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No, they don’t. Below 20ish degrees they are worthless.
It doesn’t get bitter BITTER cold here but sometimes it does and half the city
without gas freezes.
I live in the south and it rarely gets that cold here. I often wondered why the high pressure side wasn't used this way and that explains it. Thanks for sharing.
I figure in a car it'll ask depend on the pressure on the system.
No, they don’t. Below 20ish degrees they are worthless.
It doesn’t get bitter BITTER cold here but sometimes it does and half the city
without gas freezes.
It depends on whether it's a ground source or air source heat pump and what unit you buy. There are definitely both ground and air source units that do well below 20 degrees these days as the US has in recent years started importing Japanese multi-stage air source heat pumps. However, it's not a blanket all temperatures below 20 degrees. The best air source heat pumps can maintain a COP above 1 into the -10Fs to -20Fs, but after that you might as well use a combustion or resistance heater with a COP of close to 1. A friend's parents in Maine had a two-stage ductless mini-split air source heat pump system installed into their home a few years back and it's apparently saved them boatloads of money though they still have a fireplace they light up because they like it. Within the US, Maine's taken up heat pumps to a pretty high rate in recent years with the introduction of these units, but large parts of Scandinavia, South Korea, and Japan (including some pretty cold parts of Japan) have been using them for far longer though some of that is ground source heat pumps.
As real world demonstrations of existing mass production EVs with heat pumps are show, and there's a lot of videos and articles out there, that bottom temperature range works fine for EV heat pumps as well. It's somewhat different for EVs, because they are sometimes designed in clever ways that also move heat from other sources within the unit like the drive unit so it's not purely an air source heat pump though not all EVs with heat pumps have that level of integration. You can see a lot of real world tests of these EV heat pumps being used in Canada and Scandinavian countries which generally probably see harsher winters than what the vast majority of the US population lives. Of course, those Canadian tests aren't way up in the Yukon, Northwest Territories, or Nunavut, but more within a couple hundred miles of the contiguous US border. Even with better integration, it's probably going to be a while before heat pumps approach their theoretical efficiency limit where they're useful in a harsh Fairbanks, AK winter.
Of course, the multi-stage air source heat pumps are more complex and more expensive than the single stage air source heat pumps that have been the main heat pumps sold in the US and generally were sold in warmer parts of the US.
Last edited by OyCrumbler; 04-26-2022 at 04:12 PM..
If that is the case your home probably needs better insulation and less air infiltration.
Even doing that won't make a difference with heat pumps. Newer ones are better than they used to be but bitter cold weather (meaning below freezing) causes them to become inefficient and triggers the resistance heat to operate.
Even doing that won't make a difference with heat pumps. Newer ones are better than they used to be but bitter cold weather (meaning below freezing) causes them to become inefficient and triggers the resistance heat to operate.
Even doing that won't make a difference with heat pumps. Newer ones are better than they used to be but bitter cold weather (meaning below freezing) causes them to become inefficient and triggers the resistance heat to operate.
Freezing is at about 32F and the temperature spectrum goes all the way down to −459.67 °F. There certainly is a large range that's below freezing where modern day air source heat pumps won't work well, but few people live in places that get substantially below what modern day air source heat pumps intended for cold weather use can handle. Your link is to the air source heat pumps they install which are fine for fairly warm winters. However, that probably differs from what gets installed in cold climates like northern Japan, northeastern US, Scandinavia, or elsewhere that can get somewhat cold winters. In those areas, for air-source heat pumps*, they generally install heavier duty units like this:
That one, which is one of many from Fujitsu, Daikin, Mitsubishi, or Trane (the odd one out on this list) that are rated specifically for use in cold temperature and that one says it's good to -14F which is substantially below freezing in terms of climates that people live in. Keep in mind, the actual temperature at which these will provide heating is well below the rated -14F--it's just that they get less efficient at getting to a temperature a person would normally want when the temperature differential gets larger and so at a certain point you might as well use a resistance heater or something else. These aren't that great for places that get prolonged and extreme winters though like Fairbanks, AK which gets to -40F pretty often and can go down to -60F.
EVs can do one better than in use given its small space and that there are other sources of heat that a heat pump, if cleverly designed, can wick heat from aside from the air. There's also generally some resistance heaters often built into the EV (and many cars in general) including ones that are very close to the occupants like in the steering wheel or the seats.
*homes can also use ground source heat pumps or similar rather than the outside ambient air as the ground has much higher specific heat on average so a lot more heat can be drawn from the ground. Ground source can even work well in arctic climates
If that is the case your home probably needs better insulation and less air infiltration.
Actually both of my units are natural gas.
Now are people denying things that don't work in houses, either?
About 5 years ago it got to 10 degrees and below. I had to go sleep at parents' house where there was gas and half the city was shut down early the next morning bc heat pumps don't work very well if at all when it's that cold. Like I said, it gets cold here but rarely frigidddd cold, so about half the city has gas and the other heat pumps.
I'm not knocking Teslas, I'm just saying that a "heat pump" doesn't work when it's bitter, bitter cold outside for a home at least.
According to the person explaining how the Tesla Y's heat pump works, the point of no return is perhaps 0-degree F.
In this case the pump doesn't move heat to the cabin. Keep in mind that the pump needs battery power to work, but if the ambient temperature (outdoors) is not "too" cold , the heat pump could still be more energy efficient than resistive heat alone (at least the way I understood by watching the video):
All heat pumps do for EV's is to reduce the amount of energy needed to heat the cabin versus resistive heat alone, but as the ambient temperature (outdoors) gets colder and colder and reaches zero (0) F., the pump is not longer any more efficient than the heaters. It seems that these pumps are great for EV's in places with moderate climates like OyCrumbler has said above.
Heat pumps for home use work well too, but all depends on how cold it is inside the house versus outside. For example, in cold climate the ground below (sub grade) could be warmer than the surface. In this case, the heat pump can extract some heat from the ground during the winter months. But if the ground has "permafrost," then there aren't any benefits of using heat pumps to heat the home. Where I live at the ground can be completely frozen 3' to 4' deep, but it's above freezing deeper than 4-feet of so depending on permafrost and things like that. The lakes' water surfaces freeze from 3' to perhaps 4', but down below the water doesn't.
Now are people denying things that don't work in houses, either?
About 5 years ago it got to 10 degrees and below. I had to go sleep at parents' house where there was gas and half the city was shut down early the next morning bc heat pumps don't work very well if at all when it's that cold. Like I said, it gets cold here but rarely frigidddd cold, so about half the city has gas and the other heat pumps.
I'm not knocking Teslas, I'm just saying that a "heat pump" doesn't work when it's bitter, bitter cold outside for a home at least.
The Tesla heat pumps have 15 different modes (3 AC and 12 heat) - they use fairly novel ways to generate heat to feed the heat pump if it is bitterly cold - the main one is using the compressor to generate waste heat to circulate back to the cabin. Commercial buildings with heat pumps sometimes use similar tricks if too cold but few home units can use this method. -
BTW - all Tesla's now use heat pumps - for almost all use a heat pump is much more efficient - where it is very cold, the heat pump is just as efficient as resistive heat source.
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