You and the planet need a heat pump
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I don't understand why there's been so much brouhaha over heat pumps as of late, it's nothing new.
It is something new for the mainstream American consumer.
They just didn't call it a heat pump, but it's a heat pump. This is just marketing bullshit AFAICT.
Every electric engine is a generator.
Every speaker is a microphone.
Means nothing, because they suck in these unintended applications unless they were specifically designed for them.
What changed recently is - heat pumps and solar panels got cheap/good enough to be viable alternative for heating houses in most climates.
You have used several analogous relations to show a larger pattern. You've extracted the utility and distilled it into its essence. It's really hard to stretch what you wrote too far until it breaks, like most standalone analogies. Love it!
(Commenting here in the hope that more people will adopt the tactic.)
Industry vernacular: Air conditioner / air con: Unidirectional. Cools home. air cooled. Furnace or heater: Separate unit to provide heat in home. Furnace is gas, heater is electric. Heat pump: Bidirectional. Can heat or cool home. air cooled. Also, can come with "emergency heat" electric heaters. Ground source or geothermal heat pump: Bidirectional. can heat or cool home. water cooled. Swamp cooler: evaporative cooler.
It's an incredibly misleading terminology to use.
I have a neighbor who last year replaced their small window AC unit in their off-grid desert cabin with what they described as a "heat pump" window unit after being convinced it was a more energy efficient solution for cooling their cabin with their limited solar array.
Unsurprisingly it made zero difference because they replaced an existing heat pump with basically the same thing under a different name. Waste of money, not the brightest individual, but the marketing push of new whiz-bang efficient heat pumps falling from the heavens is strong.
In fact many heat pumps aren't reversible because replacing a coal stove heating a traditional water pipes and radiators system - with a reversible heat pump - will mess up your house when water condenses inside walls around the cold pipes. The whole system needs to be designed for this.
Also heat pumps are designed differently depending on the climate and operating temperature ranges. So buying a heat pump without asking someone to do the math is very risky and stupid. And probably it breaks the building code.
It's a f*cking window unit emblazoned with "heat pump" marketing exploiting this ambiguous terminology. All air conditioners are heat pumps, this whole situation is stupid.
I'm not sure I agree with that statement. Living in a hot climate, I've had heat pumps on every house I've lived in for 40+ years here. It's really not even a realistic option to not have one. They are essential in humidity control as well as temperature control.
The coefficient of power of a decent heat pump is much higher than two, so the dollar cost of powering a heat pump is much lower than that of natural gas, down to some crazy temperature, like -15F.
Also air source heat pumps that out perform ground source pumps have recently become commonplace, and mini-splits make for easy retrofits in response to climate change.
The (b) heat pump option is more expensive up front, but over the course of 10 years (minimum expected life of the heat pump) worked out the same as (a) natural gas, and has the added benefit of being able to cool the house in the summer.
Once you take into account solar (which was calculated to pay itself off after 6 years) it makes no financial sense to choose natural gas. I made these calculations in 2019 and used a rather optimistic 2.5% inflation rate for energy prices, so if you do that again today it's even more in favour of the heat pump and solar.
(I am aware that there are gas absorption heat pumps, but there are very few manufacturers right now, and the ones I found available here were 2-3x the price of an electric unit)
Lots of houses here used to be heated using resistive, electric radiators, through the 70s-90s. Now most of those houses are primarily heated using heat pumps.
Mitsubishi is the most recommended manufacturer by local heat pump aficionados - yes, there kinda is such a thing...
Swedish language forum: https://www.varmepumpsforum.com/vpforum/index.php?action=for...
Technically not correct. A heat pump does not pump air in/out of a building. It pumps a refrigerant around in a closed loop. Part of this loop is inside and part is outside.
When used for heating, the efficiency of a heat pump system declines as the outside temperature drops. At a temperature of around 32F, a heat pump essentially becomes useless. As a result, most have an auxiliary fallback heat source.
Additionally, for proper efficiency the key components of the system need to be sized for your target temperature and the temperature range of your ambient air.
Don't confuse the two.
The efficiency of a home heat pump declines as the air temperature outside the home drops. A freezer is working in reverse so it's efficiency declines as the air temperature outside the freezer box rises.
Neither a heat pump in an Alaskan winter nor a freezer sitting on a Florida back porch in summer are operating very efficiently.
Now, the original claim of "heat pumps don't work below freezing" is trivially wrong (and so the question by lasson was justified), but the overall point is that heat pump efficiency gets worse the more you need it in the case of keeping your home warm.
Invalid assumption.
Whether it can or not depends on the environment.
Most ordinary freezers are designed to operate within a relatively luxurious temperature controlled in-door environment. Stick one in the sun on a Florida back porch in August and you may well discover it can no longer successfully "extract energy from the side that is below freezing". Same thing (only in reverse) can happen with a home heat pump in an Alaskan winter.
There is another important element here --- energy loss and insulation.
At a certain temperature (whatever it may be), the energy lost to the surroundings will start to exceed the capacity of the heat pump. At some point; speaking in practical terms, the heat pump becomes essentially worthless. You need either a bigger heat pump or you need more insulation to stop the loss --- both of which cost money and can't be obtained/installed immediately.
The heat pump dramatically decreased my power bill vs baseboard electric.
https://www.researchgate.net/figure/e-efficiency-of-an-Air-S...
Are you referring to resistive heating?
That very much depends on the cost of your electricity and fuel. In MA, where I pay about $0.20/kWh and around $1.60/therm (both delivered), natural gas is around 2/3rds the cost of a heat pump in the coldest months (and loses only slightly in the shoulder months, when the heat pump is more efficient but you don’t have as much heat loss).
Here are lab test results for some of the most efficient heat pumps on the market: https://www.nrel.gov/docs/fy11osti/52175.pdf
Below 25F the heat pump is more expensive. At 35F it is cheaper. (Page 10)
Natural gas would be about 2/3 cheaper at 5F.
There are "hybrid heat pumps" that might make more sense in your climate. They use resistive or natural gas below a certain temperature. I'm not sure which "side" of the compressor they heat.
No I'm not; I'm literally looking at my last gas bill right now. I'm paying $0.8309/therm for gas and $0.8945 for delivery services. That's $1.7254/therm, not $5.80/therm. (At $5.80/therm, I’d have upgraded a decade ago [or switched the house back to #2 fuel oil]!)
At 85% efficiency, that's $20.30 per million BTU for gas. *
Looking at the only maker of split-system air-to-water heat pumps in the North American market, their spec sheet COP** at 120ºF leaving water temperature is 3.33 at 45º outside air, 2.86 at 35ºF, 2.42 at 25ºF, and 1.99 at 15ºF. For February, that looks like I'd expect a BTU-weighted COP of around 2.5-2.6.
All from a system that would cost me around $15K additional out-of-pocket (after incentives) and would save a few hundred bucks in the shoulder season and cost me a couple hundred extra across Jan and Feb. $15K and less comfort on the coldest days to save $100 per year is a pretty negative RoI. $15K invested in Treasuries has a higher (and more certain) return and is liquid at the end, not thrown away.
* https://www.amsenergy.com/fuel-cost-calculator/
** https://www.nordicghp.com/wp-content/uploads/2021/10/001850S... (I selected the split-system here because it avoids the efficiency and temperature losses from a glycol-to-water plate heat exchanger that the monobloc units would entail. I need every degree of leaving water temperature that I can muster as I determined experimentally that my house is able to be comfortable down to 12º outside air temp at a boiler LWT of 130ºF on 1st and 2nd floor, but needed 145ºF in the attic [so would need to have the emitters [currently finned baseboard] replaced if I could only muster 120-125ºF LWT].) Spacepak is coming out with a split ASHP sometime soon, but has no technical literature published yet and I'm not going to be the first in the nation... :D
I studied the crap out of this, because I was hopeful that with $10K of incentives on the table that this could be close enough to make the switch worthwhile and eliminate on-site burning of fossil fuels in the house. It seems like we’re not there yet and there’s no guarantee that electricity will inflate at a pace slower than natural gas over the next 20 years, so this could get better or worse. Maybe the only supplier goes belly-up. Maybe something better comes along and no one wants to buy a house with this weirdo system in it. Parts would probably not be in stock at the nearest two supply houses. Only a few plumbers could work on it. In a scenario with that many unknowns, dropping in a $3K combi that everyone knows how to work on and parts are on the shelf 10 minutes away for $3-5K out of pocket (after factoring the almost $3K incentive on a high efficiency gas boiler) is a way better play and then see what comes along 10 years from now at the boiler mid-life or 20 years from now when it’s due for replacement.
You can use that number when looking at a heat pump's datasheet to see which temperatures the heat pump would be cost effective for you.
For me my electric rates are pretty high, and my gas rates are pretty lowso in the winter I doubt a heat pump would be cheaper, in the fall and early spring when you just need to raise maybe 10deg over outside sure, but in the deep of winter I doubt it
The system works fine and my best guess is that it is somewhere around 3:1 in favour of heat pump over resistive heat (electric baseboard or radiant panels).
That would mean a COP of 3.
Sadly, all this is immensely expensive AND takes a few decades to financially amortize. Which means for people with lower incomes, who would benefit the most from this, still have to burn money to stay warm. :/
Over here it is actually pretty common, it's currently a huge pain to find contractors (plus they're getting more expensive by the day). We talked to a lot of people who about what they did, and I have two findings: 1. Sustainability (of materials) is usually a lesser factor, most people seem to care most about the energy saving and to some extent the improved comfort. 2. Most people do these improvements over a long time, e.g. do the roof when they can afford it, save some money (or pay off the loan) and do the windows,... - so that might take up to a decade to get the house up to a decent standard. Doing "all at once" is more rare, and those people are surprised when we tell them we plan to do as much as possible early on, as we can then earlier realize the potential savings.
btw, I envy your draftfree house ^^"
Loungerooms with no doors, so the split system on the wall has to work 3x as hard to cool half the bloody house.
Ducted heating/cooling without any valves, so your choices are either "heat up every room in the house", "get up on a step ladder to close off each vent manually" or "be cold".
Cheaping out on insulation to knock a grand or two off of your million dollar new build.
Just like in the software world, I suspect we'd be able to make massive efficiency gains just by actually engaging our brains. No special technology required, nor specialist knowledge. Just think about things for two seconds before putting in the semi-permanent installations.
The material costs were rounding error. I can't even remember what the increase was.
The builders might have been saving you from yourself there, actually. I know at least one "acoustic" insulation product on the market (worked on by my old man before the mass layoffs at CSR/Bradford) isn't actually better at noise reduction than other products (funnily enough, it was measurably worse than some of the other, more expensive batts); just they've specced it as such and advertised it on the packaging.
They're a little pricey but might be worth it if you have a large house or if you care more about energy efficiency than upfront cost.
Here's one type: https://www.amazon.com/Zone-Damper-Round-Professional-Grade-...
For total control you would need 1 of those for every vent in the house, plus wiring, installation, and a controller for it all, so it would be a few grand at least, but if you had a few rooms that had issues with hot-spotting or cold-spotting and controlling the temps evenly were difficult, it might be a good option for you.
You could also try something like this: https://www.amazon.com/Flair-Compatible-Honeywell-thermostat... and the relevant temperature sensing pucks to do the same thing for a few rooms easily.
Whereas they didn't have a choice previously, they'll now have the choice between using energy and sweating, which will likely increase energy usage in summer. OTOH, sunny days will likely have plenty of energy available due to solar, and it will avoid inefficient workarounds like mono units (air conditioners where the hot side is cooled with room air that is then exhausted through a hose typically stuck through a poorly sealed window - it's as inefficient and annoying as it sounds, but often the best you can do in a rented apartment in Europe).
Even with a $10K rebate, it's far more cost-effective to go with a modern gas boiler (which has its own $2750 rebate) and I have no worries of ~72 hours/year of being unable to maintain temperature. (That's not that big of a worry for me and wouldn't be a blocker, but it's a small inconvenience.)
Basically, the heating contractors know the rebate amounts and, unsurprisingly, bake that into their bids. I can't really blame them for following the incentives, but it means that the energy-savings incentives don't have the intended effect.
However, there are sometimes (often?) alternatives in which the utility banks excess production and trades it during times of low production on a 1:1 basis. I have not read that this sort of scheme faces the same sort of opposition from utilities (and some legislators) as "cash for kW".
This is great for apartment dwellers / condos / low income areas, because you can structure the finances of the initial investment to look a lot like having the individual/business installing the equipment being paid retail for the surplus power.
If I went that route, I'd install a brand new small boiler (or more likely an electric resistance boiler). It wouldn't take much to take that concern entirely off the table. 30K BTU/hr (9kW) would do it, a 9kW electric boiler is cheap to buy (~$1200), and on the 3 days a year where it would be used, it would have a COP of 1.0 while the heat pump would have a COP of probably 1.5-1.6, so you're not giving up that much efficiency to make it a decision driver. Then, you also have emergency backup heat if the heat pump is temporarily down as well.
I'd be surprised if these boilers do not.
https://www.nordicghp.com/wp-content/uploads/2021/10/001850S...
Basically the installers didn’t bother with a torque wrench and just hand tightened all the connectors. The broke every single one, and the install company would only replace one at a time.. then it would leak.. then they replaced another etc.
I understand the issues with very cold temperatures, and I'm curious what proportion of American households would expect to see outside temperatures below -17C/0F - I doubt it would be enough to explain the reluctance but I could be way wrong.
Modern air source heat pump systems (e.g. Daikin Altherma) are quiet due to variable speed compressors, work in heat pump mode down to -25C and have built in backup heat if it goes below that.
They are even more efficient than electric ones.
What if there were a centralized temperature control distribution hub and pump, so you only needed one for the house that would serve all of these applications?
At a high level the article is correct. At a tactical level there are a few issues:
* If you don't have a "geothermal" system, heat pumps aren't economical in regions where it gets below 0F/-20C.
* There is a 20 year depreciation cycle for furnaces, and it doesn't make sense to install them at a significantly faster rate.
* You lose a lot of the efficiency benefits when the electricity is generated from burning fossil fuels elsewhere. And we are nowhere near having enough electricity from solar and wind to heat houses in the wintertime.
* I only know the numbers for germany, where even in new buildings there are a lot of fossil furnaces getting installed still. Replacements in older houses also usually don't switch to a heat pumps, pushing both numbers >80% would already be a major achievement in my book.
You haven't defined economical but here's a quote from Mitsubishi:
"Hyper-Heating INVERTER® (H2i®) technology which can provide up to 100 percent of heating capacity at 5° F and continue operation down to -13° F even without auxiliary heat. Select units equipped with Mitsubishi Electric’s H2i plus™ technology can deliver up to 100 percent heating capacity down to -5° F"
Efficiency is always measured relative to something and cannot be over 100% in a closed system, heat pumps are not a closed system so no laws of physics are broken.
It's one of those sufficiently advanced technologies that seems like magic. Like, what if we powered a sufficiently efficient sterling engine with it, and used that to spin the compressor and fans?
It's not obvious that it isn't a perpetual motion machine or some commercially available version of Maxwell's demon or something.
The heat in the atmosphere, is also due to some energy consumed somewhere, whether man made or not.
It would be like saying your gas boiler is 10000% efficient because of how little electricity it uses.
What you are using as fuel is the heat in the outside air.
- efficiency is related also to /flow/ temperature. Which is much lower than the gas boiler it might replace - so you need big emitters (large radiators, Under-floor-heating) - and good insulation
What might make 100% sense in a new build where you can design for these factors, but be awful in many existing homes.
I'd like to see if I'm really saving energy (and money) doing this. And how long the payback period is for buying new equipment.
Of course space heaters are far easier to move around the house compared to a mini-split system and would use less power if you only plan to heat a small room.
* https://www.mitsubishielectric.ca/en/hvac/professionals/fs-s...
* https://www.mitsubishicomfort.com/articles/what-is-a-heat-pu...
* https://www.fujitsu-general.com/us/residential/benefits/year...
Some folks using them in Alaska:
* https://www.nrel.gov/news/features/2021/even-in-frigid-tempe...
If you get a heat pump that looks like the 'traditional' external AC unit (giant cube), those tend to work down to about +5C. Not sure how much more they cost above a 'regular' air conditioner:
* https://www.lennox.com/products/heating-cooling/heat-pumps
The Technology Connections channel has a couple of interesting videos on the topic of heat pumps:
* https://www.youtube.com/watch?v=7J52mDjZzto
* https://www.youtube.com/watch?v=7zrx-b2sLUs
He has a video entitled "How to calculate when heat pumps make financial sense (and other heat pump follow-up thoughts)":
* https://www.youtube.com/watch?v=BRdq2ExLJns
NR Canada has a "AIR-SOURCE HEAT PUMP SIZING AND SELECTION GUIDE":
* https://www.nrcan.gc.ca/sites/nrcan/files/canmetenergy/pdf/A...
Financially speaking you're going to have to break out a spreadsheet and plug numbers in: (natural) gas prices, electricity prices, efficiency of the units, etc. Doing a search for "heat pump calculator" may get you started.
https://www.nrel.gov/docs/fy11osti/52175.pdf
I walk through the "what's the break even temperature" elsewhere in this thread (where I pasted the same URL).
Also, it is kind of a moot point. If you're putting in central air (not a minisplit), it will probably automatically fall back to natural gas or resistive if it gets too cold outside. (Too cold should be something like -5F or less, assuming it falls back to resistive.)
I ended up going with air-source heat pumps rather than geothermal. The geothermal units were less expensive, but the drilling was massively expensive.
Air source heat pumps now work down into pretty cold temperatures. With a high-efficiency air source our average heating/cooling bills are around $250 (down from ~$400 with older models). Even if ground-source got that down to $200, the payback period of the drilling would exceed our expected time in the house.
We still kind of wanted to do it, but the added problem was that no one in the area was really experienced with ground-source installs. So we would be dealing with the hassle of trying to get these HVAC guys to work on projects that they are not that interested in.
In the end we went with air-source, and it worked out very nicely.
Still, for heating, especially in really cold climates, a Heat Pump is going to have a hard time competing against other approaches, in efficiency, efficacy, and cost.
The latest gen of "ductless" or "mini split" units are awesome *AC* units (efficient, quiet), and I'd definitely recommend checking them out for cooling. If you're somewhere that it doesn't get too cold in the winter (lows in the mid-20s at the lowest), you might be able to tolerate using one for heating, but any colder and you're going to need another solution.
Cold and humid seem to be the worst combination from reviews I've seen for minisplits, because the second biggest problem is heat transfer, and transferring heat through ice is very inefficient. Every time the ice begins to insulate the coils, you have to run the system backward to heat the pipes above freezing and melt off the buildup. Not only does that lower the efficiency of the system but eventually it limits the duty cycle, because you can't be thawing and pumping at the same time. And so you are attacked from all sides by both physics and logistics.
Also, there are a lot of tax credits - 26% of the entire cost this year as a federal tax credit if you install this year (decreasing to 22% next year), and a number of state and local incentives bring the cost down significantly. And there are obviously financing options available.
If you combine it with a large solar array, I think the biggest thing it brings you is reducing uncertainty about future bills - you're locking in your expenses, a little like what buying a house does vs renting.
https://en.wikipedia.org/wiki/Hardiness_zone#/media/File:201...
Anywhere in yellow (8a) or warmer can use a heat pump, no problem -- the best heat pumps go down to about 0 F (-20 C) intake temperature. That's about half the country. With good construction it should work down to 7a (light green), and this transition zone includes DC/Philly/NYC. The darker green and blue regions need more advancements in the tech to rely on them.
But it's mostly the US that has this problem. By contrast, practically everyone in Latin America / Africa / Southern Asia should have no trouble switching to heat pumps (if they need heating at all, i.e. Zone <10):
https://upload.wikimedia.org/wikipedia/commons/a/a7/World_Ha...
Since many of these countries are industrializing during the efforts to mitigate global warming, hopefully they will get heating right sooner rather than later.
Mitsubishi makes a line that still has reasonable COP numbers down to -13F or so. It's a clever trick: the actual problem at these very low temperatures is that the refridgerant in the lines starts to get slushy as it approaches its own freezing point, but it still functions. So they actually steal a bit of the heat that would otherwise enter the heated space, and use it to slightly warm the refridgerant so that things keep ticking along.
https://m.youtube.com/watch?v=GhAKMAcmJFg
Interestingly the prediction he made, regarding gas prices, did come true.
Our main family room/kitchen is the largest room downstairs, and the only one we heat during the day in the winter. So rather than figure out the complexity and additional cost of an air-to-water, it seemed logical to dip our toes in with something simple.
It's been great. Our gas usage is less than half what it was the previous year. The room heats up faster in the mornings, so there's no need to have the heat on before we come downstairs. On cold days this winter, we were heating the whole downstairs for about 15kwh/day, meaning we're getting roughly a 3-4x COP real-world (closer to 4 i think, but have no way of precisely measuring). If I'm feeling chilly, I can sit directly under it in a nice warm breeze.
It cost £2,275 installed. The model was the Daikin-FTXP60M.
(Recognise that this does not necessarily undermine the argument in the video. But I do find it odd air-to-air source heat pumps are not considered more often in the UK)
Also interesting to compare this relatively modest investment with an electric car. Very roughly, the carbon savings we're seeing are comparable to the savings from replacing 10k miles per annum in an ICE with an electric (I think, rough back-of-the envelope calculation!).
Could be due to housing density and the reputation for noise, though I'm not sure how well-deserved that really is.
Mostly I just think it is a mismatch between the age of housing stock (and the pre-existing heating solutions) with incentives.
If I were building a new house I wouldn't bother with a gas supply and would use a ground-source heat pump combined with underfloor heating - but retrofitting that to my 150 year old house is never going to be cost effective versus a boiler.
For residential developments, the government should just mandate no new domestic gas supplies and be done with it.
Our air source heat pump is much quieter than old air conditioners. For efficiency, it has a giant, slow, variable speed fan. It's usually not running anywhere near full speed, and is still quiet when it does. Similarly, the blowers in the ducts are variable speed.
I do it yearly, but I suspect I'm breathing black spores 4 months in a year
But shouldn't these things be in a basement or utility room?
I can't hear mine though a double-glazed window.