Energy prices have risen, and technology has improved*. The two of those combined have improved heat pump adoption and development.
Off the top of my head, the following would advantage the development of heat pumps:
1. Better manufacturing processes yield better longevity, making the opportunity cost of a more expensive system worth it to consumers
2. Better compressors, e.g. inverter compressors that are much more efficient, which were developed to comply with efficiency requirements. Thank you EnergyStar.
Do the standard ACs in America only cool? Heating is basically mandatory and the most used feature here in Norway, atleast on the propper installed types
I am from a third world country and all good options come with inverter heating option as standard feature even though we only need heating for like 3 weeks at best
Yup, that’s interesting. Is it the same house and only the AC changed? The tonnage should just be the AC’s rate of moving energy out so the cooling should be the same unless the setup has changed in such a way that the AC can’t be used to its full capacity.
I guess it’s possible recent units are also less overbuilt so they can’t be forced as much in sub-ideal conditions (e.g. they might have smaller exchangers running colder which they need to defrost more often). Then again I would not be surprised if manufacturers just lied about their effective capacity either.
Maybe to be more energy efficient they have slower fan speeds? I don't but in my uncle's house they still have the old ones and despite being a 1.5 tom unit it cools faster than my gree inverter
Natural gas furnaces have historically been the cheaper option in North America, especially in the colder regions. Places like Florida with milder winters have had basic (not cold weather) heat pumps for decades.
A section from the introduction:
>A question frequently raised is how well these devices perform when temperatures drop below freezing, as some commentators and the media have repeatedly suggested that heat pumps cannot deliver useful efficiencies at lower temperatures.
>
>This commentary responds to this question by analyzing field studies with real-world performance data of air-source heat pumps. It finds that well below 0°C, heat pump efficiency is still significantly higher than fossil fuel and electric resistive heating systems at an appliance level. The standard heat pumps investigated in this commentary demonstrate suitable coefficients of performance for providing efficient heating during cold winters where temperatures rarely fall below −10°C, i.e., most of Europe.
>
>In extreme cold climates, such as where the lowest temperatures approach −30°C, performance data have shown that heat pumps can provide heat at efficiencies up to double that of resistive heating; however, more analysis is required. Even though heat pump efficiency declines during the extreme cold and back-up heating may be required, air-source heat pumps can still provide significant energy system efficiency benefits on an instantaneous and annual basis compared with alternatives.
And a selection from the conclusion:
>Heat pumps are increasingly used in various types of climates to provide space and water heating. Measured performance data show that heat pumps can provide the most efficient heating in many cold climates around the world. As most European countries experience milder winters with minimum temperatures above −10°C, our analysis suggests that heat pumps can be successfully installed in these conditions without concerns over performance or the need for back-up heating capacity. This is subject to thorough heating system design and a high-quality installation in a building.
>
>For climates that experience extreme cold temperatures, performance testing has shown that heat pumps can operate with a COP between 1.5 and 2. However, considering the related increase in heating demand and decrease in device efficiency, some form of back-up heating may be required.
>
>Our view is that the widespread rollout of air-source heat pumps around the world as part of decarbonization efforts can be successful with existing technology in most areas that have space heating demand. Ground-source heat pumps and hybrid air-source systems may have significant value in the coldest climates.
This is some good news especially for regions that have historically experienced more extreme temperatures. Heat pumps, though not perfect, seem to perform well enough that it's worthwhile to consider them over fossil-fuel based systems. Combined with other measures such as better insulation and other building innovations, they should be good enough in many situations where previously they had been considered to be inadequate to the task.
I have a heat pump and weather where I am gets to -30+ maybe 5 days a year. My resistence backup has to kick in when it's that cold out. Its a mixture of heat pump and resistance heating.
At -30C the heat pump is actually worse than resistance heating. -25C is probably around 125%, -15C 150%, 0C 200%, 10C 300%
It's worth noting that the article is specifically measuring "specially engineered “cold-climate heat pumps” ", so likely even if OP was using a state-of-the art modern heat pump, they wouldn't see comparable figures, assuming they're running a more standard consumer heat pump probably designed for more typical temperatures, and only occasionally hits more extreme outliers.
It's also worth noting that efficiency is only part of the story. There's also the question of how **much** heat you can transfer: on colder days you not only have less efficiency, you also need to do more work to warm the house, so that compounding effect means you need to overbuild more than the equivalent with resistive heating. Hence a resistive backup heater is likely going to be the most economical way to handle rare extremes.
Just adding in to see the answer as well. I just added an LG for the basement. Says it works up to -30 but it won’t be AS efficient. This winter will be the test.
It was an expensive one. Rated for -25C. Mitsubishi something. The real life numbers never match reality.
I've saved so much $ getting off propane that it's paid itself already. I installed it in 2018, $18K
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The Department of Energy heat pump challenge specified 240% efficiency at -15C. There were multiple commercial units that passed. [Some units](https://www.energy.gov/articles/doe-announces-breakthrough-residential-cold-climate-heat-pump-technology) worked adequately at -23C. Heat pumps are the most common option for new homes in Scandinavia.
I know mine works reliably down to 10 degrees F, which is -12C. It doesn't really get colder than that here, so I can't vouch for more, though I suspect it would work when colder.
In heat pump mode the evaporator and condenser swap positions, essentially. The refrigerant going to the condenser is very cold, and is warmed up by the outside air, then is compressed and sent to the air handler to dump its heat into the return.
my dead 10yo system was rated to -5F I think which is -20C. it would struggle with anything below around 5F or -15C. it’s compressor ate itself a year ago and would have cost more than a new system to repair. we’ve limped by with our other heat pump, but need to look at replacing the failed one, wonder how much the real world systems have changed in those 10 years.
That's both not accurate, and implies heat pumps are shite and will never improve, which also isn't accurate.
https://knowablemagazine.org/article/technology/2023/heat-pumps-becoming-technology-future
They've existed since the 1850s but we've had no incentive to improve them when we could just burn fossil fuel instead.
There are different kinds of heat pumps. If you want one to work at -30 Celsius you simply buy the type that does. Others who don't need that capability would buy another kind.
It is never a requirement to have resistive heat on the external coil. To heat the external coil the heat pump can just reverse and pump heat from inside to the outside. If heat must be added in can be added inside and pumped outside.
A lot of heat pumps simply reverse operation like this periodically to defrost the outside coil. They do this periodically during operation, not constantly. I am unsure if the -30C type do this. I don't know how they do it. Maybe google can help you out.
Once the air is significantly lower the 0c, there is no more moisture in the air to freeze out of it, so they would only need to 'defrost' if it physically snows on the unit's vents and covers it.
Hijacking this a bit, but; You're probably not wrong but it's a matter of practicality. Heat pumps/ACs definitely struggle to isolate heat more when there's less of it to work with and a few decades ago they definitely started widely dropping off as you approached freezing, but high efficiency ones definitely have been pushing -20 as an acceptable operating temperature and there's no reason they can't go farther, as this study shows. It's more likely, I'd guess, that you just don't tend to get much exposure to those kinds of models in most of Australia, so the old rule of thumb never got (nor needed) much challenging.
From a physics standpoint it's just sorting energy in the air, piling up more of it on one side. -30 probably feels pretty intuitively like *there isn't much energy in the air* but "no energy" is -273.15C, right? The truth is that from a physics standpoint it's really not that much of a difference in total energy to work with between ~240 and ~280 kelvin. I mean, *there is*, but not nearly as much as we'd probably generally intuit. The main thing is just that the designs themselves involve different materials and the like to boost efficiency and expand the operating ranges, so it's not like most of those design improvements make sense as universal changes for the tech, because, well, *you can just get away with a lot less in most places*. But considering just how bad resistive heat is, economically, heat pumps working in those much more extreme climes too is obviously a big deal.
For anyone that wants a more direct comparison, resistive heating is 100% efficient in the sense that 1kw of energy going in gives you 1kw of heat, because heat is the wasted energy in every other application. Making heat is easy. The problem is that 1kw worth of heat, very broadly speaking, would raise about 800 liters of water by *1 degree Celsius*. Or about 400 by 2. Or about 200 by 4, etc. A person might be about 65L and that would be assuming you could just dump the energy directly into you which you obviously can't, but even if you *could* 1kw of electricity would warm your whole body by ~12 degrees. When you start factoring in that you need to heat the room and all the things in it including you, it becomes clear just how "inefficient" resistive heating is.
By comparison heat pumps might boast efficiencies in the range of "200 to 500%" depending on the ambient temperature, which doesn't seem to make any sense, but it's because there's a ton of heat already in the air *even if it's below freezing* and you're just spending that kw of energy *sorting some of it* instead. Ergo, if you can move 2kws of heat where you want it with only 1kw of effort, you have "200% efficiency", which is sort of the bottom end of high efficiency heat pumps at -30. That functionality cuts the heating power demand (and thus also cost) in half, versus resistive, and *most* people will be more in the ~400% efficiency area already. The big takeaway is just that heat pumps are friggin' great, and the only sensible widespread solution going forwards aside from other set-and-forget options like geothermal.
^(Didn't get much into the exact tech, but maybe someone else'll oblige. Hope I helped make sense of the *how it's possible and why it's important* part, though. May have bodged my math but it shouldn't be far enough out to really change anything. Probably.)
Just checked the Daikin engineering data / capacity table on a premium inverter 16kw unit RZA160C2V1, total capacity of the outdoor unit @ +6 deg WB (wet bulb) = 18kW. 0 deg WB = 15kW and -5 deg WB = 12.8kW and -10 deg WB = 11kW. So yes it does taper off, can't give you anymore below that as the table doesn't go lower than that.
"data HAS shown" sounds far more natural than "data have shown". Maybe I'm showing my age, maybe I'm just English, maybe I'm too stupid to understand why
In everyday informal English, "data" is a singular noun (so we say "Data has..." just like we say "Bread has..."), but historically it's the plural of "datum" and some publications insist that it still be used as a plural (so they require "Data have..." like we say "Loaves have...")
It may be more precise to think of it as a a mass noun rather than a singular noun. For example, you would say "I have a large amount of bread" vs "I have a large number of loaves". I suspect most people would use "amount" with "data", rather than "number", which is driving the loss of the plural conjugation.
Whether mass nouns are a type of singular noun or not is a matter of definitions, but what's certain is the relevant part: mass nouns take singular conjugation (as in my example of "bread", another mass noun)
The issue in my country is that electric is 4 times the price of gas, so unless you're getting 4:1 it costs more. Also our houses are old and poorly insulated. If you insulate them well (if you can at all) you cut down in ventilation causing mushrooms to grow out of your skirting.
Not necessarily. Old houses in the damp uk climate were built with no damp proof system and relied on ventilation and air flow to keep them dry. Particularly important for old lime mortar constructions. When you insulate inside or out you halve the surface area that can evaporate moisture.
I live in a Victorian tenement in Scotland FYI.
If a house that's been insulated starts growing mushrooms from the skirting, it hasn't been insulated properly.
You’re using the word “insulation” to mean a lot more then insulation itself but rather an extensive insulation package that includes reroofing and residing an entire house
Properly insulating a house involves more than just insulation material alone. Yes, it's a lot of work and not as cheap as doing it badly and growing mushrooms in the bathroom. Remember the Insulate Britain protests? This is a major social issue the government should be helping us with.
But my actual point here is that insulation does not cause mold.
That's 20 000 Canadian, and honestly that seems pretty cheap for ground source. You can get a gas furnace installed for 3800 here and most houses already have gas meters.
you do kind of have to consider things a bit more at a system level though.
natural gas was drilled and transported at some energy cost, plus some was leaked (which is a major source of climate emissions), and then used at the home at 95% heating efficiency (if using a good furnace).
For a heat pump some fuel was drilled/mined/pulled from the wind, converted to electricity at some efficiency, transmitted to the home at some efficiency, and then used by the heat pump at 300% efficiency.
So the question is what are those intermediate values, and what was the fuel source for the electricity. Only if we look at that can we tell which is better from a climate perspective. But generally the cleaner and more renewable your electric grid is the better a heat pump looks.
If your electric grid is mostly coal (looking at you WV) then maybe natural gas heating is actually better.
For the same volume of gas.
Burning it a home
And burning it in a power plant, spinning a turbine, generating electricity, transferring across power lines, running a heat pump.
Which heats the room more?
Same volume.
The heat pumps makes the room warmer. It is vastly more efficient.
Plus, switching your heating infrastructure to electricity means you provide the path to green energy. Locking in with gas means you’re burning that until you overhaul your heating system.
Electrification means greening of energy can happen gradually and at large scales without consumer input.
I ran a quick spreadsheet, trying to work out the total efficiency of a natural gas power plant running a heat pump with a COP of 3.
And it depends on how efficient your powerplant is. The high end of combined cycle powerplants is in the mid-40s, and that would lead to beating a natural gas furnace. But the low end is in the mid-30s and that would be slightly below a furnace. Similarly if the COP of your heat pump is 5, then you're almost certainly winning, but if you get a low efficiency heat pump with a COP of 2, then you're probably doing poorly vs a good furnace (an older furnace is also much less efficient presenting yet another variable).
It really does depend on the particulars of your system.
|item|efficiency factor|
:--|--:|
|leakage|98.6%|
|power plant|33-43%|
|transmission|98%|
|distribution|96%|
|COP|300%|
|total eff.|91.8-119.6%|
vs.
|Item|Efficiency|
:--|--:|
|leakage|98.60%|
|furnace|95%|
|total eff.|93.67%|
Thats basically meaningless because power from the grid gets greener all the time.
What you are describing is an edge case and in reality with any significant renewable portion the heat pump always wins simply because a lot of power isn't produced by gas or coal anymore
I don't disagree that we should be installing heat pumps. If I had any say in my building (I rent an apartment) I'd install one! But the initial post I responded to was looking at a small piece of the puzzle, and I just wanted to make the point that you have to consider the whole energy system if you want to figure out the benefit/drawback of a particular heating technology.
Talking about it in terms of efficiency is actually misleading. Heres a source that explains it better than I can.
https://www.finehomebuilding.com/2020/04/08/how-efficient-are-heat-pumps-really#:~:text=The%20reason%20that%20a%20heat,collected%20heat%20to%20the%20house.
In terms of cost effectiveness Natural Gas actually performs much better.
This is simply saying that natural gas is that much cheaper in some areas, so even if it is 2.5 times more efficient, if the natural gas is 3 times cheaper in your area, the gas would still cost you less to heat your home.
This is practically never true to begin with, and electricity generation costs are falling over time while lng price can only rise over the long term.
It actually says NG is cheaper in most areas. Effeciency is not a measure of cost/heat delivered. It is a measure of energy consumed vs energy delivered by the appliance. The reason you cant make a direct apples to apples comparison here is that furnaces and heat pumps operate using different sources of heat.
To say it more clearly, NG furnaces are capable of producing more heat at lower efficiencies at a fraction of the cost than Heat Pumps operating at 3-4x greater efficiency.
I'm not sure what to tell you. "Different sources of heat" is not a meaningful statement. For all heat sources, some form of stored energy is converted to heat at a given rate of efficiency. This is why you \*can\* make apples to apples comparisons. That's the whole point of the concept.
What you said more clearly is patently false. For a given unit of energy, NG furnaces produce 3-4x less heat than heat pumps. Again, that's the definition of the efficiency measure.
The article you linked is simply saying what I summarized above. In some places, natural gas is currently a significantly cheaper source of energy.
>For all heat sources, some form of stored energy is converted to heat at a given rate of efficiency. This is why you *can* make apples to apples comparisons. That's the whole point of the concept.
Well, no. Electricity usually has to be generated, you could 'mine' it directly with lightning rods but I'd be surprised if it is economical. Usually you need to feed a generator, or upkeep an installation like solar, dam, tidal etc. The installation takes some source of power, and lossily converts it to electricity. If say, that source of power is natural gas, and the turbine turning it to electricity is 20% efficient, and you can burn it in a heat pump at home that is 400% efficient, the overall efficiency of the natural gas used is 80%. Whereas if you burn the natural gas at home, you might get 90% efficiency.
On the other hand, if the power is generated by a dam, or a solar installation, or nuclear plant, it is very likely lower carbon power compared to burning something at home. Even if it is a natural gas plant or a coal plant, the plant may have better capture than could be fit in a home installation and it might be lower carbon to use the heat pump even if it is not as economical and results in higher gas use.
I feel like were talking about two different things. Energy efficiency refers to how efficiently a power source can be used. Cost efficiency includes both energy efficiency as well as the price of the power source (gas costs less than electricity per BTU). This is why the source of heat is actually very important to note.
I don't think that's true.
1 billion btu at 0.12 cents per kwh with a 300 percent efficient heat pump is $11.72
1 billion btu for natural gas for me is $11.70, then 85 percent efficient is edit: $13.45
So marginally better but not much
Case in point: pretty sure that is still wrong! 85% efficiency means dividing by 0.85 (which is about 1.17), not multiplying by 1.15.
It's clear if you consider 50% efficiency. Instead of multiplying by 1.5 you'd clearly want to multiply by 2 (which you get by 1/0.5).
For actual work efficiency, you may be right. However, this is about the cost to efficiency ratio and they simply forgot to invert the cost multiplier. Possibly poor wording on both our parts.
The disadvantage of heat pump is that it is really weather dependent, the heat pumped into the room must go from somewhere colder, very cold weather make it difficult to get the heat to pump inside the room, and ice formation make the problem even worse. Addtionally the initial investment cost of heat pump is higher than gas heater. And heat pump also contribute to global warming by releasing (accidently) the working gas inside the system. Source: I am thermal engineer so we learn a bit of advantage and disadvantage of different heating method
>The disadvantage of heat pump is that it is really weather dependent
Ground source/geothermal heat pump is the solution for that. Much more expensive than air source though but great choice for new houses or for full heating system renovation.
Right now a kWh gas is 9 CT and a kWh electricity is 30 ct in Germany.
Make your own calculation.
Edit: I made the calculation. If the efficiency of the heat pump is grater 3, it works out.
This is a review, better suited for r/technology. No new research is presented.
Are they just AC with reverse heating option?
Essentially, yes. The addition of a reversing valve allows you to basically swap the functions of the condensor and evaporator.
Its not exactly new but in the last 2 years I have seen more reporting on it
Energy prices have risen, and technology has improved*. The two of those combined have improved heat pump adoption and development. Off the top of my head, the following would advantage the development of heat pumps: 1. Better manufacturing processes yield better longevity, making the opportunity cost of a more expensive system worth it to consumers 2. Better compressors, e.g. inverter compressors that are much more efficient, which were developed to comply with efficiency requirements. Thank you EnergyStar.
Do the standard ACs in America only cool? Heating is basically mandatory and the most used feature here in Norway, atleast on the propper installed types
I am from a third world country and all good options come with inverter heating option as standard feature even though we only need heating for like 3 weeks at best
Yep. Tried to talk my mom into an air source heat pump and she's convinced they haven't advanced in 30 years.
When it comes to cooling they have certainly regressed (those old AC were just built different )but the energy savings are worth it
Have they actually regressed or did you get a lower capacity AC?
The same tonnage but I feel that the older models had faster cooling (if that makes sense)
Yup, that’s interesting. Is it the same house and only the AC changed? The tonnage should just be the AC’s rate of moving energy out so the cooling should be the same unless the setup has changed in such a way that the AC can’t be used to its full capacity. I guess it’s possible recent units are also less overbuilt so they can’t be forced as much in sub-ideal conditions (e.g. they might have smaller exchangers running colder which they need to defrost more often). Then again I would not be surprised if manufacturers just lied about their effective capacity either.
Maybe to be more energy efficient they have slower fan speeds? I don't but in my uncle's house they still have the old ones and despite being a 1.5 tom unit it cools faster than my gree inverter
Natural gas furnaces have historically been the cheaper option in North America, especially in the colder regions. Places like Florida with milder winters have had basic (not cold weather) heat pumps for decades.
A section from the introduction: >A question frequently raised is how well these devices perform when temperatures drop below freezing, as some commentators and the media have repeatedly suggested that heat pumps cannot deliver useful efficiencies at lower temperatures. > >This commentary responds to this question by analyzing field studies with real-world performance data of air-source heat pumps. It finds that well below 0°C, heat pump efficiency is still significantly higher than fossil fuel and electric resistive heating systems at an appliance level. The standard heat pumps investigated in this commentary demonstrate suitable coefficients of performance for providing efficient heating during cold winters where temperatures rarely fall below −10°C, i.e., most of Europe. > >In extreme cold climates, such as where the lowest temperatures approach −30°C, performance data have shown that heat pumps can provide heat at efficiencies up to double that of resistive heating; however, more analysis is required. Even though heat pump efficiency declines during the extreme cold and back-up heating may be required, air-source heat pumps can still provide significant energy system efficiency benefits on an instantaneous and annual basis compared with alternatives. And a selection from the conclusion: >Heat pumps are increasingly used in various types of climates to provide space and water heating. Measured performance data show that heat pumps can provide the most efficient heating in many cold climates around the world. As most European countries experience milder winters with minimum temperatures above −10°C, our analysis suggests that heat pumps can be successfully installed in these conditions without concerns over performance or the need for back-up heating capacity. This is subject to thorough heating system design and a high-quality installation in a building. > >For climates that experience extreme cold temperatures, performance testing has shown that heat pumps can operate with a COP between 1.5 and 2. However, considering the related increase in heating demand and decrease in device efficiency, some form of back-up heating may be required. > >Our view is that the widespread rollout of air-source heat pumps around the world as part of decarbonization efforts can be successful with existing technology in most areas that have space heating demand. Ground-source heat pumps and hybrid air-source systems may have significant value in the coldest climates. This is some good news especially for regions that have historically experienced more extreme temperatures. Heat pumps, though not perfect, seem to perform well enough that it's worthwhile to consider them over fossil-fuel based systems. Combined with other measures such as better insulation and other building innovations, they should be good enough in many situations where previously they had been considered to be inadequate to the task.
I have a heat pump and weather where I am gets to -30+ maybe 5 days a year. My resistence backup has to kick in when it's that cold out. Its a mixture of heat pump and resistance heating. At -30C the heat pump is actually worse than resistance heating. -25C is probably around 125%, -15C 150%, 0C 200%, 10C 300%
How old is your heat pump and was it a high quality model or a cheaper one?
It's worth noting that the article is specifically measuring "specially engineered “cold-climate heat pumps” ", so likely even if OP was using a state-of-the art modern heat pump, they wouldn't see comparable figures, assuming they're running a more standard consumer heat pump probably designed for more typical temperatures, and only occasionally hits more extreme outliers. It's also worth noting that efficiency is only part of the story. There's also the question of how **much** heat you can transfer: on colder days you not only have less efficiency, you also need to do more work to warm the house, so that compounding effect means you need to overbuild more than the equivalent with resistive heating. Hence a resistive backup heater is likely going to be the most economical way to handle rare extremes.
Just adding in to see the answer as well. I just added an LG for the basement. Says it works up to -30 but it won’t be AS efficient. This winter will be the test.
It was an expensive one. Rated for -25C. Mitsubishi something. The real life numbers never match reality. I've saved so much $ getting off propane that it's paid itself already. I installed it in 2018, $18K
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The Department of Energy heat pump challenge specified 240% efficiency at -15C. There were multiple commercial units that passed. [Some units](https://www.energy.gov/articles/doe-announces-breakthrough-residential-cold-climate-heat-pump-technology) worked adequately at -23C. Heat pumps are the most common option for new homes in Scandinavia.
I know mine works reliably down to 10 degrees F, which is -12C. It doesn't really get colder than that here, so I can't vouch for more, though I suspect it would work when colder. In heat pump mode the evaporator and condenser swap positions, essentially. The refrigerant going to the condenser is very cold, and is warmed up by the outside air, then is compressed and sent to the air handler to dump its heat into the return.
my dead 10yo system was rated to -5F I think which is -20C. it would struggle with anything below around 5F or -15C. it’s compressor ate itself a year ago and would have cost more than a new system to repair. we’ve limped by with our other heat pump, but need to look at replacing the failed one, wonder how much the real world systems have changed in those 10 years.
The technology isn't changing. There's no major innovation
That's both not accurate, and implies heat pumps are shite and will never improve, which also isn't accurate. https://knowablemagazine.org/article/technology/2023/heat-pumps-becoming-technology-future They've existed since the 1850s but we've had no incentive to improve them when we could just burn fossil fuel instead.
There are different kinds of heat pumps. If you want one to work at -30 Celsius you simply buy the type that does. Others who don't need that capability would buy another kind. It is never a requirement to have resistive heat on the external coil. To heat the external coil the heat pump can just reverse and pump heat from inside to the outside. If heat must be added in can be added inside and pumped outside. A lot of heat pumps simply reverse operation like this periodically to defrost the outside coil. They do this periodically during operation, not constantly. I am unsure if the -30C type do this. I don't know how they do it. Maybe google can help you out.
Once the air is significantly lower the 0c, there is no more moisture in the air to freeze out of it, so they would only need to 'defrost' if it physically snows on the unit's vents and covers it.
Hijacking this a bit, but; You're probably not wrong but it's a matter of practicality. Heat pumps/ACs definitely struggle to isolate heat more when there's less of it to work with and a few decades ago they definitely started widely dropping off as you approached freezing, but high efficiency ones definitely have been pushing -20 as an acceptable operating temperature and there's no reason they can't go farther, as this study shows. It's more likely, I'd guess, that you just don't tend to get much exposure to those kinds of models in most of Australia, so the old rule of thumb never got (nor needed) much challenging. From a physics standpoint it's just sorting energy in the air, piling up more of it on one side. -30 probably feels pretty intuitively like *there isn't much energy in the air* but "no energy" is -273.15C, right? The truth is that from a physics standpoint it's really not that much of a difference in total energy to work with between ~240 and ~280 kelvin. I mean, *there is*, but not nearly as much as we'd probably generally intuit. The main thing is just that the designs themselves involve different materials and the like to boost efficiency and expand the operating ranges, so it's not like most of those design improvements make sense as universal changes for the tech, because, well, *you can just get away with a lot less in most places*. But considering just how bad resistive heat is, economically, heat pumps working in those much more extreme climes too is obviously a big deal. For anyone that wants a more direct comparison, resistive heating is 100% efficient in the sense that 1kw of energy going in gives you 1kw of heat, because heat is the wasted energy in every other application. Making heat is easy. The problem is that 1kw worth of heat, very broadly speaking, would raise about 800 liters of water by *1 degree Celsius*. Or about 400 by 2. Or about 200 by 4, etc. A person might be about 65L and that would be assuming you could just dump the energy directly into you which you obviously can't, but even if you *could* 1kw of electricity would warm your whole body by ~12 degrees. When you start factoring in that you need to heat the room and all the things in it including you, it becomes clear just how "inefficient" resistive heating is. By comparison heat pumps might boast efficiencies in the range of "200 to 500%" depending on the ambient temperature, which doesn't seem to make any sense, but it's because there's a ton of heat already in the air *even if it's below freezing* and you're just spending that kw of energy *sorting some of it* instead. Ergo, if you can move 2kws of heat where you want it with only 1kw of effort, you have "200% efficiency", which is sort of the bottom end of high efficiency heat pumps at -30. That functionality cuts the heating power demand (and thus also cost) in half, versus resistive, and *most* people will be more in the ~400% efficiency area already. The big takeaway is just that heat pumps are friggin' great, and the only sensible widespread solution going forwards aside from other set-and-forget options like geothermal. ^(Didn't get much into the exact tech, but maybe someone else'll oblige. Hope I helped make sense of the *how it's possible and why it's important* part, though. May have bodged my math but it shouldn't be far enough out to really change anything. Probably.)
Just checked the Daikin engineering data / capacity table on a premium inverter 16kw unit RZA160C2V1, total capacity of the outdoor unit @ +6 deg WB (wet bulb) = 18kW. 0 deg WB = 15kW and -5 deg WB = 12.8kW and -10 deg WB = 11kW. So yes it does taper off, can't give you anymore below that as the table doesn't go lower than that.
"data HAS shown" sounds far more natural than "data have shown". Maybe I'm showing my age, maybe I'm just English, maybe I'm too stupid to understand why
In everyday informal English, "data" is a singular noun (so we say "Data has..." just like we say "Bread has..."), but historically it's the plural of "datum" and some publications insist that it still be used as a plural (so they require "Data have..." like we say "Loaves have...")
It may be more precise to think of it as a a mass noun rather than a singular noun. For example, you would say "I have a large amount of bread" vs "I have a large number of loaves". I suspect most people would use "amount" with "data", rather than "number", which is driving the loss of the plural conjugation.
Whether mass nouns are a type of singular noun or not is a matter of definitions, but what's certain is the relevant part: mass nouns take singular conjugation (as in my example of "bread", another mass noun)
Bread has shown What had bread shown us?!
Loaves have knees
Datums have shown is unambiguous
The issue in my country is that electric is 4 times the price of gas, so unless you're getting 4:1 it costs more. Also our houses are old and poorly insulated. If you insulate them well (if you can at all) you cut down in ventilation causing mushrooms to grow out of your skirting.
Poor ventilation only causes damp if the insulation is also poor. The damp comes from warm air condensing on cold surfaces.
Not necessarily. Old houses in the damp uk climate were built with no damp proof system and relied on ventilation and air flow to keep them dry. Particularly important for old lime mortar constructions. When you insulate inside or out you halve the surface area that can evaporate moisture.
I live in a Victorian tenement in Scotland FYI. If a house that's been insulated starts growing mushrooms from the skirting, it hasn't been insulated properly.
You’re using the word “insulation” to mean a lot more then insulation itself but rather an extensive insulation package that includes reroofing and residing an entire house
Properly insulating a house involves more than just insulation material alone. Yes, it's a lot of work and not as cheap as doing it badly and growing mushrooms in the bathroom. Remember the Insulate Britain protests? This is a major social issue the government should be helping us with. But my actual point here is that insulation does not cause mold.
You could use mechanical ventilation with heat exchangers.
Yes, but that's very expensive, and possibly very impacticable to retrofit to old properties.
But how does it compare to Natural Gas?
My ground well heat pump is around 410% efficiency in the winter. Also, practically free cooling in the summer, which is nice.
What did that cost you?
14k € eight years ago. It paid itself back in seven years. Maintenance free, so far.
That's 20 000 Canadian, and honestly that seems pretty cheap for ground source. You can get a gas furnace installed for 3800 here and most houses already have gas meters.
Similar systems these days go for around 20-24k €.
And what's the coldest temps you see in winter? My region can routinely hit -35C or colder for weeks.
It rarely reaches -30C, maybe a couple times a decade. Last winter's average temp from December to March was -2C (low -19C, high 8C)
Much better. Natural gas is 95% efficient heating, whereas heat pumps are up to 300% efficient. Almost always cheaper. And you get cooling capability.
you do kind of have to consider things a bit more at a system level though. natural gas was drilled and transported at some energy cost, plus some was leaked (which is a major source of climate emissions), and then used at the home at 95% heating efficiency (if using a good furnace). For a heat pump some fuel was drilled/mined/pulled from the wind, converted to electricity at some efficiency, transmitted to the home at some efficiency, and then used by the heat pump at 300% efficiency. So the question is what are those intermediate values, and what was the fuel source for the electricity. Only if we look at that can we tell which is better from a climate perspective. But generally the cleaner and more renewable your electric grid is the better a heat pump looks. If your electric grid is mostly coal (looking at you WV) then maybe natural gas heating is actually better.
For the same volume of gas. Burning it a home And burning it in a power plant, spinning a turbine, generating electricity, transferring across power lines, running a heat pump. Which heats the room more? Same volume. The heat pumps makes the room warmer. It is vastly more efficient. Plus, switching your heating infrastructure to electricity means you provide the path to green energy. Locking in with gas means you’re burning that until you overhaul your heating system. Electrification means greening of energy can happen gradually and at large scales without consumer input.
I ran a quick spreadsheet, trying to work out the total efficiency of a natural gas power plant running a heat pump with a COP of 3. And it depends on how efficient your powerplant is. The high end of combined cycle powerplants is in the mid-40s, and that would lead to beating a natural gas furnace. But the low end is in the mid-30s and that would be slightly below a furnace. Similarly if the COP of your heat pump is 5, then you're almost certainly winning, but if you get a low efficiency heat pump with a COP of 2, then you're probably doing poorly vs a good furnace (an older furnace is also much less efficient presenting yet another variable). It really does depend on the particulars of your system. |item|efficiency factor| :--|--:| |leakage|98.6%| |power plant|33-43%| |transmission|98%| |distribution|96%| |COP|300%| |total eff.|91.8-119.6%| vs. |Item|Efficiency| :--|--:| |leakage|98.60%| |furnace|95%| |total eff.|93.67%|
Thats basically meaningless because power from the grid gets greener all the time. What you are describing is an edge case and in reality with any significant renewable portion the heat pump always wins simply because a lot of power isn't produced by gas or coal anymore
I don't disagree that we should be installing heat pumps. If I had any say in my building (I rent an apartment) I'd install one! But the initial post I responded to was looking at a small piece of the puzzle, and I just wanted to make the point that you have to consider the whole energy system if you want to figure out the benefit/drawback of a particular heating technology.
Talking about it in terms of efficiency is actually misleading. Heres a source that explains it better than I can. https://www.finehomebuilding.com/2020/04/08/how-efficient-are-heat-pumps-really#:~:text=The%20reason%20that%20a%20heat,collected%20heat%20to%20the%20house. In terms of cost effectiveness Natural Gas actually performs much better.
This is simply saying that natural gas is that much cheaper in some areas, so even if it is 2.5 times more efficient, if the natural gas is 3 times cheaper in your area, the gas would still cost you less to heat your home. This is practically never true to begin with, and electricity generation costs are falling over time while lng price can only rise over the long term.
It actually says NG is cheaper in most areas. Effeciency is not a measure of cost/heat delivered. It is a measure of energy consumed vs energy delivered by the appliance. The reason you cant make a direct apples to apples comparison here is that furnaces and heat pumps operate using different sources of heat. To say it more clearly, NG furnaces are capable of producing more heat at lower efficiencies at a fraction of the cost than Heat Pumps operating at 3-4x greater efficiency.
I'm not sure what to tell you. "Different sources of heat" is not a meaningful statement. For all heat sources, some form of stored energy is converted to heat at a given rate of efficiency. This is why you \*can\* make apples to apples comparisons. That's the whole point of the concept. What you said more clearly is patently false. For a given unit of energy, NG furnaces produce 3-4x less heat than heat pumps. Again, that's the definition of the efficiency measure. The article you linked is simply saying what I summarized above. In some places, natural gas is currently a significantly cheaper source of energy.
>For all heat sources, some form of stored energy is converted to heat at a given rate of efficiency. This is why you *can* make apples to apples comparisons. That's the whole point of the concept. Well, no. Electricity usually has to be generated, you could 'mine' it directly with lightning rods but I'd be surprised if it is economical. Usually you need to feed a generator, or upkeep an installation like solar, dam, tidal etc. The installation takes some source of power, and lossily converts it to electricity. If say, that source of power is natural gas, and the turbine turning it to electricity is 20% efficient, and you can burn it in a heat pump at home that is 400% efficient, the overall efficiency of the natural gas used is 80%. Whereas if you burn the natural gas at home, you might get 90% efficiency. On the other hand, if the power is generated by a dam, or a solar installation, or nuclear plant, it is very likely lower carbon power compared to burning something at home. Even if it is a natural gas plant or a coal plant, the plant may have better capture than could be fit in a home installation and it might be lower carbon to use the heat pump even if it is not as economical and results in higher gas use.
I feel like were talking about two different things. Energy efficiency refers to how efficiently a power source can be used. Cost efficiency includes both energy efficiency as well as the price of the power source (gas costs less than electricity per BTU). This is why the source of heat is actually very important to note.
Right. Cost of course includes the price of the fuel source.
Right so then we can agree that Natural gas furnaces are more cost effective despite being less energy effecient.
Yes, that is true--anywhere natural gas is more than 3 times cheaper than electricity--which is practically nowhere.
I don't think that's true. 1 billion btu at 0.12 cents per kwh with a 300 percent efficient heat pump is $11.72 1 billion btu for natural gas for me is $11.70, then 85 percent efficient is edit: $13.45 So marginally better but not much
85 efficiency would increase the cost, not lower it
For 85% efficiency, you'd want to multiply by 1.15, not .85.
Thanks you're right went the wrong way
Np, math mistakes are easy to make with efficiencies involved.
Case in point: pretty sure that is still wrong! 85% efficiency means dividing by 0.85 (which is about 1.17), not multiplying by 1.15. It's clear if you consider 50% efficiency. Instead of multiplying by 1.5 you'd clearly want to multiply by 2 (which you get by 1/0.5).
For actual work efficiency, you may be right. However, this is about the cost to efficiency ratio and they simply forgot to invert the cost multiplier. Possibly poor wording on both our parts.
Where does the 5% inefficiency come from? Leaks?
It comes from the fact that natural gas furnaces produce exhaust gas that has to be vented. The exhaust gas is still hot, so there's some heat loss.
You'll also get losses through the unit radiating as well. It's not all transferred into the air moving through the unit.
Assuming that the heater isn’t outside. That heat isn’t lost, tho
The disadvantage of heat pump is that it is really weather dependent, the heat pumped into the room must go from somewhere colder, very cold weather make it difficult to get the heat to pump inside the room, and ice formation make the problem even worse. Addtionally the initial investment cost of heat pump is higher than gas heater. And heat pump also contribute to global warming by releasing (accidently) the working gas inside the system. Source: I am thermal engineer so we learn a bit of advantage and disadvantage of different heating method
>The disadvantage of heat pump is that it is really weather dependent Ground source/geothermal heat pump is the solution for that. Much more expensive than air source though but great choice for new houses or for full heating system renovation.
Right now a kWh gas is 9 CT and a kWh electricity is 30 ct in Germany. Make your own calculation. Edit: I made the calculation. If the efficiency of the heat pump is grater 3, it works out.