How about keeping an ICE-powered generator for those several days in a year when the sky is stubbornly cloudy and dark? Could make sense for remote houses.
BTW keeping your house connected to the mains costs $10-20 / mo, even if you consume nothing. Connection cost is one-time, but likely several thousand.
Or an EV. I only need enough instant battery capacity to last a couple hours. That would handle the vast majority of outages I ever experience, all by itself. If it looks like it is going to be longer, I grab the cable from the transfer switch and plug it into my Lightning. That would get me through a hypothetical week long outage.
BTW keeping your house connected to the mains costs $10-20 / mo, even if you consume nothing. Connection cost is one-time, but likely several thousand.