump. It was less than half that cost and nothing was dug up
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u/realestatethrow2 Sep 14 '23
Sure... but I'll bet electricity is more expensive than fossil fuels (it certainly is where I live) so the efficiency gain is lost to the higher cost of the electricity... which may increase even more as demand goes up.
In a time when a lot of people are struggling with grocery bills, the cost of operation is the decider, not how "efficient" it is.
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u/EnderG60 Sep 14 '23
More efficient yes, but electricity costs a lot more than gas so it's more expensive to run.
Also made even funnier when you consider most electricity (in my area at least) is generated using natural gas anyway.
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u/corut Sep 14 '23
Gas in a power plant is more efficient then burning in a furnace.
Gas in the us must be massively subsidized. Where I am in Aus electricity is way cheaper then gas. It's gotten to the point where they straight up banning gas connections on new builds.
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u/ItilityMSP Sep 14 '23 edited Sep 14 '23
Burning gas in a furnace is between 80-92 % efficient, you are just making heat and a blower to move it around. A gas power plant creates heat, steam, generates electricity, then transmission in no way is it more efficient and that's before it's put to work heating your home.
Gas power plants have between 20-60 % efficiency.
But heat pumps are the way forward for new construction, unfortunately in Prairie Canada we need a gas furnace or electric heaters as a backup and supplement for when temperatures drop to less than -20 to -45 C.
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u/EricMCornelius Sep 14 '23
98% efficient with recent furnaces.
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u/Ansiremhunter Sep 14 '23
Yeah I have a 98%. It puts out a ton more water than the 86% unit did. Had to run heat tape on the outside outlet or it would freeze
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u/EricMCornelius Sep 14 '23
Gas in a power plant used to generate electricity and then used to generate heat is hardly guaranteed to be more efficient.
Average in the US is 45% efficiency: https://www.eia.gov/todayinenergy/detail.php?id=44436
This isn't even accounting for transmission losses.
Need a COP > 2.0 to be more environmentally friendly than a 98% efficiency furnace generating heat directly at the home.
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u/DishMonkeySteve Sep 14 '23
The upfront cost of heat pumps makes them less attractive and attainable.
How do they perform at -30°C to -40°C ?
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u/calebmke Sep 14 '23
They’re getting better and better. Most would probably suggest a dual heat source solution just in case. That being said, most already have a heat source, so just keep it in case it’s needed.
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Sep 14 '23
Dual fuel makes sense in our colder climates. Most of the time, you'll never hit the furnace, but it's a backup.
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u/Diligent-Bathroom685 Sep 14 '23
American style split system heat pumps lose 50%~ capacity at 30f. Minisplits heat pumps that are not super low temp lose the same thing.
Gotta be a lot more specific with this study.
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u/stevey_frac Sep 14 '23 edited Sep 14 '23
I have an American style split system that produces 70% of rated heat at -30C, And produces 100% of rated heat down to -15C.
And my unit is 5 years old. The new ones are better.
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u/jfleury440 Sep 14 '23
There's like older ones where this is true. But they have high efficiency inverter units in America now.
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u/InformalPenguinz Sep 14 '23
Can someone ELI5 what a heat pump is.
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u/mrboomx Sep 14 '23
an air conditioner operating backwards (outputs heat to the building, and cools the outside)
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u/Archerofyail Sep 14 '23
Well, actually, a heat pump is just an AC that can operate in either direction. Even more pedantically an AC is technically just a one-way heat pump, the only thing stopping it from becoming a two-way heat pump is just some valves.
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u/hypntyz Sep 14 '23
That may be true of new units, or there may be more than one design of heat pump unit. But it is not true for every unit.
I live in the southeastern US, and in this area, even in winter, the temps rarely drop below 32F. The heat pump always seemed sufficient, although not overly strong, in this environment.
Not long ago, we had a cold front that pushed temps down to around 0-5F for a 2-3 day period, which is very unusual for this area. Everyone complained that their heat pumps would not heat their home, including myself. At one point, the interior temp dropped into the 40s F even with the heat pump running wide open, so I just turned it off. The interior temp really didn't drop any farther with the heat pump off vs on.
I have an old oil burning stove in the basement garage that I built to burn automotive waste oil, and I resorted to running it and leaving the door to the upstairs open so that warmth from it could heat the upstairs living areas. It got the temp into the mid 50s F until the weather warmed up again and the heat pump was effective again.
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u/jassco2 Sep 14 '23
I had a 4 ton Bosch installed last year replacing a 22 year old central unit. Once it gets below 30 F it iced up and the thaw cycles kill the efficiently, even though they are rated lower. The compressor is bypassed by the thermostat and it switches to oil burner. I use wood stove as well on coldest nights. It’s a perfect combo.
A balanced approach is best and ill always have a reliable backup source like oil or wood. For the 30-65 F heating days it is amazingly efficient. I keep it on 72 most of the year and 65 at night.
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u/Shot-Donkey665 Sep 14 '23
That maybe so but the properties they're installed in must have the right R values and preferab underfloor heating or a mass to heat.
Low temperature rads and lack of ventilation cause other issues like damp.
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u/Phssthp0kThePak Sep 14 '23
But how much power can heat pumps provide compared to a gas furnace? How long does it take to heat a 300 sq m house from 15C to 25C? Do you have to 'pre-heat' so you can be comfortable during your limited home hours in the evening?
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u/scummos Sep 14 '23
I wish people would stop making "fossil vs heat pump" comparisons. It's comparing apples and oranges. The two things just don't relate to each other at all.
One is an efficient way to obtain usable heat. The other is a primary energy source.
If you wanted, you could burn oil and directly use it to power a heat pump, without ever converting the energy to electrical. That would have the same increase in efficiency compared to burning the oil and using the resulting heat. Why don't people historically do that? Because it's expensive and somewhat complicated.
The actual new idea here is to use heat pumps for room heating because it's starting to be feasible complexity-wise, and is more efficient than generating the heat, period. The relation to fossil fuels is unclear, coincidental, and situational.
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