23 ms·

Do heat pumps work in cold climates?

• sampo 4y ago
  > modern cold-climate heat pumps can heat a home efficiently even when the temperature drops below -10 degrees. -10F is -23C. Edit: I first put "-10 f to c" to google, and google converted it to "10 fahrenheit is -12 celcius".
  • shapefrog 4y ago
    -10F is -23.33C
    • Ndymium 4y ago
      OP must have accidentally put in 10°F, which is -12°C.
    • hackeraccount 4y ago
      Also 249.817 K
      • shapefrog 4y ago
        Also f'ing freezing.
      • adrian_b 4y ago
        As an electronics engineer, I always prefer millivolt to kelvin, so 21.528 mV instead of 249.817 K. Special units for temperature are no more useful than yards or pints.
        • _Microft 4y ago
          The unit here should be meV/k_B instead of mV btw (the latter is proportional to the temperature but doesn't have the unit of a temperature).
          • adrian_b 4y ago
            The convention used by SI to give the name "kelvin" to the unit of temperature and to set its value by giving a certain value to the Boltzmann constant is completely artificial and its only justification is to ensure continuity with a certain historical tradition. A completely equivalent convention would be to give the name "volt" to the unit of temperature and to set its value by giving another value to the Boltzmann constant, numerically equal to what is currently named as the ratio between the Boltzmann constant and the elementary charge. The fact that "volt" is also the name of the unit of electrical voltage does not matter. The name of an unit does not identify the physical quantity measured with it. For each SI unit, there may be many distinct physical quantities that may be measured with it. (This is a very desirable feature of the system, which avoids the proliferation of many arbitrary universal constants in the formulas.) This is actually a fallacy not infrequent at computer programmers, to believe that storing the measurement unit together with a number is enough to unambiguously determine its meaning. In reality, also the measured physical quantity must be known. In many cases the intended physical quantities can be deduced from the context, but there are cases when you have old tables or graphs whose meaning is hard to guess, even when having the measurement units. The unit eV (electron-volt, used for energy) does not belong to the SI, even if its use along SI units is officially tolerated. The same is with the volt as a temperature unit. Like the Fahrenheit degree, it is not an SI unit, but it is possible to use a system of units that differs from SI only by measuring the temperatures in volt. Such an SI alternative has two advantages over SI. One is that in many frequently used formulas a multiplication with an universal constant can be omitted. The second is that it is much easier to have an intuitive understanding of the effects of various temperatures when comparing their magnitudes in volts with the values of some voltages or of some energies expressed in eV. Moreover, the use of the kelvin is not well justified by backward compatibility, because few people are accustomed to think about temperatures expressed in kelvin. Replacing the Fahrenheit degree with the kelvin brings a computational simplification, but if that is the target, going directly to the volt achieves more.
        • PaulDavisThe1st 4y ago
          But yards or pints are really useful units!
          • adrian_b 4y ago
            Like also the Celsius and Fahrenheit degrees, all such traditional units can be useful, but only as long as their use does not involve computations more complex than comparisons, subtractions and additions.
• rayiner 4y ago
  > Contrary to popular belief, modern cold-climate heat pumps can heat a home efficiently even when the temperature drops below -10 degrees. At this temperature the best cold climate heat pumps are still more energy efficient than furnaces and boilers This is maybe true if your house is insulated to Scandinavian standards. Our heat pumps here in Maryland get iffy around 20 degrees in our circa 2005 house. We have a nice oil burner heating a hydronic system that does a great job at that point.
  • throw0101c 4y ago
    > We have a nice oil burner heating a hydronic system that does a great job at that point. A primarily for hydronic heating unit that goes down to -20F / -29C: * https://www.spacepak.com/solstice-inverter-extreme https://www.spacepak.com/solstice-inverter-extreme
  • Ndymium 4y ago
    Having a heat pump transfer the energy to heating water that is then circulated in radiators is becoming quite common in the Nordics, and often used as a replacement for an oil burner. It's more efficient than a regular heat pump that just uses hot air to warm the home. Of course dealing with crappy insulation can often be more bang for buck.
  • KarlKemp 4y ago
    If you believe lack of insulation is the problem, the heat pump is just underpowered. A more suitable model or, even better, adequate insulation, would likely be a triple win financially, environmentally, and for your and your neighbors' health.
• causi 4y ago
  I don't understand why anyone would be worried their heat pump isn't going to work in winter. I've never seen a heat pump installation that didn't include an emergency resistive heater.
  • SigmundA 4y ago
    It's not so much a worry as an efficiency thing. If your in a cold climate that needs resistive heat its a lot less efficient to burn natural gas at power plant at 50-60% then turn to heat with a resistor in your house, than to burn it in your house at 80-90% efficiency. Thing about a heat pump is it basically turns into a resistive heater once it can't capture any outside heat, then you just have heat of compression. This changes with a lot of renewable and nuclear power, but also heat pumps that can keep operate rating above unity in those cold temps really start making sense.
  • bigdog90 4y ago
    In my house we only have electric heat available. When it gets too cold, the heat pump no longer keeps up and the resistive heater in the furnace turns on. It is more expensive to use the coils than the heat pump. It is important to understand the environment it is running in to accurately predict your energy costs. The previous owner should have installed one that could run in colder temperatures.
  • cwingrav 4y ago
    Mine cuts off at 35F and I have to manually switch on the oil. I live where winter is normally below 35 at night. Very annoying system. (I didn’t pick it)
  • melolife 4y ago
    So there are two problems as I see it: Firstly you see analyses like these where the author goes "see, heat pumps work fine in cold climates, look at these success stories!", and then proceeds to list a bunch of places that aren't particularly cold. People think Norway is cold, but if you look at Wikipedia then the average daily low for Tromso (a random northerly Norgewian municipality) in January is -5.6C, with a record low of -18C. Compare this with Calgary, a relatively southerly prairie city with an average low of -13.2C and a record low of -44C. The second problem is that they say "don't worry, if it actually gets cold it switches to resistive heat!" The problem here is that the extremes absolutely matter, because this is when demand is highest. If a prairie province/state switches everyone to heat pumps, then your grid had better actually be designed for everyone to be using resistive heat for weeks at a time, because that's exactly what's going to happen when you need it most.
• donatj 4y ago
  The lack of scale on temperatures throughout is remarkably frustrating. I am assuming Fahrenheit as the graphs indicate this but the content really should as well.
  • mnw21cam 4y ago
    Yeah, I hate this. The title (with the words "cold climate"), the numbers (below 20 degrees) and then talking about Finland (where degrees are definitely Centigrade) just creates too much cognitive dissonance. If you're writing an article about temperatures, and you want to use Fahrenheit, please actually say so, otherwise you'll have all your readers from 90% of the world's population looking at you oddly.
• throw0101c 4y ago
  Down to -20C, and even -25C: * https://www.mitsubishielectric.ca/en/hvac/professionals/fs-series https://www.mitsubishielectric.ca/en/hvac/professionals/fs-s... More advanced unit (primarily for hydronic heating) that goes down to -20F / -29C: * https://www.spacepak.com/solstice-inverter-extreme https://www.spacepak.com/solstice-inverter-extreme
  • onphonenow 4y ago
    The lie / part skipped is while they “work” to those temps, they don’t work well.
    • iso1631 4y ago
      If you get to -20C a couple of times a year but normally it's -5, it doesn't matter that it's inefficient for 2 or 3 days a year, as it's very efficient for 360 days a year
      • irishsultan 4y ago
        It doesn't matter for you personally, but it kind of matters globally. If everyone hits that same inefficiency at the same time then there needs to be a lot of extra capacity in the electric grid that can be spun up during a small part of the year.
        • dublinben 4y ago
          There's already plenty of spare capacity in winter time that is necessary to support peak demand in summer time. Loads like electric heat pumps are also perfect candidates for automated management to smooth out load spikes, so there would be no "at the same time" to worry about. https://learn.pjm.com/three-priorities/keeping-the-lights-on/how-energy-use-varies.aspx https://learn.pjm.com/three-priorities/keeping-the-lights-on...
          • SketchySeaBeast 4y ago
• SigmundA 4y ago
  Need to check my math but a heat pump that can do a COP of at least 2 powered by a 60% efficiency natural gas power plant should be more efficient than a 90% efficient natural gas furnace. That's not even counting a renewable/nuclear mix on the grid or say solar on your house. Air source heat pumps are technically solar, they take heat from the outside air which was warmed by the sun. Even better would be geothermal ground source heat pumps but the install costs and complexity are much more. Electrification has so many advantages since your decoupling and abstracting power source from use, now your car or your house heating is not tied to a specific fuel.
  • someguydave 4y ago
    In my area natural gas is 3x cheaper than electricity per kwh, so you might be right that the electric solution you outlined uses less overall energy but the end user will be punished with a higher overall utility bill. Also, in cold climates where gas heat is typical the overall energy needed to heat the house is very large compared to typical winter electric use, which will likely anger homeowners after heat pump installation.
    • SigmundA 4y ago
      In my area it's about 2.6x so a heat pump only needs to have a COP of about 2.4 to equal the cost of natural gas per unit of heat delivered when compared to a 90% efficient gas furnace. These modern air source low temp heat pump can maintain a 2.4 COP down to about 17F. Note my area is pretty warm (FL) so even though I have natural gas to the house for cooking and hot water I do not use for that as my air heat pump works very efficiently in the cool temps here. I have resistive heat as a backup and it never turns on. Geothermal heat pumps can maintain 3-4 COP year round in any temp then your easily surpassing natural gas even at 3x the cost.
• akokanka 4y ago
  Source live in cold country. Heat pumps work lovely till -5 to -10. Then most folks start using extra heating.
  • dx034 4y ago
    F or C?
    • timbit42 4y ago
      Probably F. New heat pumps are usually good to -20C or -25C, which matches -5F to -10F. My heat pump is 11 years old and is good to -15C.
• sokoloff 4y ago
  I recently replaced a (very) old gas boiler with a new gas boiler after trying and failing to make an air-to-water heat pump make economic sense. (It 100% would have worked technically/thermodynamically.) It was going to be a bit over $20K more, which at only 4% opportunity cost of that money (low, IMO), means that an $800 savings per year would literally never pay back, let alone within a 20-year projected service life. I’ll re-evaluate 15-20 years from now when it’s time to change again. (Eastern MA)
  • ilyt 4y ago
    At current or predicted future electricity/gas prices ? I can imagine having solar and using partly that (instead of selling it back to grid for pennies) might've skewed that too
    • sokoloff 4y ago
      Our grid is plurality natural gas fired, so I’d expect them to broadly track for the majority of the lifecycle of this equipment. A slate roof precludes advisable/economic solar installation, plus the major part of heating load is in winter (obviously) and in the 75% of the day that’s not 9AM to 3PM.
      • Jochim 4y ago
        As a fellow owner of a slate roof I recently came across panels made to look like blocks of slate tile[0]. They look to be a bit less efficient than a traditional panel and I've not looked into the costs yet but it's nice to have the option! I imagine there would be similar products in your neck of the woods. [0] https://www.gb-sol.co.uk/files/PV%20Slate%20brochure%20v2_3.pdf https://www.gb-sol.co.uk/files/PV%20Slate%20brochure%20v2_3....
        • sokoloff 4y ago
          Those are beautiful; thanks for the reference! At the price of labor in New England, I kind of doubt those will have an economic payback either, but I'll do a little more poking around.
• joaodlf 4y ago
  > The load also depends on unique characteristics of the home like the amount of insulation or the type of windows and doors. A home built in 1850 with no insulation requires more energy than a brand new home. The load is just a technical way to describe and measure all of this. No kidding. The site is all about switching from carbon, which I am all for, as would anyone that cares even slightly about the planet. BUT. If you do live in a 1850s house with no insulation, getting a heat pump is a colossal waste of money that will not do the job. No matter how many fancy biased graphs and numbers someone comes up with. Any responsible heat pump installer will firstly look at your home to determine if a heat pump is remotely feasible. Unfortunately, in the UK, only very recent new builds can comfortably accommodate a heat pump. That or older properties that have had CONSIDERABLE insulation work done to them (and I am talking the expensive kind like internal/external wall work, not just the easy jobs like loft insulation). Be very careful with heat pump cowboys, if you are getting quotes that don't include a site inspection, run.
  • russdill 4y ago
    As long as the heat pump was properly sized for such an uninsulated home it would still heat it more efficiently than a resistive element heater and just as completely. Of course, if saving money is what you want to do, then yes, insulate before throwing dollars at anything else.
    • joaodlf 4y ago
      The costs are totally prohibitive, though. We're talking tens of thousands of pounds, whatever direction you decide to take. You could spend 10s of thousands of pounds in a "properly sized" heat pump system. Or you could spend 10s of thousands of pounds in insulating your home + a more moderate heat pump.
      • ClumsyPilot 4y ago
        Insulation always pays for itself in the long run, but the period of payoff like peruod of payoff on a mortgage - 10-20 years. We need very generous finance on making home improvements
• onphonenow 4y ago
  Some cautions - noticeably lower heat output at cold temps. - install is important, many installs done get adequate ventilation- so cold air collects near unit. - high ceilings can be an issue, evaluate fans to bring heat down - gas is amazing for heating in radiant heat. We really like our radiant heat experience- global warmth and good volume - I’m not sure if tech term, but heat volume can be an issue. We are in a 100+ year old house. The heat pump in very cold weather seems able to generate heat, but no where near quantity that gas system did if you just cranked it - we are getting hit with tier three electric rates - switched dryer to electric etc - costs get tough!
  • tootie 4y ago
    Also this whole conversation is specifically about air source pumps. Geothermal are immune to air temperature fluctuations with the tradeoff being higher installation cost.
• Tor3 4y ago
  The heat pump I have installed reaches 1:1 at -20C, i.e. at that point there's no gain. But a) it rarely gets that cold around here, and at -10C it works fine - there was a dramatic (seriously dramatic) drop in amount of electricity I used during winter compared to before installation, and b) My heat pump was installed in 2010, since then they've only got more efficient and 1:1 is somewhere around -30C (or was, a couple of years ago when I last checked). And what it does when it's really cold _and_ somewhat humid outside is that it detects when frost appear on the outside element, at that point it reverses the flow and uses the heat from inside to defrost the outside element. As far as I know it does not include any actual resistive heater for this (though I won't bet my life on that statement). It's been working very reliably all these years (except for a leak in the cooling fluid which appeared relatively soon after installation, promptly fixed by the provider). I have to get it cleaned now and then to keep up the efficiency. It's in every other respect completely without hassle. EditAdd: The Japanese heat pumps sold in the coldest areas are "Nordic" models. They are extremely efficient. But in Japan, where they're made, you can't get them. Or at least, we could only find less efficient models. But I haven't been to Hokkaido yet, I'll have a look in the stores there to see if they have them there.
  • HPsquared 4y ago
    Is that "no gain" in terms of energy (i.e. heat energy out = electricity in), or financial (i.e. cost of electricity consumed by heat pump = cost of equivalent gas-fired system)? EDIT: or is it "well-to-wheels" style energy (i.e. primary energy consumed by heat pump = primary energy consumed by gas boiler), or is it CO2 (same emissions)
    • iso1631 4y ago
      With a 1:1 ratio it's heat energy out = electricity in, minus a small amount of efficiency loss (any heat produced on an external heater) As to cost wise it depends on the cost per kWh of your electricity vs gas. In the UK gas is far cheaper per kWh. CO2 wise it depends on the CO2 intensity of your electric source vs a local gas burner. However that only applies when it's -20C. When it's a more reasonable like now at 7AM in Chicago when it's 2 degrees C, you're generating something like 2.5kWh of heat for every 1kWh of electricity. That may not be financially beneficial if your gas is 5c/kWh and electricity is 30c/kWh, that depends on your various deals. For me in the UK, my external oil boiler this winter has cost about 10p/kWh. My electricity is 21p/kWh. A heat pump I looked at was a 3.84 ratio, so if that ratio held down as far as typical winter temperatures of 6C (it's currently 11C), that would be 5.5p/kWh, and obviously far less CO2 per unit of heat.
• theropost 4y ago
  It's -22C here this morning (-8f), and both of my heat pumps are working fine (currently 20.5C indoors). I have an LG, and a Fujitsu. The LG has an element inside the central air-handler as well, so if it gets too cold, you can switch that on to provide backup heat. I expected to need it last night, but the heat pump did fine without it.
• avidphantasm 4y ago
  Our house (in Northern New England) has heat pumps (which we added in the last two years), a wood stove, and hydronic baseboards powered by an oil-fired boiler (which we now use as backup). The heat pumps so far are able to heat just fine, and are great for maintaining temperature while we aren’t at home. However, we much prefer the comfort provided by radiant heat: wood stove and baseboards. Once the boiler needs replacing, we will likely switch to a wood pellet boiler so that we can use the radiant heat more when it starts to get colder/before the wood stove had heated up in the morning/when we get home in the evenings.
  • amluto 4y ago
    You can get air-to-water heat pumps (e.g. Chiltrix), and some manufacturers have refrigerant-to-water accessories for conventional systems. So you could have a heat pump heat your floors.
    • avidphantasm 4y ago
      Thanks for the pointer. I’ll look into Chiltrix. However, based on my state’s tracking of heating fuel prices, wood pellet is by far the cheapest [1] and is a local/regional resource. [1] https://www.energy.nh.gov/energy-information/nh-fuel-prices https://www.energy.nh.gov/energy-information/nh-fuel-prices
  • DFHippie 4y ago
    We're in Vermont in a house built in 1926. We blew insulation into the walls, insulated the attic well, and replaced the ground floor windows (some day we'll do the rest of the windows; in the meantime we use plastic film in the winter). We heat with pellets primarily, but when the pellet stove starts to struggle we turn on the heat pump we installed a few years ago. It warms up the house in no time.
  • Tor3 4y ago
    I actually prefer the heat pump over radiant heat. My heat pump is placed low on the wall, about a meter or a bit less above the floor, in one side of the living room. Due to the air it's pumping out I get an even nice temperature everywhere, while if I use the wood stove with the heat pump switched off it gets very hot near the stove while it's cold in the other section (around the corner) of the living room, not to mention the kitchen. In practice I end up pouring in wood fuel and let the thing burn to maybe 10kW just to get the warm air seeping into the kitchen, eventually, and then it's too hot elsewhere. I realize I could set up fans etc, but really - it's so much nicer to use the heat pump and get a uniform heat distribution.
• earlyriser 4y ago
  They work pretty well, I live in the 2 hours north of Quebec City and it works most of the winter. Today is the first day that I turn it off as it's -22C outside, but as soon as it's -19C it could work again.
• RobinL 4y ago
  I'm a air-to-air heat pump owner and I love it and think they will be a key part of climate mitigation. However, from a climate change policy perspective, it is important to _emphasise_ that heat pumps are less efficient at lower temperatures (lower COP) and not try and pass this off as a myth. (I recognise this article is presenting the 'myth' as operating at a COP of < 1, but many people will misinterpret that) To put this in perspective in the UK, in mild weather demand is something like: - about 40GW total electricity demand - about 100GW of gas In mild weather, my heat pump gets a COP between about 3 and 4. Which means that, if we want to replace gas usage with heat pumps, we need a further 25-33GW of electricity to power the heat pumps. This is eminently achievable. See here https://twitter.com/heatpolicyrich/status/1612385243251572738 https://twitter.com/heatpolicyrich/status/161238524325157273... and the latest edition of the economist quotes there being 260GW of wind projects in the pipeline for the North Sea (amongst 9 countries): https://www.economist.com/leaders/2023/01/05/why-the-gusty-north-sea-could-give-europe-an-industrial-edge https://www.economist.com/leaders/2023/01/05/why-the-gusty-n... In extreme cold snaps, total gas demand doubles to about 200GW, and electricity goes up to maybe 60GW. The problem is that now the heat pumps are getting a COP of maybe 2, if you're lucky. So now in the UK we need 100GW of electricity to replace gas, which is a big ask even when the wind's blowing. At the moment, wind output peaks at about 21GW, though records are being broken all the time. None of this is to say we shouldn't switch to heat pumps where possible. Mine was cheap to install (£1,895+vat) and has halved my gas usage. Must be one of the most cost effective way of mitigating the current gas crisis (after reducing usage!). I think it's just worth understanding some of the important numbers.
  • nickspicer1993 4y ago
    Also worth adding that in the UK new homes will not allowed to be built with boilers by 2025 and they will need to be slowly phased out in next decades so definitely invest in home insulation and a heat pump if your boiler is on the way out!
    • RobinL 4y ago
      Yes - good point. That touches on another myth I've heard frequently - that heat pumps are only suitable on well insulated homes. I think this may be true in relation to some air-to-water systems (?), but it ignores the possibility of just installing a cheap air-to-air system on top of existing heating (either gas or air-to-water). Air to air systems are really well suited to homes with a combined kitchen/living room which is the main room in use most of the day. We only heat the kitchen/living room during the day (our main living space), and the heat pump is more than adequate for this. It typically uses around 10kwh a day for quite a big, not very well insulated room.
• dahfizz 4y ago
  I have a heat pump in New England, and it works but damn is it expensive right now. I think I need to upgrade to a bigger pump. My aux heat is kicking on semi regularly, and the heat pump is running it's reverse cycle pretty regularly. I think heat pumps are an absolute no brainier. They work great for AC during the summer, and they heat my house really cheaply in the fall. I'm disappointed in my pumps winter performance, though.
• gbil 4y ago
  I don't like the article because it starts with a question that answers through a lot of jumps trying to essentially sell you the specific solution. Probably that is how they write articles in general from a couple others that I've seen but it would have been more fair to just answer the question in a simple way, yes because here are the specs sheets showing that Expanding a bit more on my comment, the factor in sell stats from Scandinavia where home insulation is on another level and especially in Norway they just move away from fossil fuels in general - while they sell them elsewhere - regardless if for example EV batteries keep half the charge in winter time, just because they have money. Then the factor of house insulation in general, sure a much better insulated house can do with a not very efficient solution. And while they only touch a bit that every case is different, they don't discuss all the factors just the ones that can elevate the heat pump case. Doesn't it matter if this is a new installation with fan coils for example or a heating replacement case ? Electricity costs also, or this is a US specific sale ? and etc. etc.
• snvzz 4y ago
  What pisses me off about this article is how it keeps talking about "degrees" and about Europe, but then you find out it's F degrees and not C degrees if you look at the graphs. Please use SI units, but in any event, please place units next to numbers!
  • bontoJR 4y ago
    Very confusing indeed.
  • deleted 4y ago
    [deleted]
  • RodGodKiller 4y ago
    Minor thing: Celsius isn’t SI either.
    • iso1631 4y ago
      Degrees Centigrade is an SI derived unit, just like Joule and Watt https://en.wikipedia.org/wiki/SI_derived_unit https://en.wikipedia.org/wiki/SI_derived_unit
  • HPsquared 4y ago
    They also don't give units for the price of natural gas.
• Myrmornis 4y ago
  Does anyone have experience choosing/installing/using a heat pump for both cooling and heating? The weather at our house gets just below freezing in winter and very hot (38C/100F) in summer. Currently, heating is via wood burner, solar thermal, and random space heaters, and we don't yet have a cooling solution. House has thick stone walls and a tiled roof (southern Europe).
  • Tade0 4y ago
    Check out ground source heat pumps. A one sentence summary of them is that they use the thermal mass of the ground to provide you the annual average temperature.
  • deleted 4y ago
    [deleted]
  • elmolino89 4y ago
    We have such a thing (some Mitsubishi model I will check later on if needed\) at home in Catalonia. Works OK, but the house despite being well isolated in general has a weak spot: dark external blinds. Without some external shading these warm up in no time, so the air between blinds and windows goes probably +45C or more. To combat this the heat pump in the air condition mode has to work way harder. So a bit like with a Victorian house in winter where isolation is the key: one has to start with making sure that the house interior gets as little heat from sun in the summer as possible.
    • Myrmornis 4y ago
      Thanks! Sure if you get a chance I'd be interested to know your model and when you got it. (We're in Portugal - Alentejo).
• jtode 4y ago
  The writer is insultingly bad. In the first paragraph, they talk about temperatures dropping below -20, then immediately pivot to talking about -10. A pump that works below -20 would be extremely interesting, IF the article was about that. It's not. It's standard heat pump salesbabble with catchy opening line, which happens to be 100% deceptive about what will follow. It's so obvious and hackneyed, I want to sit the writer down and discuss their life choices with them.
  • PaulDavisThe1st 4y ago
    > A pump that works below -20 would be extremely interesting, Like this one? https://www.mitsubishielectric.ca/en/hvac/professionals/fs-series https://www.mitsubishielectric.ca/en/hvac/professionals/fs-s...
• tjansen 4y ago
  My understanding is that modern heat pump installations for colder climates come with an electric heat strip, a conventional heating element. It will take over when the heat pump can't work efficiently anymore. So the heat pump will continue to work. It won't be more efficient than a conventional heating element though - at the time of year when most energy is consumed. So heat pumps will lower overall energy usage, but not peak usage. https://carolinacomfortsc.com/hvac/what-are-heat-strips/ https://carolinacomfortsc.com/hvac/what-are-heat-strips/
  • kenmacd 4y ago
    While they can have these elements, heat-pumps in general have come a long way in their ability to get heat out of the air at cold temperatures. Mine is still over 160% efficient at -13F, with no loss of capacity. Below that it'll still operate at over 100% efficiency, but capacity starts to drop, so some part of the heating load may need to be made up by other means (it's common to install a handful of cheap resistive heaters for that case, as they add a redundant system that can continue to work even if the heat pump is out of service). > So heat pumps will lower overall energy usage, but not peak usage. This would only be true if we go far beyond normal 'cold climate' temperatures for a long period of time.
• londons_explore 4y ago
  This[1] diagram from the article is really the crux of why many homeowners skip the heat pump option when fitting out a home. Notice how the promised specs, a COP of 3 at 17F outdoor and rated power, aren't achieved by a single real user? The real users get between 1.0 and 2.3 COP. That means the cost of your system will be approximately double to run what the manufacturers specifications claim. The government needs to step in and force companies to measure their heat pump systems in conditions more representative of a typical installation. [1]: https://lh5.googleusercontent.com/05uL7FR8oHB3leKUvLABRMZTJ4FGwjq8yvDPGZVjauhnwXcEjQC3Aesfqs85CHkYnQXmiURLDCNsyLfF2STeqBDqMXye1YNMhos0XM7-alwYcoBl1cEIhb3CyefIXESdF-NteBPZ https://lh5.googleusercontent.com/05uL7FR8oHB3leKUvLABRMZTJ4...
  • orra 4y ago
    > That means the cost of your system will be approximately double to run what the manufacturers specifications claim. Wait, seriously? That's (a) disappointing, because I thought heat pumps were pretty great. And (b) you're absolutely right: it's misleading advertising.
    • londons_explore 4y ago
      Typically these systems underperform because they are tested in ideal lab conditions, but then the actual installation has lots of non-idealities (long pipes with lots of bends, dirt, dumb thermostats, wrong flow rates, poor airflow, blocked filters, things cycling on and off, etc). The full report that the (uncited!) diagram is from is here: https://acep.uaf.edu/media/290488/Air_Source_Heat_Pump_Potential_Alaska.pdf https://acep.uaf.edu/media/290488/Air_Source_Heat_Pump_Poten... The report describes a few other heat pump models which do meet the advertised specs.
      • orra 4y ago
        Thanks, that's reassuring.
      • silverlake 4y ago
        Thanks for the link! I have Fujitsu which I run when outside air is above 40F. Looks like it gets an amazing COP of 5 to 6, far exceeding the spec. I have tankless hydronic heating using natural gas for most of the winter, but it couldn’t quite heat my house when temps dropped to 5F.
• behohippy 4y ago
  My dad builds houses in northern Ontario and heat pumps seem to be getting more popular on new builds. This is a place that regularly gets below -30C in the winter. The heat pump (usually a heat pump/AC combo unit) by itself doesn't work in these conditions, you'll always pair it up with another system like a natural gas furnace, or resistive heat electric. My personal heat pump is an older unit, it works down to -10C then then forced air electric (resistive) furnace kicks in. That thing is pricey to run, so I also light up the wood stove at that temp to reduce the costs.
  • timbit42 4y ago
    Would the resistive furnace would be about the same cost as running electric baseboard heaters?
• icecap12 4y ago
  Over the last 10 years we've had to replace our furnace twice, and happen to have both gas and a heat pump (a hybrid system). Each time, we had a different contractor do the installation...but both guys told us that they like to run gas below like 30 degrees. The second guy said he runs gas exclusively - no heat pump installed in his home. I asked what the primary differences were in terms of efficiency, and both claimed that temperature at the register is significantly hotter, producing more heat with less effort and therefore more efficiency. I haven't done any scientific testing; the only data I have to measure the difference is my energy bill (which of course is subject to rate changes). But I have indeed observed that with gas, our bill is lower during the very cold months, and I'm able to see this because I have years of data on what we spend each month on energy.
  • dahfizz 4y ago
    I have a aux heater that kicks in when the heat pump can't keep up, and I have noticed this. When the heat pump is running, the air coming out of the vents is barely warmer than ambient. Definitely less than 70F. When the aux heater kicks in, the air is actually hot. A side effect is that the heat pump needs to run a lot, because heating a house to 62F takes a long time with air that it 65F.
• 1ncorrect 4y ago
  I’ve been wondering for a while now if it would be worth coupling a heat pump coils to the heat sinks of a battery, inverter or other building electronics to help offset the diminishing returns at the lower extremes. The simplest example would be a heat pump with its own built in UPS style battery, but I also see it being built with coupling to a power wall style house battery.
  • blitzar 4y ago
    In summer yes, but efficiency is not a problem then. In winter those are providing ambient heat within your property anyway.
    • 1ncorrect 4y ago
      This equipment would be installed outside, the difference being to position it near, or coupled to, the compression loop of the heat pump. When the pump is running, it draws from the battery, which will need to dissipate heat through its operation. Why not capture that heat and redirect it where desired. In summer, you could decouple it and use standard separate heat dissipation mechanisms.
      • blitzar 4y ago
        A black body catching some rays would give a decent boost (for part of the day at least) - https://www.youtube.com/watch?v=FtfaZMahSUU https://www.youtube.com/watch?v=FtfaZMahSUU - just putting the split unit somewhere that catches the sunshine would probably be a non negligible positive! Once we go down the heat extraction / transfer path some interesting efficiencies should crop up - any waste heat (higher than ambient temperature) exiting a property could reasonably be captured and used.
• HPsquared 4y ago
  Quite sneaky how the article gives the price of electricity in cents per kWh, then some un-named unit for the price of natural gas (which is very cheap in the USA). The price per kWh is much less than the price of electricity.
• VLM 4y ago
  From a technical engineering perspective the -22F claim in the article is amazing. When I was a kid that number was +40F and we walked up hill both ways to school in the snow. As cool it is as an engineering story, its AWFUL as a marketing article. Heat pumps have the same problem as EVs, its been pounded into the general public for decades that some number isn't enough for some people and the number improves every year, every decade. So the "general public" shitpost on the internet around the turn of the century that an EV that only goes 100 miles is useless and once someone sells an EV that runs more than 100 miles the entire world will convert en masse. Non marketing people do NOT understand that it doesn't matter that people only need 0.1X or 0.5X or whatever if you market a continuously improving number they'll ALWAYS demand they are not buying until that number improves to 1.25X or 1.5X. And as technology improves, we get there in a decade or two, but it'll be the same reluctance. I absolutely guarantee that 90% of the people on the internet will be disappointed in EVs in 2030 because range will only be 750 miles and if only someone would sell an EV with a range of 1250 miles THEN they'd buy it. It doesn't matter how many well intentioned people point out that the average driver only goes 30 miles a day or whatever. You don't fix a marketing problem by screaming math equations at people. Not most people. Actually works with engineers, sometimes LOL. You sell EVs buy demonstrating they plug in anywhere in ten seconds vs some poor bastard walking uphill thru a blizzard carrying a heavy gas can because he ran out of gas. The other marketing problem with heat pumps is handled horribly by the article. Everyone knows they work like shit when its cold. Exactly when you want to be the toastiest they don't work. Its like marketing a spare tire for a car guaranteed to be flat when you need it the most. You can't gaslight people into wanting to be cold during a winter storm. The solution to this marketing problem is obvious. Instead of bitching at people that they would be holier than thou if they enjoyed being cold in the winter after spending a huge amount of money to avoid being cold, market (not sell) a heat pump model that has a 100KW electric space heater that requires special permission from the electric company to connect and flood video commercials of people in the arctic circle turning their houses into saunas by turning up the thermostat during a blizzard and they're all in towels and sweating while snow blows by the window. Everyone who actually lives up north knows its warm when it snows and cold when its not snowing but most of the people selecting a furnace for their house in Florida don't understand or care but they don't want to feel cold when its cold outside so they don't buy heat pumps, at least not now. After the new meme sets in that heat pumps turn your house into a sauna, don't buy a heat pump unless you want to sweat in the winter, the regular general public will start buying heat pumps. "Well I don't want all the hassle of installing the 100KW one, I'll buy a cheaper appropriately sized on instead"
• elmolino89 4y ago
  Air heat pumps obviously are way less effective when the temps outside are negative. The ground heat pumps work better, but the installation costs are the barrier. The silly thing is that even on a sunny winter day an air pump uses a fairly cold air instead of some heated by the sun collector. From what I got such air & sun collector systems are complex to manufacture and maintain, so the more energy hungry air heat pumps dominate.
  • timbit42 4y ago
    Here is a plan for solar air heater panels that is quite efficient: http://www.iedu.com/Solar/Panels/index.html http://www.iedu.com/Solar/Panels/index.html
• KaiserPro 4y ago
  I think the single biggest mistake is differentiating HVAC from heatpumps. The second is not insulating In the UK most newer offices use aircon to provide both heating and cooling. Its cheaper to put in, requires less maintenance and regulatory oversight. However the biggest issue is that for any of your heating/cooling systems to work cheaply, you need insulation, and enough of it to do what you need. That means insulating floors, ceilings and walls. Moreover, having a bunch of thermal mass makes stuff a lot more comfortable. My house is a 1930s semi-detached house. Think harry potter, english suburbia, and you'll get a good idea. It was designed to have an open fire in each room. This means that it has an airbrick in each room, plus a suspended wooden floor, supplied with, you guessed it, a fucktonne of air bricks. This means in its natural state, its windier than an open barn. This means that with a 30kw boiler (8.4 tons or 100K BTU) working flat out for hours could get the house to about 19c (~66f) at best. Not only that but condensation clung to the walls, meaning a fucktonne of mould. Combine that with huge south facing windows, meant that in summer the front room hit 37c(98f) with the blinds drawn. Insulation and new windows with decent coating means that this summer (when outside was 40c) the livingroom's max temp was 27.5c this december we used 1500kwh of gas for heating. (compared to almost triple that in the house across the road.)
  • Tor3 4y ago
    Open fireplaces suck a huge amount of air from the room. It was once explained to me that in one particular case (a specific house) the open fireplace would typically suck 150 cubic meters of air every hour, when that was replaced with a wood stove it went down to 15 cubic meters/hour. So, an order of magnitude of difference. Those numbers shouldn't be taken as accurate of course, but at least that house got much warmer simply because they didn't have all that air sucked in from outside all winter.
  • dublinben 4y ago
    Those much reviled Insulate Britain folks might have been on to something after all.
    • dazc 4y ago
      Insulation in itself can cause more problems than it solves in some circumstances though, especially when it results in moisture becoming trapped within the fabric of the building. Cavity wall insulation is one such example where there was a mad splurge of works being done poorly and where inappropriate, the inevitable result being further works required to remove it and make good the damage caused. Insulate Britain's dream come true would be much more of the same.
• aga98mtl 4y ago
  In my part of Canada it is common to have mini-split (non-ducted) heat pumps, mainly for cooling. The salespeople like to say that you will save a lot on heating with a COP of 3. However the placement of the inside unit is always close to the ceiling, usually in the highest part of the house. This is perfect for cooling during summer. However during winter, it causes the upper part of the house to be hot and the floors to be cold. The basement resistive heaters have to compensate to maintain the target temperature. This means that these single head mini-split heat pumps cannot replace 100% of your heating and cannot provide the same level of comfort than resistive baseboards.
  • sokoloff 4y ago
    What you say is true, though another approach that could be more efficient is to simply run the heat pumps with a higher setpoint rather than supplementing them with [as much] resistive heat (especially in the majority of season that isn't the coldest design day). It might "feel wrong" to set the heat pumps to 25°C, but that could easily be cheaper and more efficient than setting them to 20-21°C and supplementing to the same level of comfort with CoP of 1 resistive heating all season long.
    • MonkeyMalarky 4y ago
      I have the same setup as GP and setting a higher temp doesn't help at all. My thermopump is in the main hallway on the second floor and blows towards the master and second bedroom, above the stairs. In summer it's great because it sends cold air everywhere and lets it sink to first floor. In winter, it just creates an insufferable hot bubble on the second floor. I already prefer to sleep in the cold and just use baseboard heaters on the main floor and bathroom. I don't even heat my bedroom.
      • BizarroLand 4y ago
        Sounds like a ceiling fan or some sort of air circulator is in order. If you put a ceiling fan on blow to push the hot air down it will blend with the air in the rest of your house and improve the overall comfort of your space. If that won't work, for instance your home is very boxy and separated, it might be worth looking into AC duct boosters on the far away areas to suck more air out of the ducts from farther away. If I misunderstood and you have a ductless system, they make electric fans that go in between paired walls and look like a ducted register, but that are very useful for blending air between two rooms. A few of those alongside a through floor to ceiling below fan duct might be available that could help even out temps in your house even more.
• cpsns 4y ago
  I have a heat pump and a wood stove in my house. The heat pump doesn’t do as good of a job, but it keeps one from freezing and it really shines in the summer at cooling the house. Heat wise the wood stove is much nicer. I can’t quantify why, but the quality of heating feels completely different and I’d much rather use it. Additionally as someone who has used a heat pump in -25C I dispute the claims they work well in the cold with personal experience. If I hadn’t had backup heat I’d have been way, way too cold as it didn’t heat acceptably at that temperature.
  • rayiner 4y ago
    Did wood stoves become a trend recently?
    • mindslight 4y ago
      It happens every time oil/gas spikes. Heating oil was just pushing $6/gal, so yeah. And the federal tax credit just got severely neutered. At least that's what caused me to install a new one at the end of last year as opposed to later this year. Wood stoves and heat pumps would seem to pair well. Heat pump capacity is expensive, and drops precisely when you need it most. Rather than falling back to resistive heat for the small amount of coldest days and watching your electric meter spin while you shiver, you can focus on the wood stove and have plenty of heat. On most days, you can keep a fire going if you're home and you want to, or you can just let the heat pump do its thing. Also unless you have a huge backup generator (and a correspondingly large fuel source), a heat pump isn't going to work in power outages while a wood stove will.
    • cpsns 4y ago
      Not where I live, in rural Nova Scotia almost everyone has one if not for primary heat, than for when the power inevitably goes out. People here are not well off and wood is hands down the cheapest heating option. In other places? Maybe it’s a fad/trend.
    • parrellel 4y ago
      The EPA was going to ban them, so everyone who still used one got very vocal, along with about a third of the state of Maine.
• alkonaut 4y ago
  I have both a larger return air unit which provides hot water for taps and radiators, and a smaller pump/AC on the wall which doesn't need to work at all in winter, but is useful for providing AC on the hottest days. The AC style pump heats OK down to very cold temperatures but I'm not sure what the efficiency is at -20, probably not great. A return air heat pump has no problem with cold temperatures because its not pulling heat from outside air, it's pulling heat from warm air that's sucked from the air about to be ventilated out of the house (what's drawn from vents in bathrooms and kitchens). So it cools it from say 20 to 0 deg and exhausts it on the roof, transferring that heat to the hot water system both for radiators/heated floors and tap water. This is similar to how a ground-heat pump works too. It also doesn't need to worry about freezing temps because the ground doesn't get that cold, especially with a deep enough hole. Those two forms (return heat and ground heat, are probably 95% of the heating solution for single family homes in my Swedish suburb). Very few would heat a home with either anything combustible OR with an outside air unit. Many have them, but mostly like I do as a complement or summer AC. I'd not recommend an outside-air heat pump for heating anywhere where it's regularly very cold. Much better to just set up a proper heat pump and connect it to a water based radiator system. You need to have some kind of ventilation in the house so no point wasting that heat by blowing hot air out the roof.
• supermatt 4y ago
  I love my heat pump. When it was -25C outside it was still performing with a COP of ~3. It is ground source - I have a large loop submerged in a large pond, so it is the temperature of the water (was low of 2C as read at the intake) that is important rather than the air temperature. It would likely be better in deep trenches (frostline here is 1.5m), but the installation cost in the pond was negligible, and meant i didnt need to tear up the garden.
  • SamBam 4y ago
    How do you measure your COP? I'm having heat pumps installed now, and am interested in how everyone has this information at their fingertips.
    • supermatt 4y ago
      My heat pump will say how much kWh of heat it has output (~2400kWh last month). I also have a separate electrical meter just for the heat pump that tells me how much electricity it consumed (~700kWh last month). I simply divide the heat output by the electricity consumed which gives me a COP of ~3.4. I can connect the meter to the heat pump, in which case the pump will use pulses from the meter to calculate it internally, but i havent set that up. I have no idea why it doesnt come with an integrated meter... seems like that would be easier tbh.
      • fomine3 4y ago
        It's interesting. I wonder how they measure heat output.
        • supermatt 4y ago
          not sure, but i guess its sampling the flow through and the delta-T across the condenser and doing whatever the relevant calculation is off that.
• zekenie 4y ago
  we switched to a heat pump last year and we’ve been mostly pleased. that said in the last cold snap when wind chill temps fell to -30 (we live in chicago) the entire system shut down! we talked to the installers and they said that when articles like this way “works down to -10” you have to understand that it’s the wind chill temp. also i’m sure there are other pumps on the market that would have faired better. we have a mitsubishi mini split.
• 0x5345414e 4y ago
  New refrigerants will make a big difference here. The main theoretical restriction is the pressure delta required to go from a low enough pressure to transfer heat into the system at a low ambient temperature, then to a high enough pressure to transfer heat out of the system at a high ambient temperature. That’s what causes the loss in COP at low temperatures—the increased work the compressor has to do. It’s definitely theoretically possible. There are refrigerants that can do this now with a relatively low delta, but generally they are flammable, toxic, or have high global warming potential. There are other ways around this like booster systems, but it becomes a $$$ issue at that point.
• jamiegreen 4y ago
  Does anyone know if they work in old houses? We have a stone house built in ~1800. We have upgraded with insulation in the floors, walls ceiling, but of course it is still fairly draughty if it is windy. It's damn expensive to heat, and have considered an air source heat pump, but always thought that it wasn't really a good idea for old houses.
  • MonkeyMalarky 4y ago
    There's no reason why it won't work, its just another (more efficient) source of heat.
    • Jochim 4y ago
      It might work theoretically but that doesn't mean it should be done in many cases. Where I live electricity is nearly 3x the price of gas. While some heat pumps can achieve this in certain conditions it eliminates most of the affordable options which raises the question of how long are you willing to wait before a £10k-50k+ investment pays itself off? They typically operate at lower output temperatures than existing systems. For example, swapping out a gas boiler for a heat pump will often require replacing all the radiators with much larger ones as well. IIRC they're also less responsive. You might find yourself keeping the house at 18-20c all day rather than turning off rooms you aren't using. The effect is that you use more energy than you would have otherwise.
      • MonkeyMalarky 4y ago
        Right, it is decision that depends more on the economics of where you live and your usage than the age or construction of your house. Where I live, gas is not an option and there are subsidies to change over to electric and off of heating oil.
  • dazc 4y ago
    I lived in such a house once and it was permanently cold, even with heating left on all day. In this instance the problem wasn't just the draughts but also the fact that it was connected to the old standard sized radiators that never got hot, they were always just above tepid, at best. The landlord will happily bore you senseless about how much money he's saved though.
• gandalfian 4y ago
  How's your Finnish? https://cooperandhunter.com/split/files/docs/support_20190201151407139.pdf https://cooperandhunter.com/split/files/docs/support_2019020... magazine review from 2019 I think. Says at -20F you still get around 3x COP energy ratio. On the other hand the air to air heat pumps they are testing cost three times as much as a regular one. Unfortunately they say the worst temperature is just above freezing where the air can still hold plenty of damp but quickly be cooled below freezing to turn the damp to ice... Cold but damp being the description of British winter. The American idea of winter air cracking with dryness and running a humidifier indoors doesn't really exist here. They are currently free of sales tax in the uk though. Tricky to work out which models are designed towards heating rather than cooling. Hopefull though but still begs the question if they are so great why are most people still buying night storage heaters and such? Just a lack of skills? Annoyingly they are only £600 for a decent japanese one and connected a £90 vacuum pump for half an hour, look at the guage to see if its holding a vacuum and then turn an allen key to release the gas. It looks not too hard but we are not allowed to buy them incase we pollute the enviroment with refrigerant, just out of reach...
• davidmurdoch 4y ago
  Unrelated, but Florida Code requires landlords to ensure working heat, but not cooling. Most heat pumps installed in Florida default to heating mode, and to switch to cooling mode a constant 24V needs to be sent to the heat pump's reversing valve. So if that valve, or voltage, ever fails when supposed to be in cooling mode you get cooked to 100F+ temps while you sleep, and burn out your heat pump while you're at it.
  • briHass 4y ago
    Most heat pumps made in the last 2 decades are computer controlled with a wide array of temp and pressure sensors. Stuck reversing valves do happen, but it's likely the unit will shut down due to an ambient outdoor temp, cool temps, or refrigerant pressures that are too high for heating mode. Not much different from a gas furnace. If somehow the computerized safety controls went bad and the unit ran without the blower fan, it would quickly overheat and destroy itself and possibly catch the house on fire. Luckily, these failsafe systems are well engineered with multiple redundancies. They aren't hacked together React apps.
• NelsonMinar 4y ago
  What has changed in air source heat pump design that they work better in cold climates than they used to? I know they do, curious what the engineering is.
  • fomine3 4y ago
    more powerful compressor, bigger heat exchanger, measures against snow and frost, better defrost implementation to avoid stop heating.
• fuoqi 4y ago
  The biggest issue with mass-scale installation of heat pumps is non-linear load on grid in cold weather. Failing efficiency and ultimately automatic switch to resistive heating causes electricity consumption spike, together with other accidents caused by the weather (be it reduced generation or grid damage) it can cause brownouts or full-blown blackouts. In other words, people can lose heating when they need it most. Any programs which promote heat pump installations above a certain scale must either include huge investments into grid robustness or mandate that all heat pump installation must include fuel-based backup heating sufficient for a week or two.
  • leetharris 4y ago
    This is why the technology is best combined with geothermal concepts. You only have to go a few feet deep to get warmth and that solves basically every problem a heat pump has.
    • starkd 4y ago
      Only a few feet deep? Maybe in select areas, but you generally have to go a lot deeper than that. It's been my understanding that the steep cost of geothermal involves the drilling. As much as $80K just to install a decent system, from what I've heard.
      • timbit42 4y ago
        Some geothermal systems use deep wells, others use coils of pipe buried a few feet down, below the frost line. If you're lucky enough to have a deep pond or lake nearby, you can put the coils of pipe in that.
        • starkd 4y ago
          In my understanding, it takes more to maintain such setups. Talking to the HVAC guys that do this for a living rather than just the scientists reveal more about the practical realities of these systems.
      • 4y ago
• mrbigbob 4y ago
  In the US the department of energy is having a challenge to heatpump manufacturers to manufacture a heatpump that will work all the way down to -20F (-29C). Both Trane and York have prototype models that meet this requirement and should be on sale in less than 2 years Here is an article discussing it https://electrek.co/2022/12/26/us-companies-are-producing-heat-pumps-that-work-below-20f/ https://electrek.co/2022/12/26/us-companies-are-producing-he...
  • briHass 4y ago
    It would be nice if they step up their game. The US has been clobbered over the last 15 years by the Asian heat pump/mini split brands like Mitsubishi, Fujitsu, Midea, and Gree. Most of the myths in this article come from experience with crappy American heat pumps that are as technologically out of date as a cell phone from the early 2000s.
• maxdo 4y ago
  If you use geo thermal in combo with heat pump, efficiency is even higher and you are not afraid even -40 -50c , you still save money. NY state will ban oil burners from 2025 for the new construction. Geo thermal is super easy just put few pipes under the ground and save money.
  • cycrutchfield 4y ago
    Define “super easy”. Last time I checked geothermal installation was quite expensive due to having to move a lot of earth for those “few pipes”
    • yxhuvud 4y ago
      There are two variants. One move a lot of earth and one drills deep holes. Both are pretty expensive though.
  • mikewarot 4y ago
    One variation of putting a coolant loop into the ground is to just cut a deep narrow trench and loop the coil in it like a slinky pushed "sideways".[1][2] [1] https://dandelionenergy.com/geothermal-ground-loop-frequently-asked-questions https://dandelionenergy.com/geothermal-ground-loop-frequentl... [2] https://www.energy.gov/energysaver/geothermal-heat-pumps https://www.energy.gov/energysaver/geothermal-heat-pumps
• alkonaut 4y ago
  It's interesting that every time this comes up, return air heat pumps are never discussed. It's always the AC-kind. Is there something about how ventilation is built in e.g. the US that prevents using return air for heating? Where is the air that's drawn from kitchens/bathrooms typically going in a reasonably modern US home?
  • LeifCarrotson 4y ago
    Return air heat pumps? It's telling that I have no idea what you're talking about, when I just this weekend pulled the wiring for the brand new heat pump that's literally being installed at my parent's house as I type this. We both have (had, in their case) a forced air natural gas heating system, with "cold air return" ducts which transfer air volume from the bedrooms, kitchen, etc. back to the furnace room so that the heating vents aren't fighting back-pressure. Air drawn from kitchens, bedrooms, living spaces, etc. goes back into the bottom of the furnace, where it's heated and returned to the house. There are two sets of ducts, one going away from the furnace and one going back to it. It's a closed system. You can't pull heat out of air in your air return, then pump that same return air through a heat exchanger to make it hotter than before. Sometimes, yes, air from the kitchens and bathrooms when you turn on the stove exhaust fan or bathroom fan is conveyed out of the house through a baffled wall vent by a PVC pipe (note that a sad number of bathroom fans eg. in old hotels and apartments, where getting ducts out of the building is impractical, are not actually moving air: they just make noise and don't go anywhere). But those dedicated fans are only turned on for a few minutes per day. Just about everything else is a closed system...older atmospheric venting water heaters and One thing that I would be interested to see is a clothes dryer that was energy-aware; I've got a newer, reasonably high-efficiency gas dryer but it does dump a lot of energetic hot and humid air into the sub-freezing exterior in winter, which is replaced by cold air getting pulled into the house, and it pulls my expensive cooled air into itself in summer, heats it, and blows it out, to be replaced by pulling in hot and humid summer air.
    • alkonaut 4y ago
      Return (exhaust) air pumps just use the heat in the air that was being evacuated anyway. Requires only that you have ducts from those rooms that are ventilated (usually kitchen and bathrooms) to the pump, and from the pump out to ambient. It’s not a lot of ductwork. This is for older houses here which have no forced incoming air. Bedrooms/livingroom just take in fresh air directly from outside. A more modern home would have heat exchange between in/out air to move the heat from the incoming to the outgoing air. Return (or exhaust) air pump: https://assetstore.nibe.se/hcms/v2.3/entity/document/121339/storage/MTIxMzM5LzAvbWFzdGVy https://assetstore.nibe.se/hcms/v2.3/entity/document/121339/... Those are cheap as hell. Handles all the hot water, space heating and ventilation in my home with a $5k device which has a COP similar to a wall unit + works when it’s really cold outside too.
• tootie 4y ago
  This tech has gone mainstream very, very quickly. PBS just ran a report on the pace of new installs in the US https://youtu.be/RdzjrVwWz4o https://youtu.be/RdzjrVwWz4o
• fwungy 4y ago
  Great system. The advantage of running gas to homes is to avoid the single point of failure in the event either the gas or electric delivery fails. Also, creating heat from electricity requires either a) massive amounts of sustainable energy b) nuclear or c) burning fossil fuels to create electricity, then sending it down the wire to become heat again. Under any condition except b), is massively inefficient. Trying to run a ton of electric heat off green power sources in a deep freeze would be a disaster.
  • pmontra 4y ago
    > The advantage of running gas to homes is to avoid the single point of failure I had a 10 minutes blackout today and my gas boiler heating radiators in all my house went off. I think that I'd need a UPS for the boiler if I don't want main power to be a single point of failure.
    • fwungy 4y ago
      If you have gas and heat running to your home you will have one if the other fails. We just had a 24 hour blackout at my house. The fact that we had gas allowed us to remain in the home with hot water, stove and heat without too much inconvenience. One day without that wouldn't have been terrible, but other people nearby lost their electricity for days, which would be very hard without gas.
      • pmontra 4y ago
        My point is that I would have no heat. I could cook and have some hot water because I could warm it up in a pot.
• Yaggo 4y ago
  I just had installed three Mitsubishi RW25 heat pumps, latest tech which works with efficiency factor of two in -30 C (-22 F), and still produce their nominal heating power of almost 4 kW in -20 C. I live in southern Finland so we rarely even experience such low temperatures. Very good ROI. Independent test in Finnish: https://www.scanoffice.fi/wp-content/uploads/sites/11/2022/09/eufi29-21005116-t1.pdf https://www.scanoffice.fi/wp-content/uploads/sites/11/2022/0...
• electric_mayhem 4y ago
  Mine is cheaper to run than my 97% efficiency gas furnace down to 5 degrees F.
• dahfizz 4y ago
  Let's do some basic math: The US average cost of electricity is 16 cents / kwh [1] The US average cost of Natural Gas is $10.84 / thousand cubic feet [2] A thousand cubic feet of natural gas contains around 300 kwh of energy [3] So natural gas is around 4 cents per kwh. Gas furnaces are extremely efficient, buts lets round up to 5 cents/kwh to be conservative. So a heat pump needs to maintain a COP of 3 just to be in the same ballpark as natgas in terms of cost, and closer to a COP of 4 to be cheaper. Heat pumps "work" down to -20F or so, but the efficiency severely degrades. Heat pumps as a sole heat source are not cost competitive in cold climates. I have a heat pump in New England, and it is wonderful for 3 seasons of the year. I think all new construction should have one. But the cost to heat during winter is ridiculous. I am very glad I had an auxiliary natgas heater put in. [1] https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a https://www.eia.gov/electricity/monthly/epm_table_grapher.ph... [2] https://www.eia.gov/energyexplained/natural-gas/prices.php https://www.eia.gov/energyexplained/natural-gas/prices.php [3] https://www.eia.gov/energyexplained/units-and-calculators/ https://www.eia.gov/energyexplained/units-and-calculators/
  • kennywinker 4y ago
    The full cost of fracked methane gas is not actually included in the price. I'm not just talking about the environmental cost: gas consumption and production is subsidized by tax dollars, and the health costs are poorly quantified but my understanding is a growing body of evidence links gas usage in the home to childhood asthma and other chronic health issues.
    • dev_tty01 4y ago
      The asthma issue is with gas stoves. It is irrelevant with respect to a proper gas furnace. None of the exhaust from a modern furnace enters the home air supply. By the way, if you are going to consider environmental costs for gas you should also consider those costs for electric.
  • Kirby64 4y ago
    One note on energy in nat gas: that assumes 100% efficient gas furnace. Cheaper furnaces are ~80% efficiency. Really good furnaces are ~95% efficiency. Adding natural gas infrastructure to a building that does not currently have any is extremely expensive, even if the natgas furnaces aren't particularly expensive themselves. I agree it's cheaper if you have it now, but that assumes you already have a gas furnace. I think the fear for most people is that natural gas can easily become substantially more expensive. European natural gas pricing is currently ~$20/mcf, and spiked to ~$80/mcf for some time. Natural gas pricing limits you to a single source for power... whereas power inherently has many sources it can come from. If natural gas becomes more expensive... you're stuck paying more with the furnace. With heat pumps, there's options available to alleviate pricing either for producers or for consumers (namely, solar for consumers). Also, importantly on the COP point: you need to talk about the area under the curve in terms of cost. Although it may be more expensive per unit of heat when COP drops below ~3, you have to think about it in terms of overall cost. A furnace will be the same efficiency if it's -50F or if it's 50F outside (for the most part...). So for the periods when it's mild, but heating is still required, the heat pump is an obvious winner. I suspect that the math works out in favor of heat pumps, even with reduced efficiency during winter, for many climates. The only thing is that you'll get a much more peaky power bill. Obviously there's exceptions, but there's vast swaths of the world where a heat pump is going to make a ton of sense.
• semi-extrinsic 4y ago
  More than half of all homes in Norway have had an air-to-air heat pump retrofitted. It is mandatory for all new construction. Case closed.
• witnesser2 4y ago
  if carnot diagram is drawn, it will show nothing cheap. try to recall thermal dynamics taught many years ago. heat pump works well when the exterior temp differ not much from interior temp. Namely for places like Cal and Tex, still the winters need heating. if it is freezing temperature, much energy will be spent on the mechanical part. Literally an electric heater but maybe less efficient than an interior heater by your knee. Not very logically coherent. Recall the professor's words. thermal dynamics is a very chilling subject, basically demysterifying fundamnetally and establish a solid view of engineering. Its experiments were repeated by millions of engineering students, the rules derived still hold firmly on earth so far.
  • kenmacd 4y ago
    The Carnot limit of heat pump heating from -25C (-13F) to 20C (68F) is over 6.5. That's 650% efficient. There's a lot of heat in our 'cold' air. If you're going to try to claim 'thermal dynamics' [sic] you should at least do the math on it first: 1 / (1 - (248.15/293.15))
• mikewarot 4y ago
  Of course if you can have a in ground coolant loop, you can do even better.
• Krisjohn 4y ago
  These are "Split Systems", yes?