Here's a scenario - it's not yet -10 celcius so the heat pump will try to scavenge outside heat to achieve COP of >1. Problem is that the rad is fully blocked with snow so whether the temp is -1 or -31, your COP is now = 1 because the heat pump is in "Stalled" mode, "mode 9", "compressor heating" or whatever you want to call it when input power (~7 KW) is all that's heating the cabin and battery. I am imagining that it's not that far of a stretch for the car to detect that if outside temp is higher than minimum operating temp for the Freon to be able to scavenge heat out of (I believe that is around -10 Celsius) and the current heat output is at or close to COP=1 then close louvers, heat the rad to melt the buildup, try again in a few mins to open louvers to get COP higher than 1. I'm imagining that such cycling would allow the intermittent COP>1 to more than compensate for whatever power loss was required to melt the ice on the radiator.
Here's a picture of our Model Y from 15 minutes ago after we parked in the garage. It was -2 Celsius outside and snowing on the way back. Arrows are pointing to the snow caked onto the radiator and as you can see the entire surface area is fully blocked by the snow. I'd really love to know when the louvers actually operate outside car wash mode. Clearly they're not doing anything here. Finally, heat pumps should have a defrost cycle, I'm suspecting that it does not turn on defrost mode often enough for real-world driving. Again, I'm sure all this can be determined by comparing the expected COP of the heat pump versus the outside air temperature then closing louvers and defrosting the radiator. Future software update for further "cold weather improvements"? If you want to get real crazy you can run the fan to check how blocked the rad is - no restriction means less RPM for the fan, blockage allows the fan to spin at higher RPM. All software stuffs that can be be put into curves that can be read and compared to sensor readings to avoid issues and gain maximum COP for actual real-world conditions. (Yes, winter driving in Canada is a real hell.)
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