For that matter, as someone who lives in New England, if I wanted to install backup for extended power outages (which do happen where I am now and then), the sensible thing to do would be to get a propane-fueled generator installed because that would work if I were traveling (to keep pipes from freezing) and would also keep refrigerators running in a summer outage. (Added: Maybe a Powerwall-type thing would make sense today.)

I do have a fireplace and a wood stove which provide something of a backup but won't heat the whole house and only work if I'm there.