[jhj]

I have some of (possibly the?) cheapest residential electric power in the US, at 5.58 cents per kWh all-in cost here in Wyoming, 90%+ hydropower.

Absolute lowest cold here each year will be around -30 F / -34 C (there will be several nights in the winter where it gets below -20 F / -29 C), and absolute hottest it will ever be around 85 F / 29 C, but average annual temperature is about 35 F / 2 C. It can snow any month of the year here, with snow on the ground usually between November and mid May.

My house was built in 1968 and I have primarily resistive baseboard heating, with a large Mitsubishi mini-split installed by my home's previous owner mainly for air conditioning purposes in major rooms for a couple of weeks in the summer. I live at 6500 ft / 2000 m altitude, so even on the hottest summer days once the sun goes down it gets quite chilly and can get close to freezing, so it's really just for a few hours in the afternoon for a/c purposes. I otherwise use the heat pumps as baseline heat in the winter.

I'd like to put trust in heat pumps more because they are obviously more efficient (also as seen by my already low power bill), but lack of heat on certain days in the winter has serious implications here for home integrity, and while this might just be this one Mitsubishi model (though they are less than 5 years old), I haven't been left with a good opinion of heat pump design and repairability in general and am not tempted much to explore heat pumps further.

The heat pumps are rated to work down to -5 F / -21 C in the manual, but in practicality it's more like 15 F / -9 C otherwise they just spend a large part of their time defrosting. The models I have don't seem well engineered for reliability or maintenance either, there are important fuses hard-soldered to the main board that are not individually replaceable, and true enough in the middle of winter my HVAC technician and I had to bypass the blown fuses with an automotive fuse we had (same stats) attached with alligator clips, as it would take weeks or months to obtain a new $1500 (!) main circuit board from who knows where. On the other hand, resistive heating usually just works assuming you have power, and I also have two fireplaces as emergency backup if there's no power (though power lines are almost all buried here due to snow/ice anyways).

I really would like to see more emphasis on reliability and repairability rather than, like, SEER, HSPF, or COP ratings or whatever.

[throw0101d]

See perhaps the "Cold Climate Air Source Heat Pump (ccASHP) Product List and Specifications" from the Northeast Energy Efficiency Partnerships (NEEP):

* https://neep.org/heating-electrification/ccashp-specificatio...

And their product list:

* https://ashp.neep.org/

One of the search criteria is their rated capacity (BTH/h) at 5˚F. A 'proper' installer will figure out the energy you need for the design day in your area:

* https://www.greenbuildingadvisor.com/article/design-temperat...

If you're in a really cold area (IECC Zone 7+), then a dual fuel system could be one option:

* https://www.carrier.com/residential/en/ca/homeowner-resource...

* https://www.lennox.com/residential/buyers-guide/guide-to-hva...

* https://www.trane.com/residential/en/resources/glossary/dual...

Of course before you go spending money on equipment, it's probably a better ROI on better air sealing / draft elimination and insulating. Once you're not leaking (as much) heat then you may need less powerful equipment to keep indoor conditions comfortable.

[masterj]

Our heat pump (~2 years old) doesn't seem to have much trouble with -21C, though we rarely get down that low. With frequent temperatures that cold, a combo unit with natural gas backup for the coldest temperatures likely makes a lot of sense.