The heat pump was the only source of heat in this Vermont home, and it was seen to deliver 15,000 Btu/h at –15°F, very similar to the capacity provided by the manufacturer. At most other sites, heat pumps were operated as supplemental heat sources. In very cold conditions, auxiliary systems provided most (or in some cases all) of the heating.
At Site 4, for instance, a Mitsubishi FE18 operated at COPs of 1.5–2.0 at outdoor temperatures of –10°F. The FE18 at Site 1, by contrast, operated at COPs of 1.0–1.2 at outdoor temperatures between 0°F and 5°F.
So yeah, going 100% air-source heat pump if you’re area regularly spends time around -30°C (-22F) might not be the best idea. Though even the last report you cited said it might be 1.5-2x as efficient as resistive heating. And that Site 1 with bad COPs was because they manually lowered the fan speed…
There are vanishingly few people who live in areas with weather consistently below -30C. I’ve been seeing that kind of concern trolling all over the place in the past year or so, and they always have the same song and dance about low efficiency in extreme cold - technically correct, but taken as part of the bigger context, so niche as to be practically irrelevant. Yeah, if you live in Yakutsk you won’t want to rely only on a heat pump. Big fuckin’ deal - the other 99.5% of people on earth can benefit greatly.
Edit: I wouldn’t be susprised if this is the exact same guy I once argued with on Mastodon, actually. He was German too.
The efficiency isn’t the only problem limiting colder climates, it’s the need to periodically defrost the outdoor coils. This process generally occurs by running the normal air conditioning (cooling) mode, which can increase occupant discomfort. There is a point where this breaks down before the COP decreases.
But only for the 4 weeks a year you spend in unusually cold weather, the other 48 it’s more efficient.
It’s not like truly arctic places are a reasonable application but the overwhelming majority of our population lives south of Quebec and north of Wellington. So it’s not a relevant point, everyone in the Arctic can just use resistive heating or burn fuel, and if we get everything else on heat pumps we reduce our enegy use by a factor of 2-3 regardles.
Sure, for a few days a year it might get as bad as resistive heating. How horrible! So you don’t get 3.2x total throughout the year, you get 3.1x. It’s a non-issue.
I’ll chime in here since I own 2 heat pumps and live in a cold climate (often below 20C). Our house is heated with 100% electricity and after installing heat pumps our power bill dropped by about 18%. That includes all electricity, not just heating, so the gain in heating efficiency was very considerable.
I’m a very big proponent of heat pumps. The original post I responded to simply said all you need to do is bury the lines, which I wanted to clarify was not the only factor to consider.
Generally, cold climate heat pumps are an efficient source of heat down to -15 degrees Fahrenheit
“Generally” is the wrong way to approach this. What you should be looking at is the specific capabilities of the actual system that you are considering installing. Some of them can go much colder.
If the Mitsubishi FE18 isn’t efficient in your climate… then don’t buy that unit. Simple.
If it’s really cold where you are… then you could consider a ground source heat pump instead one that uses air as a heat source. The ground doesn’t get anywhere near cold to have efficiency issues no matter where you are in the world and ground source heat pumps don’t cost all that much… though they do require a bit of digging.
Also, if your heat pump is inefficient for a couple really cold weeks a year… oh well. You’re still coming out ahead because it’s very efficient the other 50 weeks a year. It’s not like they stop working at extremely cold temperatures, they just produce a bit less heat than you might like for the amount of power consumed. Maybe they’re “only” 80% efficient instead of 600% efficient… you know what else is 80% efficient? Heating with gas.
The UK is not what would be considered a cold climate. Also:
https://www.consumerreports.org/heat-pumps/can-heat-pumps-actually-work-in-cold-climates-a4929629430/
https://news.energysage.com/heat-pumps-cold-climates/
https://www1.eere.energy.gov/buildings/publications/pdfs/building_america/inverter-driven-heat-pumps-cold.pdf
So yeah, going 100% air-source heat pump if you’re area regularly spends time around -30°C (-22F) might not be the best idea. Though even the last report you cited said it might be 1.5-2x as efficient as resistive heating. And that Site 1 with bad COPs was because they manually lowered the fan speed…
There are vanishingly few people who live in areas with weather consistently below -30C. I’ve been seeing that kind of concern trolling all over the place in the past year or so, and they always have the same song and dance about low efficiency in extreme cold - technically correct, but taken as part of the bigger context, so niche as to be practically irrelevant. Yeah, if you live in Yakutsk you won’t want to rely only on a heat pump. Big fuckin’ deal - the other 99.5% of people on earth can benefit greatly.
Edit: I wouldn’t be susprised if this is the exact same guy I once argued with on Mastodon, actually. He was German too.
The efficiency isn’t the only problem limiting colder climates, it’s the need to periodically defrost the outdoor coils. This process generally occurs by running the normal air conditioning (cooling) mode, which can increase occupant discomfort. There is a point where this breaks down before the COP decreases.
Get a heat pump with resistive (electric) defrosting, not one that defrosts by running like an AC.
This kills your COP, making it inefficient.
But only for the 4 weeks a year you spend in unusually cold weather, the other 48 it’s more efficient.
It’s not like truly arctic places are a reasonable application but the overwhelming majority of our population lives south of Quebec and north of Wellington. So it’s not a relevant point, everyone in the Arctic can just use resistive heating or burn fuel, and if we get everything else on heat pumps we reduce our enegy use by a factor of 2-3 regardles.
Right. It depends on your climate.
Sure, for a few days a year it might get as bad as resistive heating. How horrible! So you don’t get 3.2x total throughout the year, you get 3.1x. It’s a non-issue.
I’ll chime in here since I own 2 heat pumps and live in a cold climate (often below 20C). Our house is heated with 100% electricity and after installing heat pumps our power bill dropped by about 18%. That includes all electricity, not just heating, so the gain in heating efficiency was very considerable.
20C is not a cold climate. If you mean -20, that’s not a cold climate either…
That’s literally the point where they start having problems, if you bothered reading my other post.
Removed by mod
Your behavior is completely out of line.
I’m a very big proponent of heat pumps. The original post I responded to simply said all you need to do is bury the lines, which I wanted to clarify was not the only factor to consider.
The Guardian is a UK publication.
Ok? The article talks about the rest of Europe, of which their are numerous countries that are actually in colder climates.
“Generally” is the wrong way to approach this. What you should be looking at is the specific capabilities of the actual system that you are considering installing. Some of them can go much colder.
If the Mitsubishi FE18 isn’t efficient in your climate… then don’t buy that unit. Simple.
If it’s really cold where you are… then you could consider a ground source heat pump instead one that uses air as a heat source. The ground doesn’t get anywhere near cold to have efficiency issues no matter where you are in the world and ground source heat pumps don’t cost all that much… though they do require a bit of digging.
Also, if your heat pump is inefficient for a couple really cold weeks a year… oh well. You’re still coming out ahead because it’s very efficient the other 50 weeks a year. It’s not like they stop working at extremely cold temperatures, they just produce a bit less heat than you might like for the amount of power consumed. Maybe they’re “only” 80% efficient instead of 600% efficient… you know what else is 80% efficient? Heating with gas.