I build controls for many heatpumps (https://flair.co/pages/mini-splits-and-window-units) and follow the space pretty closely. They are truly magical with respect to pumping heat from the cold outdoors into a warm indoor space.
That said, the efficiency gains on the energy consumption side are admirable. From a global warming standpoint however, heat pumps are actually still pretty bad because of the refrigerants.(https://www.drawdown.org/solutions/materials/refrigerant-man...) This is not an issue with more traditional electric heaters (resistive or otherwise).
The real calculus for those concerned with global warming (I understand this was not the topic of the writeup) is the net effect of these systems over their lifetime - aka, Energy Saved and its GHG effect via leveraging a heat pump vs the GHG effect from the release of the refrigerant. Perhaps the real win would be a refrigerant recovery business that is...air tight :)
I think when I did the numbers for our heat pump, a catastrophic leak that would release all its refrigerant would result in a GHG contribution equivalent to a year of emissions from our (previous) natural gas heating. Can't find the figures now so do check before quoting me on it ;)
Alternatively, Mitsubishi has been selling a first-generation product that uses CO2 as the refrigerant (the QUHZ model). It posts a COP of 3 for producing domestic hot water (that's pretty good) - I'm not sure why they don't post the COP for room heating, maybe it's not great. But I'm curious what the second-generation product will do!
There is a such thing as a solid state heat pump which operates without refrigerants or any moving parts. They are not as efficient as regular heat pumps, though, at least currently. But maybe that could change.
Modern heat pumps are truly a marvel, especially when you get one designed for heating and not just an AC-unit running in reverse. They're very common in Sweden and can easily warm an entire house even at -20 C.
Whenever this topic appears on HN I want to get on my soapbox and yell "INSULATION PEOPLE, INSULATION!". Most houses I've seen outside of the Nordics have shit-all insulation and that's depsite it working both ways - house stays cooler in the summer. It's such a small cost to add during construction and it pays off in a year or two, tops.
Modern, newly built houses in Sweden, way above the arctic circle, require less than 5000 kWh per year to heat and generate hotwater.
> It's such a small cost to add during construction and it pays off in a year or two, tops.
Classic market failure: operational costs don't factor into home buying decisions prominently, so whatever small added construction cost is borne by the homebuilders (the cost of added insulation doesn't quite result in an equal increase of selling price).
Short of instituting a carbon tax that would make operational costs of heating suddenly more prominent and priced accordingly, this is a great case for efficiency standards in homebuilding. Suppose your home came with an "energy star" HVAC rating...
Yes, insulation, but that's not without its problems either. If you're adding insulation to an old house you have to consider that the ventilation system in that house is probably gravity-based. What that means is hot air moves upward, through an unheated attic in the type of house I'm thinking of, and replacement air is pulled in through the breathable structures of the walls. When you insulate such a house heavily, that air intake is compromised and you lose ventilation. So for an insulated house you may need to add mechanical ventilation, which underpressurizes the house. You now need to add air vents, but if you don't have enough of them, replacement air may get drawn e.g. from the understructure of the house, pulling soil microbes into the air with it. Also, if you insulate in such a way that the breathability is compromised, you risk moisture problems, which lead to mold. In particular, adding modern fibreglass insulation to an old house is very problematic, because that type of insulation should not be allowed to draw moisture as it will not dry out and will grow moldy, and wood structures in contact with it may rot.
Basically, moisture control and insulation is a tough problem. In modern houses the solution is to have an airtight layer of plastic sheeting between the insulation and drywall, but those houses should also have been designed from the ground up to have an active, mechanical ventilation system.
Based on experiences here in Finland, a lot of such buildings built in the 60's and 70's have developed severe problems, and frankly even new projects seem to have issues all the time. The more you insulate, the more you have to take care that moisture does not gather in the insulation because you no longer have airflow that would dry it out.
I've gone through the exercise of retrofitting insulation. Unfortunately there are a few things that are extremely hard to get past. 2x4 walls can only be insulated to R-13 or so unless you're replacing the siding. Subslab insulation can pretty much only be done when it's poured. Joist insulation & air sealing can be very hard to get to.
I can only hope 2x6 framing becomes more common, the subslab insulation has started to become code.
It seems residential natural gas prices in Sweden are almost 4 times what they are in the US! Show what a carbon tax can do in changing economic decision making.
Air sealing is also critical. The insulation can be defeated if unconditioned air can leak into the house and conditioned air can leak out. It's a difficult thing to get right because it requires attention to detail and if done poorly it can result in moisture problems.
UK is finally getting there, but we have a very long way to go. Our housing is mostly bloody awful for insulation, draught proofing, and sensible forms of heating. The very worst is anything 60s-90s, particularly if there's a flat roof.
We've only been hearing about how well Sweden and other Nordics do insulation, community heating, heat pumps etc for about 40 or 50 years. Various combined heat and power, insulation, passive houses etc would turn up on things like Tomorrow's World (60s-90s technology TV series) fairly often, like it was some sort of breakthrough new discovery. Well it was, to the UK, I guess.
Insulation is probably the most important mechanical energy saving feature of a house. Unfortunately it is behind the drywall and as they say "out of sight and out of mind". We built a very large cottage (3000 sq/ft) in Northern Ontario, Canada. The entire house had a continuous envelope of a minimum of 4-5 inches of Closed Cell Foam (2 lb) ( https://www.demilec.com/ ) . Installed a Geo-Thermal Unit with in floor heating through out the basement and forced air everywhere else. We also have a high efficiency fireplace stove. It can be minus 40 C outside and you only need a couple of logs in the fireplace to keep the entire cottage very warm.
You can change out your furnace/AC/Heat Pump anytime, but try tearing off all the drywall in your entire house to replace the fiberglass insulation that doesn't work or was installed incorrectly. Spray Foam Insulation pays for itself and to think it's only around $3.00 a sq/ft at 3 " thick installed. People have no problem paying more for carpeting or tile floors, strange....
Many Swedish suburbs are supplied with communal hot water for heating (fjärrvärme) produced by burning non-recyclable rubbish or maybe a local factory. The last stage of houses built near us was so thermally efficient that the supplier refused to extend the heating network, as there was not enough consumption to generate a profit. When I lived in New Zealand I could see my breath indoors in the winter. Insulation? I'm a convert.
I have a 2 story house with a heat pump for the upstairs...and I hate it. It causes so many problems that we just keep the heat very low up there so that the heat drift from the 1st floor furnace does most of the work.
When it runs, you can never set it higher than 2 degrees F above the current temperature and if you do that when it's even close to freezing outside the unit will build up a think layer of ice around the casing...which just makes it spin constantly until we turn it off to go manually de-ice it. It's the most hated piece of equipment in my entire home.
Do you have a reference for one of these more effective modern heat pumps? I've been sincerely planning to install geothermal when this thing dies.
> I want to get on my soapbox and yell "INSULATION PEOPLE, INSULATION!".
I'm joining you in that. I'm in Dubai at the moment thanks to airspace closure over Pakistan.
I noticed that richer Middle Eastern countries are the few places outside of the ex-USSR where foamed concrete picked up popularity as an insulation material. Seems to be a very popular choice for detached housing here.
I also noticed that despite the fabulous wealth, glass curtainwalls are not so widespread here. Even the most "skyscrapery" skyscrapers here have some solid walls and/or external shading (even Burj Khalifa on some levels.)
Are houses in the Nordics framed with wood? I was having a discussion with someone the other day about houses in the U.K. They felt stone houses were far superior to the wood ones in the US. I tried to convince him about insulation being much better in wood frames homes in mild and cold climates to no avail.
My exposure to the Nordics is limited but in the pictures I’ve seen there were lots of wood single family houses.
One thing to add to insulation, make sure your cooking appliances have decent internal insulation too; otherwise you may find your gas oven overwhelming whatever natural radiative qualities your home has, even with all the windows open. Not a fun thing to learn when your AC gets knackered in the florida heat.
Is -20 a practical limit for them working in your experience or is this just a convenient low number for the sake of an example. I assume that is Sweden the temp can drop below that at times in the middle of winter. Are housing using them using a backup heat source as well?
On the west coast of Canada we'd probably never hit -20, but lots of other parts of the country do regularly.
Also worth mentioning is that Sweden pushes a lot of retrofitting of older houses, not just new ones. In the 90's, triple-pane windows became a legally mandated standard, so every old apartment building that only had double-pane windows had to add a third pane somehow, or change out all the windows or whatever.
A lot of older buildings are also adding extra insulation, one complex I used to live in that was built in the 1940's did that after I moved out. They stripped off all the outer layers to get to the brick, added foam insulation blocks, and redid the plaster finish.
When I lived there, the complex did the mandatory energy certification and got a shit score, so that's why they had to do it.
The Google X spinoff Dandelion Energy is now testing in my area, and I have been experiencing frequency illusion with geothermal heating since I saw an ad for it.
I do wonder how X's technology compares to existing household products, though.
My dad is such a pain in the ass about this - he'll turn the heat down to 15 degrees in any room that's not currently occupied, and whenever they leave the house. So the place is always uncomfortably cold, there are hot spots/cold spots and drafts. Meanwhile there's minimal insulation in the attic and zero insulation under the floors, and a huge basement that's always cozy and warm all winter, despite the fact that there's no heating in there.
Then he complains about the heating bill and blames me for it (because I cranked the heat when I came over for dinner one night). What a mystery.
I experienced a modern heat pump in action for the first time about a year ago, when I was visiting family in the very cold US state of Maine -- creaky old [and ill-insulated] house in the woods heated up in a jiffy! Hats off to the engineers who work on this stuff.
p.s. even though the refrigerants are bad, still a mile better than the old oil heaters everybody used when I was a kid
What about at the other end of the spectrum? We wanted temperature control in our garage so we had a heat pump installed. The company told us that heat pumps stop working for cooling around 38 C which kind of sucks because that's when we want it the most.
To be fair, here in California, all newer homes have insulation preinstalled. I think there may still be a tax credit to help have your home insulated if it doesn't have any insulation.
It's worth noting that the temperatures at which heat pumps function well is more of a design choice than a fundamental limitation. You can make a heat pump which functions down to -20C with HFC refrigerants, maybe lower with some other types. However, you may choose to optimize 'mild weather' performance by forgoing low temperature performance. Modern heat pumps work pretty darn well across a range of temperatures.
What we really need are heat pumps which do not use HFC refrigerants - they are a pretty significant cause of global warming, and there are other options (CO2 being one of the best, in my opinion). https://www.drawdown.org/solutions/materials/refrigerant-man...
Heat pump water heaters have efficiency of 3x+ vs .9 or so for gas or electric resistance. If you have have an electric resistance water heater get a heat pump model. It costs more upfront but will pay for itself in not too many years, especially considering many places have incentives. In the US natural gas is so cheap the economics are not nearly as good, it takes a long time to pay back the difference but does eventually. With even a modest carbon price obviously this would be different.
If you are going to replace your furnace or AC get a quote for replacing with a heat pump instead, either central or multiple mini-split heads. Heat pumps have gotten a lot better in recent years, particularly being able to work in cold weather down to 0F or below, expanding northward the places they are practical.
Electric resistance heat is 1.0 or 100% efficient, all electricity put into the heating element is converted to heat. Not sure if your trying to include power plant conversion and transmission losses, but that gets very complicated.
Gas units range in efficiency based on how much heat they recover from the exhaust, 80% is typical, 90+ for a condensing heater with two stage heat recovery. The problem with condensing is the exhaust gases fall below condensation point for the water vapor created during combustion requiring a condensate drain complicating the install location and cost significantly.
Heat pumps are over unity they use some energy to move more energy from the environment into the water, they are basically solar assisted resistance heaters.
The energy cost difference is not as clear when comparing a heat pump tank storage unit to a gas on demand tankless they are both typically more cost effective than tank storage electric or gas.
I have a 80% efficient tankless natural gas, it is wonderful having endless hot water at all faucets concurrently with a family of 4 plus occasional guests. I wanted to go condensing 90+ efficient but it was to complex based on its install location.
Speaking specifically of heat pump water heaters - I will absolutely cede that they are more efficient, but holy _crap_ they take forever to recover.
My previous water heater was a 70 gallon conventional electric. It didn't have quite enough hot water to get everyone through showering when we had extended family over, but it recovered reasonably quickly so that we only had ~ 30 minute gaps or so in waiting between the person who felt it get cold first and the next in line. Pretty reasonable.
Ours was about 20 years old and we also wanted a bunch of other plumbing work done, so we decided we may as well bite the bullet and get a new one. We replaced ours with an 80 gallon hybrid (electric + heatpump). We figured the extra 10 gallons would probably actually completely negate the need to wait between showers for those last people, so we were super stoked.
The reality is it exacerbated matters drastically. The refresh rate on our old water heater apparently was almost good enough to keep up with sustained usage between 7 people. The current one runs out of hot water out of 2 and takes well over an hour to even have enough hot water for a single next shower.
I tend to take pretty long showers in the morning - like 20 minutes or so. I use a CPAP and clean my mask, I brush my teeth, I brush my invisaligns (which is why I do my teeth in the shower - it's impossible to scrub invisalign braces and not fling infinite toothpaste flotsam everywhere), and I wash myself (which honestly is the fastest part - I keep my hair next to non existent and just do a body wash from head to toe, rinse, and leave. The point is that the 20 minutes I spend in the shower, with a low flow water reducing showerhead, still means my wife gets to get a cold shower an entire hour later.
However, from what I was told, there are new regulations regarding electric hot water heaters; namely, you can't get over 60 gallon tanks with a conventional hot water heater. Apparently people are getting around this by buying light industrial ones, which don't have this limitation. I wanted to try to cut down on energy usage AND I was keen on the idea of having a heat pump in my garage, transferring the heat in said garage into the water, thus leaving the garage cooler. It's like a really inefficient air conditioner for my garage, but given how hot that gets in the summer and how little I spend time in my woodworking shop, I wanted to leap at the chance to maybe make it a better environment.
All of this is a long winded way of saying it may win on efficiency, and it does have a number of compelling secondary features about it, but it also still suffers from poor refractory performance. If you have one as well - do you notice issues like this? Perhaps the one I got is faulty or just ... not good.
I can tell you that my heat pump set up at my condo is absolute trash here in Northern Ohio. Running 24/7 it is unable to get my condo above 62 deg F. It blows cold-ish air under an outside temperature of 40 deg F. Windows are new, doors are weather stripped. I'm having it run it in supplemental mode just to get it above 65 deg F.
Big issue in the Netherlands (and probably more countries) will be noise pollution though. Houses here are built really close to each other and the combined noise could be an issue. Neighbours are already complaining about the noise from my parents heat pump.
The most recent season of This Old House, Jamestown Net-Zero House[0], is worth a watch for folks interested in learning more about home efficiency techniques in general.
I had a "geothermal" heat pump put in to my house via Google's Dandelion and it works great so far. It's been -30F at my house but the ground sourcing renders that moot. As far as I can tell their innovation was going vertical so they didn't need to dredge up a huge loop of land. The pump has two channels that go down 300ft each and the fluid runs down and back up each bore hole.
It provides heat (working great so far), hot water (but I already had an electric inline heater, so I can't speak to the slow-refill issues), and A/C in the summer. I'm curious to see how well the AC performs!
Maybe I'm missing something, but no matter how efficient a heat pump is, doesn't it have a limit on how much heat it can pump as ∆T increases?
Even here in western NY we occasionally have to deal with -10 F (-23 C) weather for a week and so that's a pretty big temperature delta if you want a comfortable 68 F (20 C).
Combine that with the fact that gas is still quite a bit cheaper per unit of energy than electricity (in my area) and a heat pump just doesn't make any sense.
The ability to have a single unit heat and cool is definitely nice, but without a geothermal-like ambient temperature to work with, I just don't see this working out, even with all the insulation in the world.
Question to other engineers here. We were designing a "smart wine chiller" recently. Ran into a problem - small size sealed compressors are very, very, hard to come by, and if you want one that is also quiet, prepare your arm and a leg.
We ended up having the compressor custom made by local fridge factory. Engineers there told us that designing such a small piston compressor and hoping it to be reliable and efficient is a futile effort, but they still did their best.
Is between piston driven compressors, and peltier coolers, is there just anything on the market? More quiet and robust than small piston compressors, and more efficient than peltier?
The most commonly used heat pumps utilize the external air as a source. Which is quite silly on a sunny but chilly day.
Even 2m^2 black & isolated panel exposed to the sun will be tens of degrees warmer. Just putting the heat exchanger in some micro glass house with a valve would increase the efficiency.
We have a heat pump and I love it, but for the longest time it was beyond me how the thing works. When it finally clicked, it blew my mind. The idea that there’s heat to be found, even on a cold day, is amazing. It’s actually what made me want to understand thermodynamics more deeply.
This was a really lucid and engaging piece on the mathematics of these systems. I wish more math teachings would be done in long form like this instead of the cargo culted textbooks that are put out by major publishers.
Heat pumps based on air do not work economically below 40F. Neighbor has one and his electric bill is out of control in the winter. Drop below freezing and the system will pump heat out of the house to de-ice the external unit, and electric resistance heat will kick in.
We have dual fuel, so we burn oil below 40F. Works great.
If you can afford it, putting in a heat pump that works off of ground will eventually pay for itself.
[+] [-] danimal88|7 years ago|reply
That said, the efficiency gains on the energy consumption side are admirable. From a global warming standpoint however, heat pumps are actually still pretty bad because of the refrigerants.(https://www.drawdown.org/solutions/materials/refrigerant-man...) This is not an issue with more traditional electric heaters (resistive or otherwise).
The real calculus for those concerned with global warming (I understand this was not the topic of the writeup) is the net effect of these systems over their lifetime - aka, Energy Saved and its GHG effect via leveraging a heat pump vs the GHG effect from the release of the refrigerant. Perhaps the real win would be a refrigerant recovery business that is...air tight :)
[+] [-] yungchin|7 years ago|reply
Alternatively, Mitsubishi has been selling a first-generation product that uses CO2 as the refrigerant (the QUHZ model). It posts a COP of 3 for producing domestic hot water (that's pretty good) - I'm not sure why they don't post the COP for room heating, maybe it's not great. But I'm curious what the second-generation product will do!
[+] [-] fallingfrog|7 years ago|reply
https://www.researchgate.net/publication/270646164_Efficienc...
https://www.energy.gov/eere/buildings/downloads/high-efficie...
https://arpa-e.energy.gov/?q=slick-sheet-project/high-effici...
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] ars|7 years ago|reply
[+] [-] fastbeef|7 years ago|reply
Whenever this topic appears on HN I want to get on my soapbox and yell "INSULATION PEOPLE, INSULATION!". Most houses I've seen outside of the Nordics have shit-all insulation and that's depsite it working both ways - house stays cooler in the summer. It's such a small cost to add during construction and it pays off in a year or two, tops.
Modern, newly built houses in Sweden, way above the arctic circle, require less than 5000 kWh per year to heat and generate hotwater.
[+] [-] floatrock|7 years ago|reply
Classic market failure: operational costs don't factor into home buying decisions prominently, so whatever small added construction cost is borne by the homebuilders (the cost of added insulation doesn't quite result in an equal increase of selling price).
Short of instituting a carbon tax that would make operational costs of heating suddenly more prominent and priced accordingly, this is a great case for efficiency standards in homebuilding. Suppose your home came with an "energy star" HVAC rating...
[+] [-] rebuilder|7 years ago|reply
Basically, moisture control and insulation is a tough problem. In modern houses the solution is to have an airtight layer of plastic sheeting between the insulation and drywall, but those houses should also have been designed from the ground up to have an active, mechanical ventilation system.
Based on experiences here in Finland, a lot of such buildings built in the 60's and 70's have developed severe problems, and frankly even new projects seem to have issues all the time. The more you insulate, the more you have to take care that moisture does not gather in the insulation because you no longer have airflow that would dry it out.
[+] [-] ip26|7 years ago|reply
I can only hope 2x6 framing becomes more common, the subslab insulation has started to become code.
[+] [-] thinkcontext|7 years ago|reply
https://www.statista.com/statistics/702735/household-natural...
[+] [-] leguminous|7 years ago|reply
[+] [-] NeedMoreTea|7 years ago|reply
We've only been hearing about how well Sweden and other Nordics do insulation, community heating, heat pumps etc for about 40 or 50 years. Various combined heat and power, insulation, passive houses etc would turn up on things like Tomorrow's World (60s-90s technology TV series) fairly often, like it was some sort of breakthrough new discovery. Well it was, to the UK, I guess.
[+] [-] hourislate|7 years ago|reply
You can change out your furnace/AC/Heat Pump anytime, but try tearing off all the drywall in your entire house to replace the fiberglass insulation that doesn't work or was installed incorrectly. Spray Foam Insulation pays for itself and to think it's only around $3.00 a sq/ft at 3 " thick installed. People have no problem paying more for carpeting or tile floors, strange....
[+] [-] nray|7 years ago|reply
[+] [-] brightball|7 years ago|reply
When it runs, you can never set it higher than 2 degrees F above the current temperature and if you do that when it's even close to freezing outside the unit will build up a think layer of ice around the casing...which just makes it spin constantly until we turn it off to go manually de-ice it. It's the most hated piece of equipment in my entire home.
Do you have a reference for one of these more effective modern heat pumps? I've been sincerely planning to install geothermal when this thing dies.
[+] [-] baybal2|7 years ago|reply
I'm joining you in that. I'm in Dubai at the moment thanks to airspace closure over Pakistan.
I noticed that richer Middle Eastern countries are the few places outside of the ex-USSR where foamed concrete picked up popularity as an insulation material. Seems to be a very popular choice for detached housing here.
I also noticed that despite the fabulous wealth, glass curtainwalls are not so widespread here. Even the most "skyscrapery" skyscrapers here have some solid walls and/or external shading (even Burj Khalifa on some levels.)
[+] [-] wil421|7 years ago|reply
My exposure to the Nordics is limited but in the pictures I’ve seen there were lots of wood single family houses.
[+] [-] tomatotomato37|7 years ago|reply
[+] [-] mmartinson|7 years ago|reply
On the west coast of Canada we'd probably never hit -20, but lots of other parts of the country do regularly.
[+] [-] henrikschroder|7 years ago|reply
Also worth mentioning is that Sweden pushes a lot of retrofitting of older houses, not just new ones. In the 90's, triple-pane windows became a legally mandated standard, so every old apartment building that only had double-pane windows had to add a third pane somehow, or change out all the windows or whatever.
A lot of older buildings are also adding extra insulation, one complex I used to live in that was built in the 1940's did that after I moved out. They stripped off all the outer layers to get to the brick, added foam insulation blocks, and redid the plaster finish.
When I lived there, the complex did the mandatory energy certification and got a shit score, so that's why they had to do it.
[+] [-] mixmastamyk|7 years ago|reply
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] schnevets|7 years ago|reply
I do wonder how X's technology compares to existing household products, though.
[+] [-] Kluny|7 years ago|reply
Then he complains about the heating bill and blames me for it (because I cranked the heat when I came over for dinner one night). What a mystery.
[+] [-] MisterOctober|7 years ago|reply
p.s. even though the refrigerants are bad, still a mile better than the old oil heaters everybody used when I was a kid
[+] [-] criddell|7 years ago|reply
[+] [-] vondur|7 years ago|reply
[+] [-] bzbarsky|7 years ago|reply
For what size house, if I might ask?
[+] [-] jjtheblunt|7 years ago|reply
[+] [-] unknown|7 years ago|reply
[deleted]
[+] [-] torpfactory|7 years ago|reply
What we really need are heat pumps which do not use HFC refrigerants - they are a pretty significant cause of global warming, and there are other options (CO2 being one of the best, in my opinion). https://www.drawdown.org/solutions/materials/refrigerant-man...
[+] [-] thinkcontext|7 years ago|reply
If you are going to replace your furnace or AC get a quote for replacing with a heat pump instead, either central or multiple mini-split heads. Heat pumps have gotten a lot better in recent years, particularly being able to work in cold weather down to 0F or below, expanding northward the places they are practical.
[+] [-] SigmundA|7 years ago|reply
Gas units range in efficiency based on how much heat they recover from the exhaust, 80% is typical, 90+ for a condensing heater with two stage heat recovery. The problem with condensing is the exhaust gases fall below condensation point for the water vapor created during combustion requiring a condensate drain complicating the install location and cost significantly.
Heat pumps are over unity they use some energy to move more energy from the environment into the water, they are basically solar assisted resistance heaters.
The energy cost difference is not as clear when comparing a heat pump tank storage unit to a gas on demand tankless they are both typically more cost effective than tank storage electric or gas.
I have a 80% efficient tankless natural gas, it is wonderful having endless hot water at all faucets concurrently with a family of 4 plus occasional guests. I wanted to go condensing 90+ efficient but it was to complex based on its install location.
[+] [-] isbjorn16|7 years ago|reply
My previous water heater was a 70 gallon conventional electric. It didn't have quite enough hot water to get everyone through showering when we had extended family over, but it recovered reasonably quickly so that we only had ~ 30 minute gaps or so in waiting between the person who felt it get cold first and the next in line. Pretty reasonable.
Ours was about 20 years old and we also wanted a bunch of other plumbing work done, so we decided we may as well bite the bullet and get a new one. We replaced ours with an 80 gallon hybrid (electric + heatpump). We figured the extra 10 gallons would probably actually completely negate the need to wait between showers for those last people, so we were super stoked.
The reality is it exacerbated matters drastically. The refresh rate on our old water heater apparently was almost good enough to keep up with sustained usage between 7 people. The current one runs out of hot water out of 2 and takes well over an hour to even have enough hot water for a single next shower.
I tend to take pretty long showers in the morning - like 20 minutes or so. I use a CPAP and clean my mask, I brush my teeth, I brush my invisaligns (which is why I do my teeth in the shower - it's impossible to scrub invisalign braces and not fling infinite toothpaste flotsam everywhere), and I wash myself (which honestly is the fastest part - I keep my hair next to non existent and just do a body wash from head to toe, rinse, and leave. The point is that the 20 minutes I spend in the shower, with a low flow water reducing showerhead, still means my wife gets to get a cold shower an entire hour later.
However, from what I was told, there are new regulations regarding electric hot water heaters; namely, you can't get over 60 gallon tanks with a conventional hot water heater. Apparently people are getting around this by buying light industrial ones, which don't have this limitation. I wanted to try to cut down on energy usage AND I was keen on the idea of having a heat pump in my garage, transferring the heat in said garage into the water, thus leaving the garage cooler. It's like a really inefficient air conditioner for my garage, but given how hot that gets in the summer and how little I spend time in my woodworking shop, I wanted to leap at the chance to maybe make it a better environment.
All of this is a long winded way of saying it may win on efficiency, and it does have a number of compelling secondary features about it, but it also still suffers from poor refractory performance. If you have one as well - do you notice issues like this? Perhaps the one I got is faulty or just ... not good.
[+] [-] heatpumper|7 years ago|reply
[+] [-] donkeyd|7 years ago|reply
[+] [-] cdubzzz|7 years ago|reply
[0] https://www.thisoldhouse.com/watch/jamestown-net-zero-house
[+] [-] lxmorj|7 years ago|reply
It provides heat (working great so far), hot water (but I already had an electric inline heater, so I can't speak to the slow-refill issues), and A/C in the summer. I'm curious to see how well the AC performs!
[+] [-] jstapels|7 years ago|reply
Even here in western NY we occasionally have to deal with -10 F (-23 C) weather for a week and so that's a pretty big temperature delta if you want a comfortable 68 F (20 C).
Combine that with the fact that gas is still quite a bit cheaper per unit of energy than electricity (in my area) and a heat pump just doesn't make any sense.
The ability to have a single unit heat and cool is definitely nice, but without a geothermal-like ambient temperature to work with, I just don't see this working out, even with all the insulation in the world.
[+] [-] baybal2|7 years ago|reply
We ended up having the compressor custom made by local fridge factory. Engineers there told us that designing such a small piston compressor and hoping it to be reliable and efficient is a futile effort, but they still did their best.
Is between piston driven compressors, and peltier coolers, is there just anything on the market? More quiet and robust than small piston compressors, and more efficient than peltier?
[+] [-] DoofusOfDeath|7 years ago|reply
I live in a temperate climate. I've sometimes wondered if it would be worthwhile to adjust house construction so that:
- In the summer, the kitchen refrigerator's heating coils touch outdoors air instead of indoors air.
- In the winter, the refrigerator's cooling is provided, at least partially, by the outside air.
- In the summer (only), the kitchen oven vents into the outdoors rather than into the kitchen.
- In the winter (only), a heat exchanger recovers some of the heat from our electric clothes dryer.
[+] [-] unknown|7 years ago|reply
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[+] [-] elmolino89|7 years ago|reply
[+] [-] gdubs|7 years ago|reply
[+] [-] Pulcinella|7 years ago|reply
https://en.m.wikipedia.org/wiki/Joule–Thomson_effect
[+] [-] kev009|7 years ago|reply
[+] [-] agumonkey|7 years ago|reply
Right now it's mostly wasted heat, or IIUC even worse, in closed spaces it forces more energy consumption from the fridge.
[+] [-] unknown|7 years ago|reply
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[+] [-] wazoox|7 years ago|reply
[+] [-] tomohawk|7 years ago|reply
We have dual fuel, so we burn oil below 40F. Works great.
If you can afford it, putting in a heat pump that works off of ground will eventually pay for itself.