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Show HN: Heat Pumps, Hooray – A heat pump calculator for your home

40 points by calvinfo 4y ago

bake 4y ago
Hi HN -- We’re Baker and Calvin, two heat pump nerds who are really excited about home electrification and its impact on climate change. During our explorations, we realized really struggled to find good calculators out there for understanding the impacts a heat pump can have on your specific home. So… we built one! It’s free to use, and we’re curious to get your feedback. Feel free to try it out here, and let us know what you think!
- drx 4y ago
  This is awesome! Must have been a lot of work.
  - bake 4y ago
    Thank you so much! It was a truly great learning experience, and definitely more to go.
    - sokoloff 4y ago
      On iOS at least, expanded ducts are showing as $15 (despite adding the more reasonable $15K to the total). Similarly, a panel upgrade is listed as “$1,000 to $3” despite adding the (slightly light) $1K-$3K to the upfront expense summary. Rotating the display to landscape shows the full numbers, so it’s a styling issue, not a content issue. I was hoping to see an air-to-water calculator as hydronic heat is common in New England. If that equipment wasn’t so premium-priced and hard to find experienced installers, I think a lot of conversions could happen.
      - bake 4y ago
        Roger that! We're hearing the desire for hydronic / air-to-water systems and support for Europe / elsewhere from a few different places, so this is helpful. Note for those in Europe, we're using local energy prices and local grid emissions in addition to local weather, so we'd need to expand those to cover additional geos as well. And thanks for catching the issue on mobile, we'll get that fixed asap.
- mrguyorama 4y ago
  From the "calculator" the default "heat to" temp is 68. That seems kind of absurd to call a default indoor air temperature during winter months. Is used for all day or just night time temps?
  - mwint 4y ago
    This is about what we do in our house. Is it absurdly high or low?
    - mrguyorama 4y ago
      It's very low for a daytime temperature. Maybe it makes sense with the gas crunch and energy prices in europe, but the specific thing that bothers me about it is hiding that number below the "advanced" checkbox. I don't think people who are used to paying for winter time heating set their thermostat to 68, so using that number to calculate how much a heat pump costs to run will artificially lower the cost of the heat pump in this calculator.
      - bake 4y ago
        I'll take a look back at the residential energy consumption survey and the exact distributions. The Manual J (industry standard approach to load sizing) uses 70 dF for heating and 75 dF for cooling as its defaults, so we could definitely update the defaults to those, too.
      - callalex 4y ago
        Even in warm sunny California I don’t know a single person who sets their heater above 70°.
      - athorax 4y ago
        I'm in Colorado and have the furnace set between 63-65 in the winter by choice, nothing to do with cost
      - stevenhubertron 4y ago
        I also live in CO and have it at 64 at night and 68 during day. Very comfortable.
- vba616 4y ago
  It doesn't seem like the chart of costs includes the effect of summer A/C. And the chart that is shown peaks in winter a couple months early. Overall, it seems to significantly underestimate my energy costs. The conclusion is also confusing: it says I would save $89/year or $24K in 15 years. Huh? $89/year doesn't seem like enough to justify any investment, and $24K is about $1600/year or ~95% of my current costs, which seems too high to believe.
  - bake 4y ago
    This is really good feedback, thank you -- the "$24k" number is something we're going back to the drawing board on, we're reaching too much there. That number includes the capital costs of replacing and installing equipment (a single heat pump vs. both a furnace and an A/C unit, for example, plus rebates), and it's best case for heat pumps vs. worst case for legacy equipment. So, I think you're right, it just doesn't line up sensibly with the really concrete annual energy savings numbers. On winter peaks, I'll have to look into what you're seeing -- we pull weather data from the nearest ASOS station to your zip code and have done a fair bit of validation on that data, but it could be a number of things. If you're interested, you could send the inputs you're using to pumpers@heatpumpshooray.com and I'll do a little digging?
  - bake 4y ago
    FYI, we just updated that section of the results to hopefully be clearer and, when it comes to the total lifetime savings including equipment costs, a bit more conservative.
- deleted 4y ago
  [deleted]
Siecje 4y ago
Great job! This has a lot of information without making the UI overwhelming. I have a bug report I got "1.5e+2% of your annual heating."
- bake 4y ago
  Aha, thank you!!
sparrish 4y ago
"Switching to a heat pump, you'll save $67.53 per year" also "Total savings over a 15-year period are up to $37,000" I must be missing something cause that doesn't add up.
- calvinfo 4y ago
  Thanks for giving it a try! We've tried to make this a little clearer in the "receipt view", but the major difference is in terms of cost of the hardware. Furnaces, heat pumps, and A/C units all have a 15-20 year useful lifetime. While the annual savings will be only a bit less, the hardware cost will be _significantly_ less because you only need a one unit for a heat pump vs two for an A/C + furnace combo. Does that make more sense? We'll try and clarify in the UI
  - ars 4y ago
    If you already have an A/C a furnace is very very cheap, so cheap it's almost free (i.e. included with the A/C). I don't see how you can possibly save $37,000 just by getting rid of the furnace - they just don't cost that much.
woutgaze 4y ago
Does anyone know something similar for Europeans (I live in The Netherlands)? Common units used here are all metric; for heating I've seen Natural Gas Usage (in m3) used and GigaJoules. Also almost no-one here seems to use air conditioning.
- bake 4y ago
  I'd suggest asking the folks at https://lun.energy https://lun.energy, to start. You're right that our site doesn't yet work for homes outside of the US, unfortunately. The approach would be similar, but some different equipment and home configurations to consider along with different data sets (fuel pricing, weather, grid emissions, etc.) -- I'll keep an eye out for good resources, and would love to help anyone who wants to try to build it!
  - pjc50 4y ago
    Interesting site, although once you go deeper than the front page it's in Swedish.
- Glawen 4y ago
  In Europe we have water based heating system, be it radiator or floor heating. That changes the equation quite a bit, and also impact what type of heat pump you can install (low temp or mid temp). The best is to have a hybrid system: a heat pump and a gas/oil/wood boiler which will fire up when it is freezing.
  - pjc50 4y ago
    I'm .. suspicious of hybrid systems. I've encountered a company which was pushing them, and I don't like the idea that I'll be paying gas standing charge and installation cost for a very rarely used boiler.
    - bake 4y ago
      I am as well. I started out my own journey convinced that we should keep our existing high-efficiency gas furnaces for backup heat, but when we finally did the math, it would have saved us a whopping $3 over the last twelve months vs. using electric resistive backup, and that was using last year's cheaper gas prices... In the US, if you need backup heating (and you may not, with the heat pumps that are on the. market today), electric resistive heating (heat strips/coils) is indeed more expensive than high-efficiency gas furnaces BTU-for-BTU, but remember that resistive heating runs in parallel with the heat pumps, whereas furnaces have to take over entirely for dual fuel systems. Natural gas might be cheaper than electric resistance alone, but electric resistance plus the heat pump even at diminished capacity can be a very different story.
ars 4y ago
I'm not sure it's doing the right thing when I entered a multi-zone mini-split. It's acting like I'm buying a separate A/C for each zone, but that's not how they are priced. I have 9 for "Heat pump: Number of units", and 2 for "AC equipment: Number of units ". Also it's having trouble doing the math right because I have window A/C, but I would get a mini-split for A/C and Cooling. For me the math is just not right - if I put in a mini-split to have A/C, I need to decide what's cheaper, running my high efficiency boiler (that I already have), vs heating using the heat pump. That's really all I want to know: What costs less, heat with gas, or heat with electricity. Or maybe a hybrid. This seems geared more to people who have existing ducted A/C with a furnace (not a boiler), who might get rid of the boiler part, and leave the rest. (Or just not use the boiler.) IMO you should just stick to calculate fuel costs for heat with gas, vs heat with electricity, and leave out the installation costs.
- bake 4y ago
  This is helpful -- we need to do a better job of guiding folks through a more complex set-up like you're describing. You're right that it's easiest for folks with centrally ducted A/C and furnaces. If you're choosing 'multi-zone', "Heat pump: Number of units" corresponds to the number of _outdoor_ units, rather than indoor heads. For all other configurations, it maps to both outdoor and indoor (the others are all single zone). So, if you want to go with a multi-zone heat pump, I'd suggest entering 1 or 2 for "Heat pump: Number of units" (or just leaving it untouched, in which case the model will choose automatically based on home size). > IMO you should just stick to calculate fuel costs for heat with gas, vs heat with electricity, and leave out the installation costs. Roger that. We started out that way, and the cost-to-install was the number one thing that people asked us in follow-up questions, so we added some high-level guidance. I think the lack of transparency on upfront costs and pricing is a major issue for the transition broadly and a problem that needs to be solved -- that's high on our minds. > That's really all I want to know: What costs less, heat with gas, or heat with electricity. Or maybe a hybrid. Helpful! Related to the previous point, we want to make it easier for you, with a proposal from a contractor in hand or existing equipment already installed, to choose that equipment from among what we're analyzing (rather than only seeing cost savings for the most efficient unit that we choose automatically). In your case, you'd then be able to see exactly the cutoff points when your existing fossil fuel equipment is (a) necessary because of reduced heat pump capacity at lower temperatures, or (b) cheaper to run than the heat pump. FWIW, (b) is far rarer than we thought going into this exercise.
mig39 4y ago
Put in the zip code for Fairbanks, Alaska. 99701. Not so good :-( I guess heat pumps aren't great when it's really really cold?
- calvinfo 4y ago
  The colder it gets, the lower the efficiency. In a more extreme climate like Fairbanks, the efficiency pretty much drops down to resistive heating (1.0). If you're set on electrifying there, it might make more sense to investigate a ground-source heat pump which leverages the ambient underground temperature for heat exchange.
  - bake 4y ago
    Big plus to ground-source here! Everything shown on the site today is air-source only.
- bake 4y ago
  There are definitely still places in the U.S. where air-source heat pumps aren't economical. That said, two big things for most folks to keep in mind: 1. Air-source heat pumps are getting better and better, quickly, so that answer is changing 2. 93% of US homeowners would save money with air-source heat pumps vs. their existing equipment, and only 3% of homes would see an annual utility bill increase above $70. (these from backtesting the national sample of homes from the EIA's RECS survey) A lot of people think "really really cold" means it hits zero a few times each winter. They don't know what living in Fairbanks is like :), and chances are that heat pumps can keep up with their local weather.
  - vba616 4y ago
    >A lot of people think "really really cold" means it hits zero a few times each winter See this seems to me an illustration of something being hinky about the discussion. "Hits zero a few times each winter" quite possibly is an accurate description of the climate where I live. I believe only one month had a below zero low recorded last winter. But representing my climate with that particular factoid would gloss over that lows around freezing down to subzero are typical for like six months of the year, and the other six months, you don't need heat in the first place. A lot of people in the CONUS really do live where winter is pretty harsh, not just North Dakota or something. The important thing for saving on energy bills, which I don't ever see brought up in any online discussion about heat pumps, is how bimodal the climate is, not how extreme the winter lows are. I can't say there is nowhere in the world where the temperature graaaaaaadually ramps up and down all year. But all I see is people taking for granted that's how it works and thus heat pumps spend a large amount of time in the optimal range.
benj111 4y ago
The sliders labelled basic are slightly confusing, especially as it's dimmed suggesting 'basic' is off. Maybe a down arrow and advanced? Also as a non USian without a zip code, this is fairly useless to me.
- bake 4y ago
  Thanks for the feedback! We can make those sliders better, thanks for the suggestions. Yes, unfortunately we haven't seen great resources for the rest of the world, either. The same approach and core model here would work elsewhere, but we'll need to source historical data on housing stock, residential energy prices, grid emissions, weather to get it up and running elsewhere. If you know anyone that would be interested in taking that on, definitely let us know!
Projectiboga 4y ago
Fyi you will still need a backup heat source as heat pumps have a lower temperature limit to where they can't capture heat from out side that is around freezing to 20 degrees fahrenheit.
- teruakohatu 4y ago
  Modern heatpumps can go far lower than that. Many mitsibushi sold in my country can operate at -15 Celsius. I think the newest from mitsibushi can do -20 C. Efficiency does decrease since they need to spend more time defrosting.
  - 8fingerlouie 4y ago
    My 2022 Vaillant model can operate down to -25C, and has a backup electrical heating element built in for when it gets colder than that. https://www.vaillant.com/home/products/air-to-water-heat-pump-system-arotherm-plus-12096.html https://www.vaillant.com/home/products/air-to-water-heat-pum...
- bake 4y ago
  You may or may not need backup heat, it depends on your particular home. Heat pumps DO still capture heat below freezing and down to temperatures much, much lower than they used to. Mitsubishi, for example, sells air source heat pumps that maintain 100% heating capacity down to 5 dF and can still heat (albeit at reduced capacity) down to -13 dF: https://www.mitsubishicomfort.com/articles/keep-warm-this-winter-inverter-technology-for-any-climate https://www.mitsubishicomfort.com/articles/keep-warm-this-wi... We model decreasing heat pump capacity and efficiency as the outside air temperature declines. Yes, heat pumps do lose capacity and efficiency the colder it gets, but they can still provide heat even when it's very cold out (there's heat energy in the air until absolute zero, or -273, after all!). You can see that declining efficiency if you expand the "Step 2: Choosing your ideal heat pump" section. We'll add a graph of capacity relative to outside air temperature as well. Backup heat is still often necessary for many homes in cold climates, but it's necessary a lot less often than you might think. Note that in the results you'll see for the site, backup heat is included if necessary for single-zone centrally ducted heat pumps, but not for any other ducting types.
rainbowzootsuit 4y ago
I would suggest that folks interested in energy efficiency improvement take a spin with NREL's BEopt software. It allows you to make a simple 3D model of your home, enter its current state of construction (insulation, HVAC system, roof, solar panels, etc.), and then uses the DOE's energy plus (e+) software to run energy analysis for different scenarios of modification to the building. For example you can find the optimal balance between improvement to your insulation vs getting a more efficient HVAC system in terms of dollars or energy usage, depending on your goals for your home. https://www.nrel.gov/buildings/beopt.html https://www.nrel.gov/buildings/beopt.html
- bake 4y ago
  Great suggestion -- HPH was a stab at making more sophisticated tools like that more approachable for homeowners, but for folks able and inclined to use the more powerful software out there (including energy plus and open studio), it could be really useful. One thing we've built but not yet included in the site is a way to back into a more precise heating/cooling load for the home using past utility bills. That could be useful even for folks going down the more bottoms-up modeling route as a way to help with the 'garbage in / garbage out' problem of having to estimate insulation, window heat transfer, etc. etc.
Dork1234 4y ago
It seems like it takes a long time to process/calculate the simulation. Is this done server side? Is there a reason for the slowness?
- bake 4y ago
  Hi! Yes, the simulation is all server-side. It does take a while today -- we aren't using the beefiest machines for the site, but even locally it's a >5s process. Some of the things driving speed: - Fetching hourly weather data -- we use binned data for the 15-30 years used for equipment sizing and selection, but for the 12 month backtest to get savings and emissions, we're going hour by hour through the last year for the simulation. - Loading + merging emissions data -- same deal for hourly grid emissions for your local grid, to get emissions from electricity usage (though we do make some assumptions about the grid decarbonizing when we show expected lifetime emissions figures). - Simulating thermostat behavior -- we do some extra processing before the core simulation to model realistic human behavior on thermostat setting, so that you don't get lots of flipping between heat+cool in shoulder months or the furnace kicking on in June just because it hits 68dF in the middle of the night. - Heat pump equipment selection -- we're doing a slightly simplified version of the backtest over 15-30 years of historical data for ~2k heat pump units (depending on ducting type) as a bake-off to choose the most efficient-but-properly-sized heat pump for the home. There's more optimization to be done there, but it's about 2-3s of the total time currently. - Backtest itself -- once we have the equipment chosen and the weather + thermostat scenarios created, we run the simulation itself for the last 12 months, twice (once for the status quo equipment, once for the heat pump configuration). That goes through each hour of the year, simulating heat load on the home (outside weather including cloud cover and solar positioning, humidity, wind speed, temperature, plus internal loads like appliances and the heat occupants give off), simulating equipment performance (for heat pumps, a function of output, outside temp, inside temp, outside humidity, altitude, and layering in backup heat as applicable/needed), plus accounting for surplus/deficit heat that needs to roll over to the next hour based on thermostat settings or insufficient conditioning, etc. etc.. With usage, we then compile and calculate the utility bills monthly (we have support for actual rate plans, TOU plans, etc., but for now we just use statewide marginal retail prices from the EIA for the site version, because those tend to be conservative) and also calculate emissions, which is time intensive for electricity given we're layering in actual emissions from the grid in the simulated hour. Anyways, there's definitely a lot of optimization we could do to get the processing time down, but hope that gives you a sense of what's going on server-side. Also, the model we're running is more flexible than what's exposed on the site currently (e.g. arbitrary date ranges for the backtest), and if we made a more specialized version of it, we could do a lot more pre-computing.
8fingerlouie 4y ago
I'm a european (with a heat pump), but i tried it anyway. I entered : - Zip 56714 - 2500 sqft - 4 occupants - 1 boiler - no aircon - natural gas and the result was : Switching to a heat pump will increase your cost by... $257.28 per year So i'm not entirely sure it works as you intended, or natural gas is much cheaper than electricity. Over here, Natural gas is currently at €2.96/m3 (about 2.5x the price last year), and every calculation we've made based on the heat pump vs natual gas shows it will reduce our annual bill by about 50%. I've had the heat pump for 6 months, and while it was spring/summer with reduced need for heating, the total consumption of the heat pump in those 6 months has been around 900 kWh, and i estimate around 2000 kWh for the winter. (2000 sqft house, well insulated compared to US standards)
- bake 4y ago
  Hi! Yes, couple of primary things that would drive that answer: 1/ Right now, if you select "No A/C", we still include the cost+emissions of cooling from the heat pump. It's on the backlog to add a "heat vs. heat only" comparison. In part, we're assuming that if you have cooling capability, you'll probably use it (and therefore wanted to include that in the emissions impact), but also that homes without A/C today will have small cooling loads to begin with, so it wouldn't change the answer too dramatically. For now, I'd suggest looking at the monthly costs in the summer on the bar chart and mentally adjusting the headline number for those. Sorry that's not smoother! 2/ Natural gas is indeed way cheaper here -- dramatically so this year, but previously as well. The backtest shown on the site is Feb '21 to Feb '22 -- natural gas prices this coming winter are bound to be much higher than they were last year, so savings numbers will definitely change going forward. It's on our list to (a) make that dynamic clearer on the site, and (b) explore a more forward-looking savings number. Right now, the annual energy costs are "what you would have saved _last year_ vs. your existing equipment", instead of what you might expect, thinking that would be more convincing / less controversial, albeit potentially conservative. Thrilled to hear you're 6mo into life with a heat pump! Is it air-to-water and still using water/steam radiators, or forced air now?
  - 8fingerlouie 4y ago
    > Thrilled to hear you're 6mo into life with a heat pump! It was the logical thing to do. Even before the war in Ukraine, the ROI of the heat pump was 8-10 years compared to natural gas. With current conditions, shortage of natural gas, inflation and more, the ROI is around 4 years. > Is it air-to-water and still using water/steam radiators, or forced air now? Pretty much everything regarding heat in (northern) Europe is based on water, with the exception of hotels that usually use either only air or a combination of air/water. Our particular installation is from the 1970s, meaning it's 1 string and made for much higher flow temperatures than the houses from 2000 and onwards, so instead of a 35C flow temperature we instead have a 55C flow temperature, which reduces the COP value of the heat pump. My particular model (https://www.vaillant.com/home/products/air-to-water-heat-pump-system-arotherm-plus-12096.html#specification https://www.vaillant.com/home/products/air-to-water-heat-pum...) has a COP value of (up to) 5.4 with a flow temperature of 35C, which gets reduced to around 4 with a 55C flow temperature. I've coupled mine with radiator thermostats from Tado (https://www.tado.com/gb-en/products https://www.tado.com/gb-en/products) which use geofencing to lower the temperature when nobody is home, and they also have a "sensor/control unit" for the heat pump control itself, allowing fine grained control of the heat pump. One of their upcoming features is to try to optimize heat pump usage for when electricity is cheap.
gs17 4y ago
Am I misreading it? How can I save more than 100% of my annual heating/cooling costs each year?

40 points by calvinfo 4y ago

bake 4y ago

Hi HN -- We’re Baker and Calvin, two heat pump nerds who are really excited about home electrification and its impact on climate change. During our explorations, we realized really struggled to find good calculators out there for understanding the impacts a heat pump can have on your specific home. So… we built one! It’s free to use, and we’re curious to get your feedback. Feel free to try it out here, and let us know what you think!

drx 4y ago
This is awesome! Must have been a lot of work.
- bake 4y ago
  Thank you so much! It was a truly great learning experience, and definitely more to go.
  - sokoloff 4y ago
    On iOS at least, expanded ducts are showing as $15 (despite adding the more reasonable $15K to the total). Similarly, a panel upgrade is listed as “$1,000 to $3” despite adding the (slightly light) $1K-$3K to the upfront expense summary. Rotating the display to landscape shows the full numbers, so it’s a styling issue, not a content issue. I was hoping to see an air-to-water calculator as hydronic heat is common in New England. If that equipment wasn’t so premium-priced and hard to find experienced installers, I think a lot of conversions could happen.
    - bake 4y ago
      Roger that! We're hearing the desire for hydronic / air-to-water systems and support for Europe / elsewhere from a few different places, so this is helpful. Note for those in Europe, we're using local energy prices and local grid emissions in addition to local weather, so we'd need to expand those to cover additional geos as well. And thanks for catching the issue on mobile, we'll get that fixed asap.
mrguyorama 4y ago
From the "calculator" the default "heat to" temp is 68. That seems kind of absurd to call a default indoor air temperature during winter months. Is used for all day or just night time temps?
- mwint 4y ago
  This is about what we do in our house. Is it absurdly high or low?
  - mrguyorama 4y ago
    It's very low for a daytime temperature. Maybe it makes sense with the gas crunch and energy prices in europe, but the specific thing that bothers me about it is hiding that number below the "advanced" checkbox. I don't think people who are used to paying for winter time heating set their thermostat to 68, so using that number to calculate how much a heat pump costs to run will artificially lower the cost of the heat pump in this calculator.
    - bake 4y ago
      I'll take a look back at the residential energy consumption survey and the exact distributions. The Manual J (industry standard approach to load sizing) uses 70 dF for heating and 75 dF for cooling as its defaults, so we could definitely update the defaults to those, too.
    - callalex 4y ago
      Even in warm sunny California I don’t know a single person who sets their heater above 70°.
    - athorax 4y ago
      I'm in Colorado and have the furnace set between 63-65 in the winter by choice, nothing to do with cost
    - stevenhubertron 4y ago
      I also live in CO and have it at 64 at night and 68 during day. Very comfortable.
vba616 4y ago
It doesn't seem like the chart of costs includes the effect of summer A/C. And the chart that is shown peaks in winter a couple months early. Overall, it seems to significantly underestimate my energy costs. The conclusion is also confusing: it says I would save $89/year or $24K in 15 years. Huh? $89/year doesn't seem like enough to justify any investment, and $24K is about $1600/year or ~95% of my current costs, which seems too high to believe.
- bake 4y ago
  This is really good feedback, thank you -- the "$24k" number is something we're going back to the drawing board on, we're reaching too much there. That number includes the capital costs of replacing and installing equipment (a single heat pump vs. both a furnace and an A/C unit, for example, plus rebates), and it's best case for heat pumps vs. worst case for legacy equipment. So, I think you're right, it just doesn't line up sensibly with the really concrete annual energy savings numbers. On winter peaks, I'll have to look into what you're seeing -- we pull weather data from the nearest ASOS station to your zip code and have done a fair bit of validation on that data, but it could be a number of things. If you're interested, you could send the inputs you're using to pumpers@heatpumpshooray.com and I'll do a little digging?
- bake 4y ago
  FYI, we just updated that section of the results to hopefully be clearer and, when it comes to the total lifetime savings including equipment costs, a bit more conservative.
deleted 4y ago
[deleted]

Siecje 4y ago

Great job! This has a lot of information without making the UI overwhelming. I have a bug report I got "1.5e+2% of your annual heating."

bake 4y ago
Aha, thank you!!

sparrish 4y ago

"Switching to a heat pump, you'll save $67.53 per year" also "Total savings over a 15-year period are up to $37,000" I must be missing something cause that doesn't add up.

calvinfo 4y ago
Thanks for giving it a try! We've tried to make this a little clearer in the "receipt view", but the major difference is in terms of cost of the hardware. Furnaces, heat pumps, and A/C units all have a 15-20 year useful lifetime. While the annual savings will be only a bit less, the hardware cost will be _significantly_ less because you only need a one unit for a heat pump vs two for an A/C + furnace combo. Does that make more sense? We'll try and clarify in the UI
- ars 4y ago
  If you already have an A/C a furnace is very very cheap, so cheap it's almost free (i.e. included with the A/C). I don't see how you can possibly save $37,000 just by getting rid of the furnace - they just don't cost that much.

woutgaze 4y ago

Does anyone know something similar for Europeans (I live in The Netherlands)? Common units used here are all metric; for heating I've seen Natural Gas Usage (in m3) used and GigaJoules. Also almost no-one here seems to use air conditioning.

bake 4y ago
I'd suggest asking the folks at https://lun.energy https://lun.energy, to start. You're right that our site doesn't yet work for homes outside of the US, unfortunately. The approach would be similar, but some different equipment and home configurations to consider along with different data sets (fuel pricing, weather, grid emissions, etc.) -- I'll keep an eye out for good resources, and would love to help anyone who wants to try to build it!
- pjc50 4y ago
  Interesting site, although once you go deeper than the front page it's in Swedish.
Glawen 4y ago
In Europe we have water based heating system, be it radiator or floor heating. That changes the equation quite a bit, and also impact what type of heat pump you can install (low temp or mid temp). The best is to have a hybrid system: a heat pump and a gas/oil/wood boiler which will fire up when it is freezing.
- pjc50 4y ago
  I'm .. suspicious of hybrid systems. I've encountered a company which was pushing them, and I don't like the idea that I'll be paying gas standing charge and installation cost for a very rarely used boiler.
  - bake 4y ago
    I am as well. I started out my own journey convinced that we should keep our existing high-efficiency gas furnaces for backup heat, but when we finally did the math, it would have saved us a whopping $3 over the last twelve months vs. using electric resistive backup, and that was using last year's cheaper gas prices... In the US, if you need backup heating (and you may not, with the heat pumps that are on the. market today), electric resistive heating (heat strips/coils) is indeed more expensive than high-efficiency gas furnaces BTU-for-BTU, but remember that resistive heating runs in parallel with the heat pumps, whereas furnaces have to take over entirely for dual fuel systems. Natural gas might be cheaper than electric resistance alone, but electric resistance plus the heat pump even at diminished capacity can be a very different story.

ars 4y ago

I'm not sure it's doing the right thing when I entered a multi-zone mini-split. It's acting like I'm buying a separate A/C for each zone, but that's not how they are priced. I have 9 for "Heat pump: Number of units", and 2 for "AC equipment: Number of units ". Also it's having trouble doing the math right because I have window A/C, but I would get a mini-split for A/C and Cooling. For me the math is just not right - if I put in a mini-split to have A/C, I need to decide what's cheaper, running my high efficiency boiler (that I already have), vs heating using the heat pump. That's really all I want to know: What costs less, heat with gas, or heat with electricity. Or maybe a hybrid. This seems geared more to people who have existing ducted A/C with a furnace (not a boiler), who might get rid of the boiler part, and leave the rest. (Or just not use the boiler.) IMO you should just stick to calculate fuel costs for heat with gas, vs heat with electricity, and leave out the installation costs.

bake 4y ago
This is helpful -- we need to do a better job of guiding folks through a more complex set-up like you're describing. You're right that it's easiest for folks with centrally ducted A/C and furnaces. If you're choosing 'multi-zone', "Heat pump: Number of units" corresponds to the number of _outdoor_ units, rather than indoor heads. For all other configurations, it maps to both outdoor and indoor (the others are all single zone). So, if you want to go with a multi-zone heat pump, I'd suggest entering 1 or 2 for "Heat pump: Number of units" (or just leaving it untouched, in which case the model will choose automatically based on home size). > IMO you should just stick to calculate fuel costs for heat with gas, vs heat with electricity, and leave out the installation costs. Roger that. We started out that way, and the cost-to-install was the number one thing that people asked us in follow-up questions, so we added some high-level guidance. I think the lack of transparency on upfront costs and pricing is a major issue for the transition broadly and a problem that needs to be solved -- that's high on our minds. > That's really all I want to know: What costs less, heat with gas, or heat with electricity. Or maybe a hybrid. Helpful! Related to the previous point, we want to make it easier for you, with a proposal from a contractor in hand or existing equipment already installed, to choose that equipment from among what we're analyzing (rather than only seeing cost savings for the most efficient unit that we choose automatically). In your case, you'd then be able to see exactly the cutoff points when your existing fossil fuel equipment is (a) necessary because of reduced heat pump capacity at lower temperatures, or (b) cheaper to run than the heat pump. FWIW, (b) is far rarer than we thought going into this exercise.

mig39 4y ago

Put in the zip code for Fairbanks, Alaska. 99701. Not so good :-( I guess heat pumps aren't great when it's really really cold?

calvinfo 4y ago
The colder it gets, the lower the efficiency. In a more extreme climate like Fairbanks, the efficiency pretty much drops down to resistive heating (1.0). If you're set on electrifying there, it might make more sense to investigate a ground-source heat pump which leverages the ambient underground temperature for heat exchange.
- bake 4y ago
  Big plus to ground-source here! Everything shown on the site today is air-source only.
bake 4y ago
There are definitely still places in the U.S. where air-source heat pumps aren't economical. That said, two big things for most folks to keep in mind: 1. Air-source heat pumps are getting better and better, quickly, so that answer is changing 2. 93% of US homeowners would save money with air-source heat pumps vs. their existing equipment, and only 3% of homes would see an annual utility bill increase above $70. (these from backtesting the national sample of homes from the EIA's RECS survey) A lot of people think "really really cold" means it hits zero a few times each winter. They don't know what living in Fairbanks is like :), and chances are that heat pumps can keep up with their local weather.
- vba616 4y ago
  >A lot of people think "really really cold" means it hits zero a few times each winter See this seems to me an illustration of something being hinky about the discussion. "Hits zero a few times each winter" quite possibly is an accurate description of the climate where I live. I believe only one month had a below zero low recorded last winter. But representing my climate with that particular factoid would gloss over that lows around freezing down to subzero are typical for like six months of the year, and the other six months, you don't need heat in the first place. A lot of people in the CONUS really do live where winter is pretty harsh, not just North Dakota or something. The important thing for saving on energy bills, which I don't ever see brought up in any online discussion about heat pumps, is how bimodal the climate is, not how extreme the winter lows are. I can't say there is nowhere in the world where the temperature graaaaaaadually ramps up and down all year. But all I see is people taking for granted that's how it works and thus heat pumps spend a large amount of time in the optimal range.

benj111 4y ago

The sliders labelled basic are slightly confusing, especially as it's dimmed suggesting 'basic' is off. Maybe a down arrow and advanced? Also as a non USian without a zip code, this is fairly useless to me.

bake 4y ago
Thanks for the feedback! We can make those sliders better, thanks for the suggestions. Yes, unfortunately we haven't seen great resources for the rest of the world, either. The same approach and core model here would work elsewhere, but we'll need to source historical data on housing stock, residential energy prices, grid emissions, weather to get it up and running elsewhere. If you know anyone that would be interested in taking that on, definitely let us know!

Projectiboga 4y ago

Fyi you will still need a backup heat source as heat pumps have a lower temperature limit to where they can't capture heat from out side that is around freezing to 20 degrees fahrenheit.

teruakohatu 4y ago
Modern heatpumps can go far lower than that. Many mitsibushi sold in my country can operate at -15 Celsius. I think the newest from mitsibushi can do -20 C. Efficiency does decrease since they need to spend more time defrosting.
- 8fingerlouie 4y ago
  My 2022 Vaillant model can operate down to -25C, and has a backup electrical heating element built in for when it gets colder than that. https://www.vaillant.com/home/products/air-to-water-heat-pump-system-arotherm-plus-12096.html https://www.vaillant.com/home/products/air-to-water-heat-pum...
bake 4y ago
You may or may not need backup heat, it depends on your particular home. Heat pumps DO still capture heat below freezing and down to temperatures much, much lower than they used to. Mitsubishi, for example, sells air source heat pumps that maintain 100% heating capacity down to 5 dF and can still heat (albeit at reduced capacity) down to -13 dF: https://www.mitsubishicomfort.com/articles/keep-warm-this-winter-inverter-technology-for-any-climate https://www.mitsubishicomfort.com/articles/keep-warm-this-wi... We model decreasing heat pump capacity and efficiency as the outside air temperature declines. Yes, heat pumps do lose capacity and efficiency the colder it gets, but they can still provide heat even when it's very cold out (there's heat energy in the air until absolute zero, or -273, after all!). You can see that declining efficiency if you expand the "Step 2: Choosing your ideal heat pump" section. We'll add a graph of capacity relative to outside air temperature as well. Backup heat is still often necessary for many homes in cold climates, but it's necessary a lot less often than you might think. Note that in the results you'll see for the site, backup heat is included if necessary for single-zone centrally ducted heat pumps, but not for any other ducting types.

rainbowzootsuit 4y ago

I would suggest that folks interested in energy efficiency improvement take a spin with NREL's BEopt software. It allows you to make a simple 3D model of your home, enter its current state of construction (insulation, HVAC system, roof, solar panels, etc.), and then uses the DOE's energy plus (e+) software to run energy analysis for different scenarios of modification to the building. For example you can find the optimal balance between improvement to your insulation vs getting a more efficient HVAC system in terms of dollars or energy usage, depending on your goals for your home. https://www.nrel.gov/buildings/beopt.html https://www.nrel.gov/buildings/beopt.html

bake 4y ago
Great suggestion -- HPH was a stab at making more sophisticated tools like that more approachable for homeowners, but for folks able and inclined to use the more powerful software out there (including energy plus and open studio), it could be really useful. One thing we've built but not yet included in the site is a way to back into a more precise heating/cooling load for the home using past utility bills. That could be useful even for folks going down the more bottoms-up modeling route as a way to help with the 'garbage in / garbage out' problem of having to estimate insulation, window heat transfer, etc. etc.

Dork1234 4y ago

It seems like it takes a long time to process/calculate the simulation. Is this done server side? Is there a reason for the slowness?

bake 4y ago
Hi! Yes, the simulation is all server-side. It does take a while today -- we aren't using the beefiest machines for the site, but even locally it's a >5s process. Some of the things driving speed: - Fetching hourly weather data -- we use binned data for the 15-30 years used for equipment sizing and selection, but for the 12 month backtest to get savings and emissions, we're going hour by hour through the last year for the simulation. - Loading + merging emissions data -- same deal for hourly grid emissions for your local grid, to get emissions from electricity usage (though we do make some assumptions about the grid decarbonizing when we show expected lifetime emissions figures). - Simulating thermostat behavior -- we do some extra processing before the core simulation to model realistic human behavior on thermostat setting, so that you don't get lots of flipping between heat+cool in shoulder months or the furnace kicking on in June just because it hits 68dF in the middle of the night. - Heat pump equipment selection -- we're doing a slightly simplified version of the backtest over 15-30 years of historical data for ~2k heat pump units (depending on ducting type) as a bake-off to choose the most efficient-but-properly-sized heat pump for the home. There's more optimization to be done there, but it's about 2-3s of the total time currently. - Backtest itself -- once we have the equipment chosen and the weather + thermostat scenarios created, we run the simulation itself for the last 12 months, twice (once for the status quo equipment, once for the heat pump configuration). That goes through each hour of the year, simulating heat load on the home (outside weather including cloud cover and solar positioning, humidity, wind speed, temperature, plus internal loads like appliances and the heat occupants give off), simulating equipment performance (for heat pumps, a function of output, outside temp, inside temp, outside humidity, altitude, and layering in backup heat as applicable/needed), plus accounting for surplus/deficit heat that needs to roll over to the next hour based on thermostat settings or insufficient conditioning, etc. etc.. With usage, we then compile and calculate the utility bills monthly (we have support for actual rate plans, TOU plans, etc., but for now we just use statewide marginal retail prices from the EIA for the site version, because those tend to be conservative) and also calculate emissions, which is time intensive for electricity given we're layering in actual emissions from the grid in the simulated hour. Anyways, there's definitely a lot of optimization we could do to get the processing time down, but hope that gives you a sense of what's going on server-side. Also, the model we're running is more flexible than what's exposed on the site currently (e.g. arbitrary date ranges for the backtest), and if we made a more specialized version of it, we could do a lot more pre-computing.

8fingerlouie 4y ago

I'm a european (with a heat pump), but i tried it anyway. I entered : - Zip 56714 - 2500 sqft - 4 occupants - 1 boiler - no aircon - natural gas and the result was : Switching to a heat pump will increase your cost by... $257.28 per year So i'm not entirely sure it works as you intended, or natural gas is much cheaper than electricity. Over here, Natural gas is currently at €2.96/m3 (about 2.5x the price last year), and every calculation we've made based on the heat pump vs natual gas shows it will reduce our annual bill by about 50%. I've had the heat pump for 6 months, and while it was spring/summer with reduced need for heating, the total consumption of the heat pump in those 6 months has been around 900 kWh, and i estimate around 2000 kWh for the winter. (2000 sqft house, well insulated compared to US standards)

bake 4y ago
Hi! Yes, couple of primary things that would drive that answer: 1/ Right now, if you select "No A/C", we still include the cost+emissions of cooling from the heat pump. It's on the backlog to add a "heat vs. heat only" comparison. In part, we're assuming that if you have cooling capability, you'll probably use it (and therefore wanted to include that in the emissions impact), but also that homes without A/C today will have small cooling loads to begin with, so it wouldn't change the answer too dramatically. For now, I'd suggest looking at the monthly costs in the summer on the bar chart and mentally adjusting the headline number for those. Sorry that's not smoother! 2/ Natural gas is indeed way cheaper here -- dramatically so this year, but previously as well. The backtest shown on the site is Feb '21 to Feb '22 -- natural gas prices this coming winter are bound to be much higher than they were last year, so savings numbers will definitely change going forward. It's on our list to (a) make that dynamic clearer on the site, and (b) explore a more forward-looking savings number. Right now, the annual energy costs are "what you would have saved _last year_ vs. your existing equipment", instead of what you might expect, thinking that would be more convincing / less controversial, albeit potentially conservative. Thrilled to hear you're 6mo into life with a heat pump! Is it air-to-water and still using water/steam radiators, or forced air now?
- 8fingerlouie 4y ago
  > Thrilled to hear you're 6mo into life with a heat pump! It was the logical thing to do. Even before the war in Ukraine, the ROI of the heat pump was 8-10 years compared to natural gas. With current conditions, shortage of natural gas, inflation and more, the ROI is around 4 years. > Is it air-to-water and still using water/steam radiators, or forced air now? Pretty much everything regarding heat in (northern) Europe is based on water, with the exception of hotels that usually use either only air or a combination of air/water. Our particular installation is from the 1970s, meaning it's 1 string and made for much higher flow temperatures than the houses from 2000 and onwards, so instead of a 35C flow temperature we instead have a 55C flow temperature, which reduces the COP value of the heat pump. My particular model (https://www.vaillant.com/home/products/air-to-water-heat-pump-system-arotherm-plus-12096.html#specification https://www.vaillant.com/home/products/air-to-water-heat-pum...) has a COP value of (up to) 5.4 with a flow temperature of 35C, which gets reduced to around 4 with a 55C flow temperature. I've coupled mine with radiator thermostats from Tado (https://www.tado.com/gb-en/products https://www.tado.com/gb-en/products) which use geofencing to lower the temperature when nobody is home, and they also have a "sensor/control unit" for the heat pump control itself, allowing fine grained control of the heat pump. One of their upcoming features is to try to optimize heat pump usage for when electricity is cheap.

gs17 4y ago

Am I misreading it? How can I save more than 100% of my annual heating/cooling costs each year?