200-year old heat pump technology is back
yaleclimateconnections.org
yaleclimateconnections.org
https://youtu.be/7J52mDjZzto https://youtu.be/MFEHFsO-XSI https://youtu.be/7zrx-b2sLUs https://youtu.be/43XKfuptnik
It's absolutely something I wouldn't take on myself though. Changing a light switch or rewiring a plug, sure - but I'd be guaranteed to make a huge, expensive, inefficient mess with a project like that.
It is a bit expensive to put in, so I wouldn't do it unless you plan to live there long enough to recoup the costs. If I were to sell my house nobody would give me a dime extra for it.
It was eye opening. I got a taste of exactly why builders build crap homes. Building code is the minimum and they build to it for a reason.
We are now friends with the people who bought it and several times they have thanked us for building it well. They didn't know what they were getting, but it is nice to see they appreciate it now - especially when the power is out and neighbors are crying about their cold houses and these lucky people are staying warm.
My third and final build I built for me. I never plan to sell. Even when my kids are gone and I only need half the house it would be very hard to find something to downsize to that would cost me less per month than I pay now. Ground source is that good.
Do you think this is really an information asymmetry problem? What if there was a standardized way to compare the cost of maintenance per M2?
Anecdotally it doesnt seem to have a huge impact on the asking price.
My house is from 1935 and the statistics tell me that it is practically impossible for me to get the house above C. I think that it is theoretically possible but the required investment will be so big that it makes more economic sense to tear the house down and build it with modern materials and techniques.
https://sparenergi.dk/forbruger/vaerktoejer/find-statistik-p...
[0] https://energysavingtrust.org.uk/advice/guide-to-energy-perf...
Of course, most people haven't cared that much about it. But it's changing with higher energy prices. I had a friend regretting buying something with grade F, for same square meters he pays like 10x the amount for heating than I do in my C apartment. (scale from A..G)
I put in two Mitsubishi H2i systems last year and have had some pretty insane energy bills due to sizing them too large (A general overview of why here: https://carbonswitch.com/heat-pump-sizing-guide/)
Once I get my solar in place I won't feel too bad about this, but for now has been a bummer as was expecting a real efficient beast.
I replaced my old (95kBTU/hour output) forced-hot-water furnace and separate hot water heater with a condensing furnace about eight years ago. I got a heat loss calculation done, which concluded I only needed 59kBTU/hr of heat. It was a struggle to get a small-enough furnace installed; one contractor said he couldn't in good conscience sell me anything smaller than 120kBTU/hr.
My final system was 89kBTU/hr. A couple of weeks ago, in record -13°F/-25°C cold and high winds, it was burbling along at 60% power. Could have been even smaller.
And it provided ac in the summer which we didn't have previously.
There are some downsides, it was expensive to put in and the outdoor unit is loud. While it does save us money, it probably wouldn't make sense as something that will pay for itself in heating costs with current propane prices and natural gas is much cheaper if you can get it. But definitely makes sense for new construction especially when paired with a wood or propane stove for back up heat in power outages/ambiance/quick heating.
This will turn the noise into a slight murmur.
Americans on this site always mention grid failures as a concern about electric heating/cars/whatever.
While I won’t claim that power failures never happen where I live, because they do…but they’re very very rare and short enough not to care. The only exceptions are major natural disasters like hurricanes.
Americans, why do you have such a terrible electricity distribution grid?
Which is the same as with us Americans.
My last apartment had a handful of power outages and all except one was due to weather. The exception was a transformer that exploded — which seems common as I’ve seen at least three just randomly go boom.
When you get major weather events, where they are pulling in personnel from all over the nation, is when people get concerned about electric heating because it might take a while to get to them.
Lots of above ground power lines in heavily forested suburban sprawl means lots of branches in lines every wind storm and they (private) electric co has to visually check all of them before they can turn power back on.
Despite being much more rural the power coop that serves me now seems to never have an outage that lasts more then a few hours. Probally mostly because they have much less pine to check.
Very very spread out population.
And huge spikes and troughs of infrastructure investment over decades.
Anyway, where I live in Boise most utility outages are due to physical damage - whether that be animals, auto accidents, extreme weather (not “it got cold”, but wind gusts toppled a tree that brought down a utility pole), and fiber seeking backhoes. Even had the gas get shut off at my old house because an auto accident hit some equipment a street down causing a gas leak.
Many rural houses have tanks on site because there are no public gas lines to connect to. My house has a 1000 gallon tank and is not vulnerable to the above, for example.
eg: https://en.wikipedia.org/wiki/Natural_gas_storage#Pipeline_c...
There may be more than a day of capacity just in the pipe network.
I'm sure there are exceptions, but I've never heard of one.
I will compare a nominal 3Ton = 36,000 BTU/h (10.55kW) furnace+AC running at about 1200CFM with gas fuel input at 45,000 BTU/h to similar heat pump system outputs and electric resistance heat.
The central furnace fan is probably about 1/2 horsepower rating (372W) and has some design tolerance built in where the brake horsepower is less than this. The heating output at 80% efficiency is 36,000 BTU/h (10.55kW). This output is constant regardless of outside temperature. This could be run with a small inverter generator or possibly a robust battery system in the 20kWh range with appropriate solar.
Note that the heating input for this size of furnace can go up to ~155,000 BTU/h (45.4kW) with only the same amount of fan power needed in the form of electricity.
Looking through Mitsubishi literature, a 3ton hyper heat pump (SUZ-KA36NAHZ) at 17f can deliver 25400 BTU/h (7439 W) of heat output with an input of 2490 W. You will need strip heat to supplement this output to make up the difference (10.55kW - 7.439kW = 3.1kW of electric heat) So total power input is 3.1kW + 2.49kW = 5.6kW input for 10.55kW output. This might be short a few hundred watts as you still have to run the fan. This could be done with a larger portable generator.
http://mylinkdrive.com/USA/M_Series/R410A_Systems-1/Outdoor_...
Electric resistance heat would need the full 10,550 W to equal the output and now you need a relatively large fixed natural gas generator and transfer switch.
My personal opinion is that a heat pump system for normal operation with a natural gas or propane furnace as backup emergency heating is a good option to cover emergency situations as much as possible without adding an additional separate system like a wood burning heater or similar device.
My well pump is electric and I haven't been out of power long enough to be concerned about getting water.
It’s very common for branches to break and knock out power lines in the summer during windy storms.
This usually means no power for 1-3 day stretches and only happens 1-3 times per year. So worst case it’s no power for 9 days total every year.
The problem is it usually hits in the hottest days of the year so people really complain — myself included.
WFH also makes matters more complicated.
My local utility pays 50 EUR starting 12 hours after the start of an outage, and 4 EUR/hr after that. So a 2 day outage would pay out 200 EUR, and it all happens automatically.
There's no exceptions to this (only if you are at fault...), and this gets subtracted from their regulated revenues such that it hits the bottom line.
Naturally, most low voltage distribution lines are buried under ground
Our neighbourhood had an outage last winter during the -40 cold snap, and we were definitely at risk of water pipes freezing (gas fireplace was on, but without circulation it didn’t matter). The potential structural damage repair costs from outages up here would be insane, which makes me wonder if that’s part of why our grid seems so reliable (compared to other countries, anecdotally).
Recently, I stayed for three months on a mountain in Virginia. We lost power at least 6 times, usually for multiple hours. Once it was out half the day. There's a good reason the proprietor there keeps a backup generator on automatic failover.
[0] https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=W...
In the SF Bay Area, our last PG&E bill split across Jan/Feb was effectively $3.05/therm. The actual pricing in our bill reflects tiered pricing, with different tier thresholds in each month. The first tier covers up to 2 therms/day in Jan and 1.48 therms/day in Feb. The price tiers were $2.68..$3.06/therm in Jan and $2.75..$3.14/therm in Feb.
The bill also described $1.37/therm and $1.44/therm procurement prices for Jan and Feb, respectively.
It used to be much cheaper so a lot of old houses that aren't near a natural gas line were built with propane heat. You might save $200-1000 a year by switching to a heatpump but that means 10+ years to offset a ~$10000 install cost for a large unit professionally installed with a new 220 circuit run for it etc so most people just keep paying for propane or maybe use small electric space heaters.
And if you are somewhere you need to worry about pipes freezing in power outage a while you are away or temps bellow the heatpumps minimum -15f range a propane stove is a nice option. Relatively cheap to install and they can be setup to run on a thermostat with no grid power.
If i was building a new house i'd go heatpump + a propane stove for back up heat and a dual fuel induction/propane range.
No, wrapping a compressor in a blanket doesn't make it overheat. Compressors are cooled by the refrigerant running through them, not through heat lost through the casing.
Is that basically 'just' a different refrigerant (and whatever necessary engineering to cope with it)?
It is more than a heat pump, it is a new Stirling engine architecture, so it can run in reverse (heat to electricity) with an exceptional efficiency
You can not just send people checks and expect things can go well.
A typical Texas house has one unit that is both AC and furnace.
Most houses built in the last 50 years have central AC. Given that you'll have ducts, the simplest and easiest way to heat the house is to use them. In other words, it's forced air heating. It's really not a great form of heating, but it's adequate for relatively short, mild winters.
So if you replace your one AC/furnace unit with a heat pump unit, you probably won't have a gas furnace anymore to do the comparison. (Apparently, there is such a thing as a "dual fuel heat pump", though, which can heat with gas or heat pump. I'm not sure how much those cost.)
Another factor is that AC is the bigger concern for energy usage because AC is used much more of the year. So when replacing your system, whatever money you can spend on an upgrade, you're probably better off putting it toward improving AC efficiency rather than heat efficiency. Or toward something that will help with both, like insulation.
Given that an AC is just heat pump, but with the hot bit outside, and the only thing needed to swap the hot and cold bits is a reversing valve. A high efficiency heat pump is also a high efficiency AC (that’s a very tautological statement).
So investing in improved heat pump for heating, naturally means investing in an improved heat pump for cooling.
But in Texas, a heat pump wound probably be great. But yeah, natural gas is cheap.
The only people willing to install heatpumps are from an hour away and who spend their time building luxury homes. It's crazy to me that the rest of these guys aren't out there working with those Federal IRA funds and installing heat pumps left and right. We're climate zone 4 with a design temp of 6ºF, just about every modern HP will spend 99.9% of its time working at full BTU here.
With the way supply chains are right now, getting a less common unit means if you have a problem, and you will because half the components are imported now, you're going to be sweating it out while you wait 3-6 months for a part, and that's if you can find a tech to come out and diagnose it properly.
If I lived in the deep south, I'd get whatever the standard equipment is and spend the difference on extra solar panels.
I have my EPA cert, and I'd still probably go that route. The recovery pumps are expensive ($500+) and you need a recovery tank ($100), and then you still need to find somewhere that will take it from you. For a single job, it might be better to pay a HVAC company/moonlighting tech to do that part and do all the manual labor yourself.
There are lots of variables, but return on investment in solar is around 14% annually for me. It'll vary from place to place, so you need to do your own math.
It is interesting how the numbers work out in different places. Where I'm at it doesn't make sense at all. So much of my bill is just to have a meter and the per kilowatt rate is crazy low. Because of the high fee just to be hooked up the only way solar wins here is to get off grid - but winter kills that idea.
(I know everyone is expecting the entire grid to be 100% renewable on electric but it's going to take decades and by that time people can switch to new heat pumps. In the meantime we can save energy that way.)
(Also, which is more likely in ten years: that natural gas will be cheaper than today, or that electricity will be? I think with the huge new investments in renewables, the latter is more likely.)
Where I live electricity has been getting cheaper faster than natural gas, so at some point it makes more sense to do a heat pump.
Plus if natural gas is cheap it can also be used to generate electricity without having to run and maintain natural gas lines to every house as well as electrical lines.
It's recently become so high, I wonder if it's more economical to run hybrid cars on gas instead of charging them.
Therefore the choice is between a gas furnace at 90%, or gas to electricity to a heat pump at 150%, if we care about the efficiency of gas usage between the two options.
But when comparing price per kWh of delivered gas vs electricity, ignore the 50% gas-to-electricity efficiency, because that's irrelevant. It's just the 90% vs 300%.
Therefore a gas furnace is cheaper if the delivered price per kWh of gas happens to be no more than 30% that of electricity in your area. Of course the rate for gas will more likely be in therms than kWh, but that's a simple conversion (1 therm = 29.3 kWh).
I suppose that's the case in Texas?
> if natural gas is cheap it can also be used to generate electricity without having to run and maintain natural gas lines to every house
This holds true even if your current electricity mix involves coal or other things worse than natural gas. Those plants will have to be shut down within the lifetime of your appliance or neither thing matters very much.
[0]: https://afdc.energy.gov/fuels/natural_gas_renewable.html
However, our main motivation was to stop destroying the planet. Also within ~25 years, the government will require every building to be disconnected from gas (to achieve CO2 reduction goals). And from 2026 onwards, gas heating can still be installed, but it it'll be required to install a hybrid heat pump as well (a lower-capacity heat pump, where the gas furnace is a backup).
Where I live, driving a heat pump is more expensive than burning gas, from a purely economical POV. Our cost ratio per kW/h for electricity:gas is 3.5:1 right now, but COP for consumer heat pumps in real-world usage is just 2.6 (Yeah they all claim a COP of at least 3, but those are as realistic as ICE fuel economy ratings.) Those ratios need to at least match in order for a heat pump to make any kind of financial sense.
Those heat pumps for a mid sized house cost €15k right now. On back order for 12+ months.
https://www.sciencedirect.com/science/article/pii/S037877882...
Gas isn't 100% efficient either in heating the home. Boilers are ~92%.
E.g. you can either burn natural gas directly, or use electricity the Utility generated by burning natural gas. Or even Coal in many cases.
But that’s speaking more to the impact today. In the long run electrification across the board is required to reduce emissions.
https://www.statista.com/statistics/1234896/austria-distribu....
The US is still 60% Natural Gas + Coal https://www.statista.com/statistics/528603/distribution-elec...
There are plenty of US climates that’d do just fine with a modern heat pump system. This wasn’t always the case admittedly, due to the lower lows. I know it’s a meme at this point, but even on HN I still see a lot of distinctly American ignorance and exceptionalism when people talk about this. I’m thankful for Technology Connections et al for putting the hard yards into getting some nerd circles across the line.
We bought a heat pump last year and we're pretty happy with it. The cost is comparable to our older (not very efficient) gas furnace. Temperatures here (Vancouver, BC) rarely dip below zero Celsius.
I absolutely LOVE the Bosch system. It somehow manages to keep the heat more consistent at the set temp than my previous system. The Bosch system supposedly has some sort of power saving feature. We shall see how it handles the California summer.
As the adage goes, install quality is more important than the unit itself but so far I'm really impressed with the Bosch unit.
https://youtu.be/watch?v=-vU9x3dFMrU
Ref:
https://yaleclimateconnections.org/2023/02/how-heat-pumps-of...
- SCOP: 3.88
- kWh used: 525 kWh
- kWh produced: 2034.8 kWh
- Outside min: -11.4
- …max: 5.65
- …mean: 0.3
Dunno how far down insects and mouses live?
In the article they mention heating the ground with 1.5m deep holes. I guess that would annoy the local life?
And boom, there’s the problem. I have a heat pump for some bedrooms on the second floor but only because I have furnaces heating the other side. I am impressed how the tech has improved though.
And at this point in time, the best air-source heat pumps are good enough until -25C. Meaning that you get CoP more than 1 at this temperature. So this would work for most of the US just fine.
The most common heap pumps use bore holes straight down into the rock here in Sweden, but lateral installs are marginally better performance (sun reheats soil every summer) if you have a big garden.
Heap pumps dominate in Sweden so the installers have a lot of confidence and give good practical advise.
Many other units have auxillary resistive heating when the temperature are that low, which is obviously less efficient than the heat pump, but is still better than needing to maintain a fossil-fuel furnace.
Even in Canada, though, I'd look into whether heat pumps with resistive auxillary heat are economical. If it only ever goes below -20⁰F for, say, a week a year, you'd probably still come out on top. And you'd definitely come out on top environmentally if your electricity is mostly green.
The cheapest aux heat is to buy a bunch of space heaters.
Aux heat for heat pumps (not mini splits) usually starts at 5KW (4 space heaters) and is a dedicated circuit direct to the panel and sized correctly. It's also contained in a steel enclosure with strict rules about distances to flammable items.
As Lord Kelvin didn't become Lord Kelvin until 1892, it was thus a young, 28yo Professor William Thompson that made this proposal.
Valliant's pump is pretty quiet (I've heard PCs with worse fans) and uses a relatively benign refrigerant.
I think by and large, it's more quiet than the gas furnace we had before.
Does anyone know if heat pump outdoor units are audible?
If you can find the detailed spec sheet or service manual for the unit, they usually have decibal ratings listed.
This doesn’t make any sense: heat pumps adjust seamlessly for changing conditions and the low temperature ranges keep pushing more and more of the country into the range where you can go all winter without auxiliary heat. A few days of electric heat per year are nothing compared to the savings the rest of the time.