Hi Pete, yeah -7F (-21C) here at the moment. I shut the heat pump off this afternoon. Some ice bridging up at bottom of coils from snow as we just had a storm. I will have to make a cover to prevent that next year.
When i was brooming snow off solar panels the sun was about half (over 5 amps on 8 amp panels) between the current and dark surface it melted and evaporated any remaining snow in an hour. I didnt look at OAT but it wasnt near melting anywhere else. So solar panels do clear themselves of snow especially if at correct winter angle.
Regarding open door to cool off house, HA! I have a buddy that does that often here even! Its a good problem to have😁.
It does warm here in summer, rarely over 100F(38C)usually hot is 90-95, my younger years we never worried about AC but now people see it as a requirement. Where i work is not air conditioned in the shop but offices are. Humidity here is quite high normally which counts for a lot.
I put together another graph comparing output of minisplits in heating mode and its real surprising how much variance there is. Cooling mode you are only working with a 20 degree differential so its not so much work but depending on where you live heating can require 70F (45C) of lift. The performance data is hard to obtain and for some reason doesnt match AHRI tests, very puzzling. But here it is. These are just 4 arbitrary units i looked at not necessarily the best or all inclusive of whats available. The top performer, 9Kbtu Fujitsu Halcyon XLT (hspf 14.2) next 12kbtuThermocore, (12) then a 9kbtu mrcool (12) and at the bottom, the pioneer (9.5) i have. The straight line is a 1350w resistive element which is supposed to represent consumption of each but only true of the pioneer maximum. Prices are $1800, $1100, 760, 750. The top 3 are all labled as "hyperheat" though the technology used is unlikely the same. I have not personally tested these so i cant speak for accuracy but most of the data came from mfr data sheets. Its also interesting the electricity used is not similar. For instance, the bottom one claims to be around 1250w full heat, i have verified. The Thermocore is using 2kw around the 0 degree mark. It goes down above and below that OAT. It kinda makes the graph misleading. So choosing one of these, price vs performance can be tricky as they are very dynamic animals but worth the trouble, like solar panels😁