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How a heat pump works

246 points by WatchdogReset 4y ago

WatchdogReset 4y ago
The heat pumps are one of the means of heating (and air conditioning) in the heart of the news. What is their principle of operation. You can ask questions here if there are points to clarify in the course
- jcstauffer 4y ago
  I'd like to get a heat pump to replace my existing baseboard hot-water system (currently powered by an oil furnace) without converting to a heated air system. From what I've read, that's not quite feasible yet, since current systems can't produce a high enough temperature. What are the prospects of that technology becoming viable in the next few years?
  - zacharybk 4y ago
    It partially depends on your climate. I’m in Portland, Maine, so for us, we have a natural gas furnace with radiators, but they’re heavily supplemented by a few heat pumps. For us, the temperature frequently gets very low in the winter, sub 10°F, and this is the point when heat pumps aren’t as efficient. An ideal set up in a small home could be heat pumps running off solar and a woodstove for when it gets really really cold.
  - suoduandao2 4y ago
    Solar hot water would probably be a better fit for your situation.
  - sokoloff 4y ago
    Figure out the minimum flow (supply) temperature that can meet your building heat loss on the design day. If you have enough radiation, you might be able to get by with 135°F flow. I have baseboard in the attic and cast iron rads on the main level. I have the flow set to 126°F until the outside air temp drops below 30°F and then I increase by 2°F for every 4°F change in OAT. So at 2°F OAT, I have 140°F flow. That’s enough to maintain temp in my fairly poorly insulated 1920s house near Boston. It’s enough to slowly recover temp as well. 140°F is a stretch for air to water heat pumps, but you could reasonably use an A2W for most of the year and supplement with a 9kW (31KBTU/hr) electric boiler as emergency supplemental heat and use that a couple days per year. What killed it for me (and the reason I have a fairly new gas boiler installed) is the upfront cost was utterly uncompetitive. If you have a condensing boiler, set the high-limit or flow temp to 130-135°F and see how your house handles it on the cold days. You can measure and calculate all you want, but nothing beats trying it.
  - LazyMans 4y ago
    This guy is a great resource if you want to understand what goes into a proper A2W system install. In Europe, it seems by law they are required to do heat loss calculations to size an install. In the US, it seems to be a little more loose. https://www.youtube.com/watch?v=0IvGe4JZLSU https://www.youtube.com/watch?v=0IvGe4JZLSU
    - mikeyouse 4y ago
      I saw a video recently from a ... less sophisticated place in the US... where the HVAC installer literally held up a piece of paper from the street with different sized houses on it, and sized the HVAC based on which of the houses best "covered up" the actual house when looking through the semi-transparent paper. Just astonishing. No consideration at all for the build quality/insulation details, no adjusting for the distance from the road, just a "welp, this looks like a 3-ton job".
      - LazyMans 4y ago
        That's insane. Proper sizing is paramount, it's also a good way to surface that 5k in insulation improvements might be the better first step to consider vs installing a larger system just to keep up with losses.
  - sbradford26 4y ago
    So CO2 heatpumps are starting to become available in the US which can run higher temperatures. But most likely the best option would be to switch to radiators that don't require as high of temperature to operate. Something like underfloor heating or panel radiators. The other option that is common in New England is to keep the baseboard oil heat and get mini splits. Then run the mini splits for heat and if they cannot keep up switch to the oil heat.
  - hcknwscommenter 4y ago
    What works for me in the northeast with an old house is a high velocity small duct air handler/distribution system (unico) coupled with a Bosch cold climate heat pump, with an oil furnace backup. This is forced air, so not exactly what you are looking for and I get that the heat from those baseboards is a better quality/less drying form of heat. I could upgrade to add a whole house humidifier to address this a bit. I use the heat pump most of the year, down to an outside temp of about 25F, although Bosch says I should be good down to 5F. The oil furnace runs basically Jan/Feb (but not as much this Feb as it's like 50F today). I've also extensively sealed/insulated the house (although there's always more of that to be done in an old house). It's a pretty good solution. I'd love for the air to water heat pump tech to work better, but I got tired of waiting.
  - masklinn 4y ago
    > From what I've read, that's not quite feasible yet, since current systems can't produce a high enough temperature. Is it because baseboard hot-water systems have limited exchange surface surface and thus need very high temperatures to do anything?
    - mikeyouse 4y ago
      Yep - exactly the issue. They've started shipping much more efficient baseboard systems which run at lower temps by adding more fins, adding CPU fans to increase heat transfer across the plates, etc. but the correct answer is to usually invest in air sealing/insulating the house which will require fewer BTUs in the first place.
  - WatchdogReset 4y ago
    I think this is possible. I will ask to a teacher of hvac-learning and come back to you asap. But basically you can heat water instead of air with a heat pump.
  - WatchdogReset 4y ago
    As others comments said, it depends on the climate : The problem is that the power/performance of the heat pumps decreases with the cold weather and the necessary increase in the temperature of the heating water, which obliges to keep the boiler for the cold weather. This is a problem for the heat pumps without probable solution and little progress to wait. The solution is to insulate the house very well so that its needs can be covered by the heat pump with less hot water. Divide the losses by 2 at least.
mastermedo 4y ago
I'm getting an error when trying to load the page: > Error establishing a database connection https://web.archive.org/web/20230210134443/https://hvac-learning.com/courses/heat-pumps-part-1/ https://web.archive.org/web/20230210134443/https://hvac-lear... The archive.org is pretty slow on this one as well, as it is an interactive site.
- Neil44 4y ago
  OOM Killer strikes again - it always loves mysqld for some reason...
  - WatchdogReset 4y ago
    If you have advice for me, I'll take it ;) can exchange with HVAC courses
- WatchdogReset 4y ago
  The website is new and not fit yet for such numbers of visit, so sometimes it does not render well pages. I(admin) still in the process of understanding how to build a nice website. I will analyze what happened and enhance it. I'm sorry for the inconvenience !
deleted 4y ago
[deleted]
yreg 4y ago
Technology Connections has a good video on heat pumps. (Actually several of them, I link the newest one.) https://www.youtube.com/watch?v=MFEHFsO-XSI https://www.youtube.com/watch?v=MFEHFsO-XSI
- generaltsos 4y ago
  That channel is fascinating. They have created some incredibly interesting projects.
  - manigandham 4y ago
    What have they created? You might be thinking of Tech Ingredients - https://www.youtube.com/@TechIngredients https://www.youtube.com/@TechIngredients
    - generaltsos 4y ago
      You're spot on - I am subscribed to both so I confused them without opening any links. Technology Connections is fascinating in its own right as well.
- pkulak 4y ago
  I just found this guy too. He answered a lot of questions I had about efficiency and use below freezing. https://youtu.be/fxEqVuiHhM0 https://youtu.be/fxEqVuiHhM0
  - kenmacd 4y ago
    I like his videos, but I don't trust his numbers in this one. He shows a COP of ~1 when it's 10 degrees out. These are the easiest possible conditions for the HP, and where all the specs show the highest COP. His graph showing the HP is running equal to a baseboard heater seems very suspect.
    - pkulak 4y ago
boringg 4y ago
What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HVAC installers / heat pump manufacturers and governments are all pushing this hard right now. I believe in the benefit for most people and the climate benefits are great. I am always concerned on when there is large consensus on a hard push - worth looking at who the winners are and what the trade offs are.
- nashashmi 4y ago
  Heat pumps are the opposite of AC. AC industry is behind this for sure. It is like a paid PR campaign. It is not more economical then gas. So now gas is going to be punished for factors X,Y,Z. It is coordinated. I wish there is more investigative research into who and why they are doing this.
  - WatchdogReset 4y ago
    For the record, I am only trying to make my elearning website more known. There is plenty of other HVAC subject that I would like to share. It's just that Heat Pump where for me an interesting topics to get into the subject but you can have a look at other free courses.
  - mikeyouse 4y ago
    Ah yes, "big AC" is bullying the Oil and Gas industry with their subversive marketing. If only Exxon, BP, and Shell had some political clout they could expose this plot.
  - jamiek88 4y ago
    In this thread you’ve gone form ‘compressors don’t work like that’ to ‘this is all a conspiracy by big A/C’. You are not engaging with any of the helpful, generous replies, in fact going as far as to say that you wish you could call it ‘coordinated’. Why are you even here if you think we are all lying shill for big air compressor?
beardyw 4y ago
Error establishing a database connection
- WatchdogReset 4y ago
  The site is pretty new, I(admin) am not used to have lots of traffic. I will analyze what happened and chose better solution. I am sorry for the inconvenience !
Bhilai 4y ago
Definitely a lot of posts about heat pumps on HN recently that this topic has piqued my interest but only to the point that I want to know if I can install one in my home. Are there any legit resources out there that can help me understand if heat pump is a right choice for my home based on Geo, type of home, sqft and other factors to consider before replacing current systems (two ACs and two furnaces?)
- hcknwscommenter 4y ago
  My $0.02 are that any competent and honest HVAC company will be able to walk you through the concepts of your home's heating/cooling load etc. and what size heat pump can meet that need, what it costs to run annually, and what incentives there are. It's not that hard. I would reach out to three highly ranked (or word of mouth suggested) HVAC co's and start the conversation.
- rapsey 4y ago
  I guess they are a new thing in the US. In Europe installing a heat pump with floor heating is done for practically every new family house. It is the cheapest (for us) and nicest way to heat up your home. Though very few people build houses out of wood, unlike the US.
  - gautamcgoel 4y ago
    What are the houses usually made of? Stone?
    - rapsey 4y ago
      Engineering/perforated bricks mostly. North Germany/UK is a lot of solid red/gray bricks, not sure if new homes still use that style, since it has terrible insulation. If built with perforated bricks a home will also put a thick layer of styrofoam for insulation on the outside.
- gwbas1c 4y ago
  Generally, they can work anywhere in the continental US. (Assuming you live in the US.) If you're in northern NH, NY, VT, or Maine, you might want to keep your gas system as a backup. (New homes tend to have electric backup, but if you have an older home they just keep your furnace as backup.) I have a 3000 sqft house in MA with a heat pump as my primary heat, and an electric strip as backup. The heat pump goes into the ductwork for most of the house. I generally haven't had problems. (It did have to be adjusted because it was the first time the installer put one in.) I have solar and usually get 1-2 large bills in January and February, and then March and April are very cheap, if I get a bill at all. My "large" January and February are comparable to what I'd spend on conventional heat. Last weekend we had a "once in a century" cold snap down to -4. Most of the house was at temp, but one room fell to the high 50s. From what I've heard, plenty of people with conventional heat had far worse issues than a chilly room.
kebman 4y ago
Looks like the HN posting crashed the site.
- WatchdogReset 4y ago
  The site is pretty new, I am the webmaster, maybe I should analyze the log and choose better hosting. I am sorry about the inconvenience!
  - kebman 4y ago
    No worries, I'll take a look at your site later. :) If it helps, I tried reaching the site from Norway. Thanks for reaching out! Edit: It works just fine now! Looks pretty interesting!
asow92 4y ago
As someone who lives in the northeast and has a 3600sqft home, I'm wondering how many heat pumps it would take to replace my gas steam boiler system. I'm not sure if heat pumps would be cost efficient given those parameters.
- prottog 4y ago
  In the Northeast with that much square footage, you would be better off with ground-source heat pumps (whether open or closed loop), rather than the normal air-source heat pumps.
  - asow92 4y ago
    I guess the concern I have with all this is that my current system works well, and I don't want to spend $10K+ unless it brings down my heating costs significantly. Could a ground-source heat pump system do that?
    - zeroonetwothree 4y ago
      It depends on relative prices in your area so we can’t answer that. You would have to calculate it yourself. Typically it makes the most sense to do when you need to replace your system.
    - sbradford26 4y ago
      Ground source/geothermal would significantly reduce your heating costs but it would be significantly more than 10k. For that large of house something like 40k+ wouldn't be out of the question, with the largest expense being drilling. I personally think geothermal is great, sadly New England's geography makes getting a ground loop installed more difficult. In the midwest lots of people would do a horizontal loop by trenching like 8 feet underground laying pipe in there. In many parts of new england that isn't really viable with all the rock so vertical drilling is used which is significantly more expensive.
      - snuxoll 4y ago
chem83 4y ago
I’ve had Mitsubishi heat pumps in a condo in the northeast for 3 years and they’ve worked great. No other heating sources here. I keep them on all day, which the mfgt discourages. My main gripe was their kumo cloud and Wi-Fi connectivity but they’ve since fixed firmware and the cloud side and it works much better.
YellowTech 4y ago
Seems like OP just performed a stress test on his website as he is the "Webmaster of https://hvac-learning.com https://hvac-learning.com an HVAC elearning website"[1]. Hopefully you can figure out something! Thank you for educating about such technology! [1] from WatchdogReset's profile about
- WatchdogReset 4y ago
  I am sorry for the inconvenience. I am still learning how to build a nice and efficient website. I will analyze what happened and try to fix and enhance !
  - scrollaway 4y ago
    I love that you're building free educational resources, especially about something like this! If you need help/advice to help build your website, email me (see my profile), I'll be delighted to help pro bono. :)
endisneigh 4y ago
I wish, wish wish there was a portable mini split (not a portable air conditioner). The closest thing is this: https://rollibot.com/product/mini-split-ac-room-air-conditioner/ https://rollibot.com/product/mini-split-ac-room-air-conditio... but it sucks. I don't understand why these things have to be permanent fixtures of your house, necessarily.
- bilsbie 4y ago
  I’m confused what you’re asking for (and why) but it sounds interesting.
  - endisneigh 4y ago
    A portable machine to provide heat and cooling via heat pump technology. For cooling this exists in many forms: there are the window air conditioners, and "portable" window air conditioners which have a duct that connects to the window. The problem with the latter is that they're loud and the ducts result in a lot of heat loss. For heating there are some portable air conditioners that use a heat pump but they're subject to the same issue described above. More common is resistive electrical heat in the form of coils or an oil filled container that radiates heat. A portable mini split, where it connects through the window would give you a similar advantage as a portable air conditioner, but with more efficiency and being less loud.
    - bilsbie 4y ago
      Cool idea. So a two piece portable with a just coolant line going through the window to the outdoor part?
      - endisneigh 4y ago
        yeah, exactly. there's a company called MRCOOL that does something similar (https://mrcool.com/diy-4th-generation/ https://mrcool.com/diy-4th-generation/), but the head (the indoor part that provides the heat/cooling) is designed to be mounted permanently if this were popular you'd see old houses retrofitted with pluggable holes where you could feed the lineset through and seal as necessary for temporary heat/cooling, or perhaps even permanent. the installation would be substantially easier if these were like 6000BTU instead of minimum 12000BTU per head, so it could be run on say, ~8 amps and be plugged inside.
rr888 4y ago
I just dont like moving parts. My problem with heat pumps is that you have to replace every 10-20 years which seems wasteful.
- kupopuffs 4y ago
  Do you own a heater that has lasted more than 10 years?
  - bluGill 4y ago
    The furnace in my house is from 1970 and still works. I don't want to know how inefficient it is. (I just upgraded the insulation of the house, replacing the furnace is a future problem)
- timbit42 4y ago
  My heat pump has a CoP of 3 and paid for itself in 10 years. New heat pumps have a CoP of 4 or higher and might pay for themselves in less. How much material in a heat pump is recyclable and how much isn't, compared to a furnace? We are trying to reduce CO2 and methane in the atmosphere. Throwing away the non-recyclable parts of heat pumps isn't as big of a concern. Polluting the ground and water isn't even as big a concern. Certainly they are concerns, but they pale in comparison.
boringg 4y ago
Oh I have a question for the community here about heat pumps. I have three mini splits that I use for AC but connecting them to a home hub is bananas amount of work and inconsistent (Mitsubishi brand). I wish there was a legitimately good, robust system to connect AC units to my smart thermostat (Ecobee) or even some of the other devices I have. It still feels the wild west for home energy systems - and the costs are quite high for the value they provide.
- mataug 4y ago
  So far I've been happy with using the mysa ecosystem for my smart home. It works with Apple HomeKit, its had relatively good reliability and the team behind the product have been responsive when I do face issues. https://shop-us.getmysa.com/products/mysa-ac https://shop-us.getmysa.com/products/mysa-ac From a technical perspective its just a IR remote with a wifi connection and a touch UI, but for controlling mini-splits it works great in my home.
spikej 4y ago
Genuine question that I haven't been able to find a clear answer for: are heat pumps now different from air conditioners two to three decades ago? (other than the fact that they heat and cool) Memory is fuzzy but I remember when I was a little kid and even captain planet cartoon showed air conditioners being bad for the environment... Or is it that heat pumps are better than the fossil fuel counterparts and so if you're going to do something bad you might as well do something less bad?
- Calvin02 4y ago
  It is the latter. Heat pumps are much better for the environment compared to the other sources of heating. Depending on where you live, you still need to heat your place and if so, heat pumps are better than other traditional methods like natural gas, wood, oil, or electricity. Similar to air conditioning, if you want to minimize your impact on the climate, you could set your temperature lower in the winter and put on a few more layers and/or set the temperature higher in the summer to minimize your usage of heat pump/air conditioner. This puts less pressure on the grid and demand for electricity generation.
- bagels 4y ago
  Captain Planet is not a reliable source of information. Air conditioners use electricity, the generation of which can cause fossil fuels, but also can come from other sources.
- ccooffee 4y ago
  > even captain planet cartoon showed air conditioners being bad for the environment That seems like it was a useful simplification for a children's cartoon, but things aren't that black-and-white. 1. Without air conditioning (or some other method of cooling and humidity control), almost all high-occupancy buildings would reduce their effectiveness as a work-place or living-place. OSHA has guidelines about office temperature (68-76, iirc), humidity, and overall air quality (e.g. pm2.5 levels). 2. The 1980s-era backlash against air conditioning was likely inspired by then-new knowledge about atmospheric ozone depletion. It was known that CFCs and bromine-containing compounds contribute to ozone depletion. It just so happens that CFC were common refrigerants (and aerosolizing agents). Refrigerant leaks from an air conditioner in those times released nasty stuff. CFCs are very rare (and restricted) in modern air conditioner / hvac systems. We instead use other chemicals which are not ozone depleters. (Though I believe that the theoretical performance of modern refrigerants is often not-as-good as the old CFCs.) 3. Running the air conditioner in a single family home is not terribly efficient, as (in most single family homes) most of the home is just empty space. Cooling bodies directly (e.g. cooling blankets, misting fans, etc) is more energy-efficient in these situations. Perhaps the more nuanced advice would be to use air conditioning to make the space "tolerable" but use direct cooling to make a space "comfortable". (This advice also applies to heating a space. I keep my thermostat between 60 and 65 and use blankets, small electrical resistance heaters, and drinking hot water as ways to temperature-regulate.)
energ8 4y ago
I have seen repeated claims of heat pump CoPs improving over decades. Can anyone summarize or provide links to what improvements are being made? Compressor technology? refrigerants? Fans to move heat? all of the above? Where is the path from here?
- LazyMans 4y ago
  I can provide a likely incomplete summary of the improvements. Compressors themselves have gotten much more energy efficient, although I'm not sure the impact on CoP is all that great since and waste heat from the compressor is being deposited in the home anyway. Variable speed compressors are the most efficient you can get pretty much. Refrigerants have improved in someways, but not really in others. Since heat pumps could be running with exterior temperatures that are quite low, with the system under pressure, some refrigerant blends would have less than desirable vapor pressures leading to problems running in very low temperature conditions. For the most part, the changes to refrigerant blends have been related to their Global Warming Potential (GWP). Expansion valves are a very important piece of a refrigerant loop, these used to be fixed orifaces. Nowadays these are dynamic, meaning they can increase efficiency of the system by metering the flow based on system load and other characteristics. These are called TXVs or Thermostatic Expansion Valves. Electronically controlled expansion valves are now hitting the market further increasing efficiency. Finally there is the design of the interior and exterior coils. I dont think materials have changed much, but the surface area has changed. You may noticed a 2 ton unit from 1997 is about 1/4th the size of a 2 ton unit from 2022. More surface area on the coil for the exterior unit lets you extract more heat from the air without burning a ton of energy running the fan super hard. Interior air handlers have probably improved some as well, variable speed motors, etc. Variable speed really is nice because you can get much more consistent temperatures in the home and wont get blasted in the face with heat from vents when a regular system cycles on and off.
- Freestyler_3 4y ago
  refrigerants (though some regulations have negative impact on this), Optimizing (DC motors and computers with sensors figuring out what is the best setting), Absorbing waste heat from the process, Insulation, Materials that stay more clean or self clean.
molsongolden 4y ago
Calvin (Segment) and Baker (Plaid) also recently put together a nice up-to-date heat pump info page and a heat pump vs. existing HVAC calculator. https://heatpumpshooray.com/ https://heatpumpshooray.com/ https://calv.info/heat-pumps https://calv.info/heat-pumps
- raldi 4y ago
  What do you mean by Segment and Plaid?
  - kaveet 4y ago
    Calvin French-Owen is the founder of Segment and Baker Shogry was Head of Product at Plaid until recently.
hbarka 4y ago
It's worth mentioning that there are many heat pump makers now using CO2 as the refrigerant versus the older environmentally harmful ones.
vladgur 4y ago
I live in SF Bay Area 20 minutes south of SF and I don’t have and don’t need A/C, so my HVAC needs are met by a gas furnace that is 10-15 years old at this point but it still works. Another caveat is our electricity ranges from 30 to 35 cents per KWh and is probably second to Hawaii in terms of cost. So I do check the cost of operating a Heatpump in the winter and due to high cost of power I am sticking with our gas furnace. If and when I go solar, I may reconsider, but for now gas is simply cheaper
- ericpauley 4y ago
  As high as that is, it looks like the price of gas in SF is (relatively) even higher. $4.50 a therm per Google, or $0.15/kWh. A heat pump would only need a COP of 35/15=2.33 to be a better deal (very likely since it will never be that cold in SF, and you get air conditioning for the very few days you might want it).
- stavros 4y ago
  As the Technology Connections video linked here mentions, "if it’s more expensive to use the option that saves energy... that’s a problem".
- liminalsunset 4y ago
  TL;DR a heat pump isn't worth it in Vancouver, BC, for me anyway. As a counterpoint to what seems to me like extremely high rates for electricity, as of right now in Vancouver, BC, Canada, I recently calculated that a heat pump would cost about ~2.5-3.5 cents per kWh of heat energy vs ~4.5 cents for gas heating at 80% efficiency. Power on average is about $0.10 USD per kWh here and gas is about $10 USD per GJ. The average house here uses 74.3 GJ of gas per year, or $ 743 USD of gas. We would save 413 $ per year by switching over. The neighbours next door spent $ 17000 USD to install a multi-zone heat pump, which still doesn't exactly cover every room. It's a Samsung, so by the general sentiment about their appliances here, we'll assume it doesn't last longer than 15 years and needs to be replaced at a cost of 12000 $ USD down the line. The hot water, low efficiency 80% boiler has lasted 35 years so far. Total cost of maintenance and repairs has been under $1500 USD. We expect it to last another 30 years easily because there is absolutely nothing special, fragile, or expensive in this system. Most of the spare parts can be found by walking down the alley and seeing which neighbour fell for the "replace your heating system" salesman tactics. If we replaced it with a "high efficiency" condensing type, we would save at most 20% on our gas bill (143 USD a year). The cost to install will be easily $5000. As a reward for doing so, we will have to pay for maintenance every 5 years at $200, and the device will fail and need to be replaced for another $4000 after 15 years. This is a statistical and practical certainty because condensate is corrosive. For the next 30 years, the old boiler we have will cost 23790 USD in total. Upgrading to a high efficiency boiler will cost us $28032 USD in total, not including ANY breakdowns Using a heat pump will cost $38900 USD in total, not including any maintenance, which you ABSOLUTELY need to do otherwise it smells and grows mould. (we do this maintenance ourselves but the design of the unit is ghastly, I curse the designer out loud every time I think of it, and this is a MAJOR pain to do.) Based on this math, there is absolutely no reason we would ever consider making any of these changes. A plumber tried to suggest something like this and they seemed to agree. With this said, I have a heat pump in my room, originally installed because I had too many computers and I needed air conditioning. We bought the absolute cheapest unit we could find at 700 USD and it has been wonderful. It has a capillary tube instead of an EXV because it's cheap, but it works "fine" down to -5 and it rarely goes under that here. The greatest benefit of a heat pump has nothing to do with energy efficiency or savings. The greatest benefit is that every room can have their own heating and cooling controls that respond FAST. I turn it up and down all the time when I feel like it and it's wonderful.
vladgur 4y ago
Is there a good calculator where I can enter my cost for units of electricity and gas and it will tell me how much operating a heat pump will save me over a gas furnace
- timbit42 4y ago
  To get a useful answer, you would have to put in more information. How many floors? How many sq ft per floor, what is the R value of your house? How cold can it get in the winter? How often is it that cold? Are you asking about air-to-air or ground-source heat pumps? The best thing to do is to get one or more local installers to give you an estimate.
billiam 4y ago
The other issue here in SF and near the coast is that for older, poorly insulated homes and those with high ceilings (mine are 12 feet), the real problem with an air heat pump is how slow it is to heat the volume. Unless you want to pay to keep your house warm 24-7 it will take an hour to warm up the whole house. I would love to kick my 10 year old forced air gas furnace to the curb, but I don't see how, even if I get solar. Contractors are charging a fortune for installing heat pumps these days too.
- fragmede 4y ago
  But, at 3x the efficiency of a traditional gas furnace, it may still be cheaper to heat the house all day, or have it start heating at 4:30 pm.
- timbit42 4y ago
  Heat pumps aren't meant to be turned on and off. In fact, they aren't meant to have the thermostat changed either, even at night. You set it to what you want and it keeps it there. Once it gets the temp where you set it, it doesn't use much electricity to keep it there unless it is very cold, like below freezing and especially below -20C. Due to your high ceilings, it might be prudent to install ceiling fans to help circulate the heat, but I'm not a heating expert so I recommend asking one.
kerpotgh 4y ago
[dead]

246 points by WatchdogReset 4y ago

The heat pumps are one of the means of heating (and air conditioning) in the heart of the news. What is their principle of operation. You can ask questions here if there are points to clarify in the course

jcstauffer 4y ago
I'd like to get a heat pump to replace my existing baseboard hot-water system (currently powered by an oil furnace) without converting to a heated air system. From what I've read, that's not quite feasible yet, since current systems can't produce a high enough temperature. What are the prospects of that technology becoming viable in the next few years?
- zacharybk 4y ago
  It partially depends on your climate. I’m in Portland, Maine, so for us, we have a natural gas furnace with radiators, but they’re heavily supplemented by a few heat pumps. For us, the temperature frequently gets very low in the winter, sub 10°F, and this is the point when heat pumps aren’t as efficient. An ideal set up in a small home could be heat pumps running off solar and a woodstove for when it gets really really cold.
- suoduandao2 4y ago
  Solar hot water would probably be a better fit for your situation.
- sokoloff 4y ago
  Figure out the minimum flow (supply) temperature that can meet your building heat loss on the design day. If you have enough radiation, you might be able to get by with 135°F flow. I have baseboard in the attic and cast iron rads on the main level. I have the flow set to 126°F until the outside air temp drops below 30°F and then I increase by 2°F for every 4°F change in OAT. So at 2°F OAT, I have 140°F flow. That’s enough to maintain temp in my fairly poorly insulated 1920s house near Boston. It’s enough to slowly recover temp as well. 140°F is a stretch for air to water heat pumps, but you could reasonably use an A2W for most of the year and supplement with a 9kW (31KBTU/hr) electric boiler as emergency supplemental heat and use that a couple days per year. What killed it for me (and the reason I have a fairly new gas boiler installed) is the upfront cost was utterly uncompetitive. If you have a condensing boiler, set the high-limit or flow temp to 130-135°F and see how your house handles it on the cold days. You can measure and calculate all you want, but nothing beats trying it.
- LazyMans 4y ago
  This guy is a great resource if you want to understand what goes into a proper A2W system install. In Europe, it seems by law they are required to do heat loss calculations to size an install. In the US, it seems to be a little more loose. https://www.youtube.com/watch?v=0IvGe4JZLSU https://www.youtube.com/watch?v=0IvGe4JZLSU
  - mikeyouse 4y ago
    I saw a video recently from a ... less sophisticated place in the US... where the HVAC installer literally held up a piece of paper from the street with different sized houses on it, and sized the HVAC based on which of the houses best "covered up" the actual house when looking through the semi-transparent paper. Just astonishing. No consideration at all for the build quality/insulation details, no adjusting for the distance from the road, just a "welp, this looks like a 3-ton job".
    - LazyMans 4y ago
      That's insane. Proper sizing is paramount, it's also a good way to surface that 5k in insulation improvements might be the better first step to consider vs installing a larger system just to keep up with losses.
- sbradford26 4y ago
  So CO2 heatpumps are starting to become available in the US which can run higher temperatures. But most likely the best option would be to switch to radiators that don't require as high of temperature to operate. Something like underfloor heating or panel radiators. The other option that is common in New England is to keep the baseboard oil heat and get mini splits. Then run the mini splits for heat and if they cannot keep up switch to the oil heat.
- hcknwscommenter 4y ago
  What works for me in the northeast with an old house is a high velocity small duct air handler/distribution system (unico) coupled with a Bosch cold climate heat pump, with an oil furnace backup. This is forced air, so not exactly what you are looking for and I get that the heat from those baseboards is a better quality/less drying form of heat. I could upgrade to add a whole house humidifier to address this a bit. I use the heat pump most of the year, down to an outside temp of about 25F, although Bosch says I should be good down to 5F. The oil furnace runs basically Jan/Feb (but not as much this Feb as it's like 50F today). I've also extensively sealed/insulated the house (although there's always more of that to be done in an old house). It's a pretty good solution. I'd love for the air to water heat pump tech to work better, but I got tired of waiting.
- masklinn 4y ago
  > From what I've read, that's not quite feasible yet, since current systems can't produce a high enough temperature. Is it because baseboard hot-water systems have limited exchange surface surface and thus need very high temperatures to do anything?
  - mikeyouse 4y ago
    Yep - exactly the issue. They've started shipping much more efficient baseboard systems which run at lower temps by adding more fins, adding CPU fans to increase heat transfer across the plates, etc. but the correct answer is to usually invest in air sealing/insulating the house which will require fewer BTUs in the first place.
- WatchdogReset 4y ago
  I think this is possible. I will ask to a teacher of hvac-learning and come back to you asap. But basically you can heat water instead of air with a heat pump.
- WatchdogReset 4y ago
  As others comments said, it depends on the climate : The problem is that the power/performance of the heat pumps decreases with the cold weather and the necessary increase in the temperature of the heating water, which obliges to keep the boiler for the cold weather. This is a problem for the heat pumps without probable solution and little progress to wait. The solution is to insulate the house very well so that its needs can be covered by the heat pump with less hot water. Divide the losses by 2 at least.

mastermedo 4y ago

I'm getting an error when trying to load the page: > Error establishing a database connection https://web.archive.org/web/20230210134443/https://hvac-learning.com/courses/heat-pumps-part-1/ https://web.archive.org/web/20230210134443/https://hvac-lear... The archive.org is pretty slow on this one as well, as it is an interactive site.

Neil44 4y ago
OOM Killer strikes again - it always loves mysqld for some reason...
- WatchdogReset 4y ago
  If you have advice for me, I'll take it ;) can exchange with HVAC courses
WatchdogReset 4y ago
The website is new and not fit yet for such numbers of visit, so sometimes it does not render well pages. I(admin) still in the process of understanding how to build a nice website. I will analyze what happened and enhance it. I'm sorry for the inconvenience !

deleted 4y ago

[deleted]

yreg 4y ago

Technology Connections has a good video on heat pumps. (Actually several of them, I link the newest one.) https://www.youtube.com/watch?v=MFEHFsO-XSI https://www.youtube.com/watch?v=MFEHFsO-XSI

generaltsos 4y ago
That channel is fascinating. They have created some incredibly interesting projects.
- manigandham 4y ago
  What have they created? You might be thinking of Tech Ingredients - https://www.youtube.com/@TechIngredients https://www.youtube.com/@TechIngredients
  - generaltsos 4y ago
    You're spot on - I am subscribed to both so I confused them without opening any links. Technology Connections is fascinating in its own right as well.
pkulak 4y ago
I just found this guy too. He answered a lot of questions I had about efficiency and use below freezing. https://youtu.be/fxEqVuiHhM0 https://youtu.be/fxEqVuiHhM0
- kenmacd 4y ago
  I like his videos, but I don't trust his numbers in this one. He shows a COP of ~1 when it's 10 degrees out. These are the easiest possible conditions for the HP, and where all the specs show the highest COP. His graph showing the HP is running equal to a baseboard heater seems very suspect.
  - pkulak 4y ago

boringg 4y ago

What is going on? Is there a global push to get everyone to switch to heat pumps. It seems that there is heat pump content everywhere. Clearly there is a push. I understand that its for climate benefits but it feels very coordinated. edit: didn't realize the attention I would get. Let me add someone answered my question -- a good product market fit and people talking is probably where the push came from. That said HVAC installers / heat pump manufacturers and governments are all pushing this hard right now. I believe in the benefit for most people and the climate benefits are great. I am always concerned on when there is large consensus on a hard push - worth looking at who the winners are and what the trade offs are.

nashashmi 4y ago
Heat pumps are the opposite of AC. AC industry is behind this for sure. It is like a paid PR campaign. It is not more economical then gas. So now gas is going to be punished for factors X,Y,Z. It is coordinated. I wish there is more investigative research into who and why they are doing this.
- WatchdogReset 4y ago
  For the record, I am only trying to make my elearning website more known. There is plenty of other HVAC subject that I would like to share. It's just that Heat Pump where for me an interesting topics to get into the subject but you can have a look at other free courses.
- mikeyouse 4y ago
  Ah yes, "big AC" is bullying the Oil and Gas industry with their subversive marketing. If only Exxon, BP, and Shell had some political clout they could expose this plot.
- jamiek88 4y ago
  In this thread you’ve gone form ‘compressors don’t work like that’ to ‘this is all a conspiracy by big A/C’. You are not engaging with any of the helpful, generous replies, in fact going as far as to say that you wish you could call it ‘coordinated’. Why are you even here if you think we are all lying shill for big air compressor?

beardyw 4y ago

Error establishing a database connection

WatchdogReset 4y ago
The site is pretty new, I(admin) am not used to have lots of traffic. I will analyze what happened and chose better solution. I am sorry for the inconvenience !

Bhilai 4y ago

Definitely a lot of posts about heat pumps on HN recently that this topic has piqued my interest but only to the point that I want to know if I can install one in my home. Are there any legit resources out there that can help me understand if heat pump is a right choice for my home based on Geo, type of home, sqft and other factors to consider before replacing current systems (two ACs and two furnaces?)

hcknwscommenter 4y ago
My $0.02 are that any competent and honest HVAC company will be able to walk you through the concepts of your home's heating/cooling load etc. and what size heat pump can meet that need, what it costs to run annually, and what incentives there are. It's not that hard. I would reach out to three highly ranked (or word of mouth suggested) HVAC co's and start the conversation.
rapsey 4y ago
I guess they are a new thing in the US. In Europe installing a heat pump with floor heating is done for practically every new family house. It is the cheapest (for us) and nicest way to heat up your home. Though very few people build houses out of wood, unlike the US.
- gautamcgoel 4y ago
  What are the houses usually made of? Stone?
  - rapsey 4y ago
    Engineering/perforated bricks mostly. North Germany/UK is a lot of solid red/gray bricks, not sure if new homes still use that style, since it has terrible insulation. If built with perforated bricks a home will also put a thick layer of styrofoam for insulation on the outside.
gwbas1c 4y ago
Generally, they can work anywhere in the continental US. (Assuming you live in the US.) If you're in northern NH, NY, VT, or Maine, you might want to keep your gas system as a backup. (New homes tend to have electric backup, but if you have an older home they just keep your furnace as backup.) I have a 3000 sqft house in MA with a heat pump as my primary heat, and an electric strip as backup. The heat pump goes into the ductwork for most of the house. I generally haven't had problems. (It did have to be adjusted because it was the first time the installer put one in.) I have solar and usually get 1-2 large bills in January and February, and then March and April are very cheap, if I get a bill at all. My "large" January and February are comparable to what I'd spend on conventional heat. Last weekend we had a "once in a century" cold snap down to -4. Most of the house was at temp, but one room fell to the high 50s. From what I've heard, plenty of people with conventional heat had far worse issues than a chilly room.

kebman 4y ago

Looks like the HN posting crashed the site.

WatchdogReset 4y ago
The site is pretty new, I am the webmaster, maybe I should analyze the log and choose better hosting. I am sorry about the inconvenience!
- kebman 4y ago
  No worries, I'll take a look at your site later. :) If it helps, I tried reaching the site from Norway. Thanks for reaching out! Edit: It works just fine now! Looks pretty interesting!

asow92 4y ago

As someone who lives in the northeast and has a 3600sqft home, I'm wondering how many heat pumps it would take to replace my gas steam boiler system. I'm not sure if heat pumps would be cost efficient given those parameters.

prottog 4y ago
In the Northeast with that much square footage, you would be better off with ground-source heat pumps (whether open or closed loop), rather than the normal air-source heat pumps.
- asow92 4y ago
  I guess the concern I have with all this is that my current system works well, and I don't want to spend $10K+ unless it brings down my heating costs significantly. Could a ground-source heat pump system do that?
  - zeroonetwothree 4y ago
    It depends on relative prices in your area so we can’t answer that. You would have to calculate it yourself. Typically it makes the most sense to do when you need to replace your system.
  - sbradford26 4y ago
    Ground source/geothermal would significantly reduce your heating costs but it would be significantly more than 10k. For that large of house something like 40k+ wouldn't be out of the question, with the largest expense being drilling. I personally think geothermal is great, sadly New England's geography makes getting a ground loop installed more difficult. In the midwest lots of people would do a horizontal loop by trenching like 8 feet underground laying pipe in there. In many parts of new england that isn't really viable with all the rock so vertical drilling is used which is significantly more expensive.
    - snuxoll 4y ago

chem83 4y ago

I’ve had Mitsubishi heat pumps in a condo in the northeast for 3 years and they’ve worked great. No other heating sources here. I keep them on all day, which the mfgt discourages. My main gripe was their kumo cloud and Wi-Fi connectivity but they’ve since fixed firmware and the cloud side and it works much better.

YellowTech 4y ago

Seems like OP just performed a stress test on his website as he is the "Webmaster of https://hvac-learning.com https://hvac-learning.com an HVAC elearning website"[1]. Hopefully you can figure out something! Thank you for educating about such technology! [1] from WatchdogReset's profile about

WatchdogReset 4y ago
I am sorry for the inconvenience. I am still learning how to build a nice and efficient website. I will analyze what happened and try to fix and enhance !
- scrollaway 4y ago
  I love that you're building free educational resources, especially about something like this! If you need help/advice to help build your website, email me (see my profile), I'll be delighted to help pro bono. :)

endisneigh 4y ago

I wish, wish wish there was a portable mini split (not a portable air conditioner). The closest thing is this: https://rollibot.com/product/mini-split-ac-room-air-conditioner/ https://rollibot.com/product/mini-split-ac-room-air-conditio... but it sucks. I don't understand why these things have to be permanent fixtures of your house, necessarily.

bilsbie 4y ago
I’m confused what you’re asking for (and why) but it sounds interesting.
- endisneigh 4y ago
  A portable machine to provide heat and cooling via heat pump technology. For cooling this exists in many forms: there are the window air conditioners, and "portable" window air conditioners which have a duct that connects to the window. The problem with the latter is that they're loud and the ducts result in a lot of heat loss. For heating there are some portable air conditioners that use a heat pump but they're subject to the same issue described above. More common is resistive electrical heat in the form of coils or an oil filled container that radiates heat. A portable mini split, where it connects through the window would give you a similar advantage as a portable air conditioner, but with more efficiency and being less loud.
  - bilsbie 4y ago
    Cool idea. So a two piece portable with a just coolant line going through the window to the outdoor part?
    - endisneigh 4y ago
      yeah, exactly. there's a company called MRCOOL that does something similar (https://mrcool.com/diy-4th-generation/ https://mrcool.com/diy-4th-generation/), but the head (the indoor part that provides the heat/cooling) is designed to be mounted permanently if this were popular you'd see old houses retrofitted with pluggable holes where you could feed the lineset through and seal as necessary for temporary heat/cooling, or perhaps even permanent. the installation would be substantially easier if these were like 6000BTU instead of minimum 12000BTU per head, so it could be run on say, ~8 amps and be plugged inside.

rr888 4y ago

I just dont like moving parts. My problem with heat pumps is that you have to replace every 10-20 years which seems wasteful.

kupopuffs 4y ago
Do you own a heater that has lasted more than 10 years?
- bluGill 4y ago
  The furnace in my house is from 1970 and still works. I don't want to know how inefficient it is. (I just upgraded the insulation of the house, replacing the furnace is a future problem)
timbit42 4y ago
My heat pump has a CoP of 3 and paid for itself in 10 years. New heat pumps have a CoP of 4 or higher and might pay for themselves in less. How much material in a heat pump is recyclable and how much isn't, compared to a furnace? We are trying to reduce CO2 and methane in the atmosphere. Throwing away the non-recyclable parts of heat pumps isn't as big of a concern. Polluting the ground and water isn't even as big a concern. Certainly they are concerns, but they pale in comparison.

boringg 4y ago

Oh I have a question for the community here about heat pumps. I have three mini splits that I use for AC but connecting them to a home hub is bananas amount of work and inconsistent (Mitsubishi brand). I wish there was a legitimately good, robust system to connect AC units to my smart thermostat (Ecobee) or even some of the other devices I have. It still feels the wild west for home energy systems - and the costs are quite high for the value they provide.

mataug 4y ago
So far I've been happy with using the mysa ecosystem for my smart home. It works with Apple HomeKit, its had relatively good reliability and the team behind the product have been responsive when I do face issues. https://shop-us.getmysa.com/products/mysa-ac https://shop-us.getmysa.com/products/mysa-ac From a technical perspective its just a IR remote with a wifi connection and a touch UI, but for controlling mini-splits it works great in my home.

spikej 4y ago

Genuine question that I haven't been able to find a clear answer for: are heat pumps now different from air conditioners two to three decades ago? (other than the fact that they heat and cool) Memory is fuzzy but I remember when I was a little kid and even captain planet cartoon showed air conditioners being bad for the environment... Or is it that heat pumps are better than the fossil fuel counterparts and so if you're going to do something bad you might as well do something less bad?

Calvin02 4y ago
It is the latter. Heat pumps are much better for the environment compared to the other sources of heating. Depending on where you live, you still need to heat your place and if so, heat pumps are better than other traditional methods like natural gas, wood, oil, or electricity. Similar to air conditioning, if you want to minimize your impact on the climate, you could set your temperature lower in the winter and put on a few more layers and/or set the temperature higher in the summer to minimize your usage of heat pump/air conditioner. This puts less pressure on the grid and demand for electricity generation.
bagels 4y ago
Captain Planet is not a reliable source of information. Air conditioners use electricity, the generation of which can cause fossil fuels, but also can come from other sources.
ccooffee 4y ago
> even captain planet cartoon showed air conditioners being bad for the environment That seems like it was a useful simplification for a children's cartoon, but things aren't that black-and-white. 1. Without air conditioning (or some other method of cooling and humidity control), almost all high-occupancy buildings would reduce their effectiveness as a work-place or living-place. OSHA has guidelines about office temperature (68-76, iirc), humidity, and overall air quality (e.g. pm2.5 levels). 2. The 1980s-era backlash against air conditioning was likely inspired by then-new knowledge about atmospheric ozone depletion. It was known that CFCs and bromine-containing compounds contribute to ozone depletion. It just so happens that CFC were common refrigerants (and aerosolizing agents). Refrigerant leaks from an air conditioner in those times released nasty stuff. CFCs are very rare (and restricted) in modern air conditioner / hvac systems. We instead use other chemicals which are not ozone depleters. (Though I believe that the theoretical performance of modern refrigerants is often not-as-good as the old CFCs.) 3. Running the air conditioner in a single family home is not terribly efficient, as (in most single family homes) most of the home is just empty space. Cooling bodies directly (e.g. cooling blankets, misting fans, etc) is more energy-efficient in these situations. Perhaps the more nuanced advice would be to use air conditioning to make the space "tolerable" but use direct cooling to make a space "comfortable". (This advice also applies to heating a space. I keep my thermostat between 60 and 65 and use blankets, small electrical resistance heaters, and drinking hot water as ways to temperature-regulate.)

energ8 4y ago

I have seen repeated claims of heat pump CoPs improving over decades. Can anyone summarize or provide links to what improvements are being made? Compressor technology? refrigerants? Fans to move heat? all of the above? Where is the path from here?

LazyMans 4y ago
I can provide a likely incomplete summary of the improvements. Compressors themselves have gotten much more energy efficient, although I'm not sure the impact on CoP is all that great since and waste heat from the compressor is being deposited in the home anyway. Variable speed compressors are the most efficient you can get pretty much. Refrigerants have improved in someways, but not really in others. Since heat pumps could be running with exterior temperatures that are quite low, with the system under pressure, some refrigerant blends would have less than desirable vapor pressures leading to problems running in very low temperature conditions. For the most part, the changes to refrigerant blends have been related to their Global Warming Potential (GWP). Expansion valves are a very important piece of a refrigerant loop, these used to be fixed orifaces. Nowadays these are dynamic, meaning they can increase efficiency of the system by metering the flow based on system load and other characteristics. These are called TXVs or Thermostatic Expansion Valves. Electronically controlled expansion valves are now hitting the market further increasing efficiency. Finally there is the design of the interior and exterior coils. I dont think materials have changed much, but the surface area has changed. You may noticed a 2 ton unit from 1997 is about 1/4th the size of a 2 ton unit from 2022. More surface area on the coil for the exterior unit lets you extract more heat from the air without burning a ton of energy running the fan super hard. Interior air handlers have probably improved some as well, variable speed motors, etc. Variable speed really is nice because you can get much more consistent temperatures in the home and wont get blasted in the face with heat from vents when a regular system cycles on and off.
Freestyler_3 4y ago
refrigerants (though some regulations have negative impact on this), Optimizing (DC motors and computers with sensors figuring out what is the best setting), Absorbing waste heat from the process, Insulation, Materials that stay more clean or self clean.

molsongolden 4y ago

Calvin (Segment) and Baker (Plaid) also recently put together a nice up-to-date heat pump info page and a heat pump vs. existing HVAC calculator. https://heatpumpshooray.com/ https://heatpumpshooray.com/ https://calv.info/heat-pumps https://calv.info/heat-pumps

raldi 4y ago
What do you mean by Segment and Plaid?
- kaveet 4y ago
  Calvin French-Owen is the founder of Segment and Baker Shogry was Head of Product at Plaid until recently.

hbarka 4y ago

It's worth mentioning that there are many heat pump makers now using CO2 as the refrigerant versus the older environmentally harmful ones.

vladgur 4y ago

I live in SF Bay Area 20 minutes south of SF and I don’t have and don’t need A/C, so my HVAC needs are met by a gas furnace that is 10-15 years old at this point but it still works. Another caveat is our electricity ranges from 30 to 35 cents per KWh and is probably second to Hawaii in terms of cost. So I do check the cost of operating a Heatpump in the winter and due to high cost of power I am sticking with our gas furnace. If and when I go solar, I may reconsider, but for now gas is simply cheaper

ericpauley 4y ago
As high as that is, it looks like the price of gas in SF is (relatively) even higher. $4.50 a therm per Google, or $0.15/kWh. A heat pump would only need a COP of 35/15=2.33 to be a better deal (very likely since it will never be that cold in SF, and you get air conditioning for the very few days you might want it).
stavros 4y ago
As the Technology Connections video linked here mentions, "if it’s more expensive to use the option that saves energy... that’s a problem".
liminalsunset 4y ago
TL;DR a heat pump isn't worth it in Vancouver, BC, for me anyway. As a counterpoint to what seems to me like extremely high rates for electricity, as of right now in Vancouver, BC, Canada, I recently calculated that a heat pump would cost about ~2.5-3.5 cents per kWh of heat energy vs ~4.5 cents for gas heating at 80% efficiency. Power on average is about $0.10 USD per kWh here and gas is about $10 USD per GJ. The average house here uses 74.3 GJ of gas per year, or $ 743 USD of gas. We would save 413 $ per year by switching over. The neighbours next door spent $ 17000 USD to install a multi-zone heat pump, which still doesn't exactly cover every room. It's a Samsung, so by the general sentiment about their appliances here, we'll assume it doesn't last longer than 15 years and needs to be replaced at a cost of 12000 $ USD down the line. The hot water, low efficiency 80% boiler has lasted 35 years so far. Total cost of maintenance and repairs has been under $1500 USD. We expect it to last another 30 years easily because there is absolutely nothing special, fragile, or expensive in this system. Most of the spare parts can be found by walking down the alley and seeing which neighbour fell for the "replace your heating system" salesman tactics. If we replaced it with a "high efficiency" condensing type, we would save at most 20% on our gas bill (143 USD a year). The cost to install will be easily $5000. As a reward for doing so, we will have to pay for maintenance every 5 years at $200, and the device will fail and need to be replaced for another $4000 after 15 years. This is a statistical and practical certainty because condensate is corrosive. For the next 30 years, the old boiler we have will cost 23790 USD in total. Upgrading to a high efficiency boiler will cost us $28032 USD in total, not including ANY breakdowns Using a heat pump will cost $38900 USD in total, not including any maintenance, which you ABSOLUTELY need to do otherwise it smells and grows mould. (we do this maintenance ourselves but the design of the unit is ghastly, I curse the designer out loud every time I think of it, and this is a MAJOR pain to do.) Based on this math, there is absolutely no reason we would ever consider making any of these changes. A plumber tried to suggest something like this and they seemed to agree. With this said, I have a heat pump in my room, originally installed because I had too many computers and I needed air conditioning. We bought the absolute cheapest unit we could find at 700 USD and it has been wonderful. It has a capillary tube instead of an EXV because it's cheap, but it works "fine" down to -5 and it rarely goes under that here. The greatest benefit of a heat pump has nothing to do with energy efficiency or savings. The greatest benefit is that every room can have their own heating and cooling controls that respond FAST. I turn it up and down all the time when I feel like it and it's wonderful.

vladgur 4y ago

Is there a good calculator where I can enter my cost for units of electricity and gas and it will tell me how much operating a heat pump will save me over a gas furnace

timbit42 4y ago
To get a useful answer, you would have to put in more information. How many floors? How many sq ft per floor, what is the R value of your house? How cold can it get in the winter? How often is it that cold? Are you asking about air-to-air or ground-source heat pumps? The best thing to do is to get one or more local installers to give you an estimate.

billiam 4y ago

The other issue here in SF and near the coast is that for older, poorly insulated homes and those with high ceilings (mine are 12 feet), the real problem with an air heat pump is how slow it is to heat the volume. Unless you want to pay to keep your house warm 24-7 it will take an hour to warm up the whole house. I would love to kick my 10 year old forced air gas furnace to the curb, but I don't see how, even if I get solar. Contractors are charging a fortune for installing heat pumps these days too.

fragmede 4y ago
But, at 3x the efficiency of a traditional gas furnace, it may still be cheaper to heat the house all day, or have it start heating at 4:30 pm.
timbit42 4y ago
Heat pumps aren't meant to be turned on and off. In fact, they aren't meant to have the thermostat changed either, even at night. You set it to what you want and it keeps it there. Once it gets the temp where you set it, it doesn't use much electricity to keep it there unless it is very cold, like below freezing and especially below -20C. Due to your high ceilings, it might be prudent to install ceiling fans to help circulate the heat, but I'm not a heating expert so I recommend asking one.

kerpotgh 4y ago

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