> Would a generator be able to supplant the grid?
Yes.
Our neighbor across the street depends on a respirator. We live in a rural Bay area location that has grid dropouts several times a year. Some last a few seconds, some more than a day.
His setup: A transfer switch operates ~ 3 seconds after grid failure, followed ~ 2 seconds later by autostart of a propane generator. His house stays on generator power until the grid comes back up for at least 5 continuous minutes. Then the transfer switch flips back to the grid and the generator shuts off.
Why propane? Because gasoline slowly degrades (polymerization) and needs to be drained, disposed of, and replaced with new (typically every year or so). Propane doesn't degrade over time.