Aportable generator is one option. Your 02 delivery company should leave you some big tanks for emergencies like a power outage. You can also call your power company and get on the list of people who need their power restored quickly. In a real bad situation, you can go to the hospital or the fire station; either has 02.

My oxygen provider left me with a cylinder that looks like your 'e' cylinders but is 4' tall and 10-12 " in diameter for outages. I'll have to check on the capacity. If it blew could probably ride it to the moon!!!

A "whole-home" outdoor generator was the Go-to for backup power during local or full-grid outages for many years. Fortunately things have evolved much with the advent of Solar Energy systems for common homes and EVs (cars). But even the newer solar systems can be very expensive to install.

Smaller, battery-based systems can be incorporated for less intensive uses like medical equipment only in the event of an outage. Take a look at this article and call a good electrician in your area to craft a solution for the few rooms in your house where you will need this coverage:
https://www.mediproducts.net/blog/topics/backup...
Be well.

I have a portable one that I keep charged however my mom had two portable tanks that she kept filled in the event of no electricity.