It’s possible to get larger propane tanks and refill them more cheaply (rather than exchanging expensive grill tanks at the store). Some hardware stores will refill tanks directly. You can even get very large tanks (refilled by a truck that comes to your house) if you want weeks of power on tap. But this is probably overkill for most, unless you’re very remote.
This is a common enough occurrence in rural Louisiana, at least. And I think almost everyone I know has a 200gal or larger propane tank in their yard, specifically for multiday outages. My father-in-law doesn't have a single propane appliance, but he does have a 250gal tank, for his generac.
We don't we have a single 100lb tank, but that will run the little AC for 3 or 4 days.
This is important enough to me that I researched slow start AC units ~8 years ago when replacing my AC. I learned that almost any heat pump will do, so that's what I have.
https://hsph.harvard.edu/news/heat-waves-and-annual-death-ra...
In a traditional house with thick brick/stone walls and large roof overhangs you'd be uncomfortable but a lot less likely to die