That happened in NorCal in 2019. There were no generators to be had south of Chico, CA that summer. Had to go halfway to Redding to a random Home Depot that didn't have a large customer base. When you need a generator because PG&E decided to have a PSPS for a week or 2 without warning, then you need it immediately. It's not a panic purchase when it's an emergency purchase of inelastic necessity, not hoarding of 4000 rolls of toilet paper.

Most residential solar sets in California lack battery backup capacity and do not generate power in the absence of grid power "for safety". This is because most homeowners are uninformed consumers and don't know what options they need.

The trick with a gas generator is to have an electrician install an interlock on your electric panel along with a hookup to your generator. Then it's a snap to switch over to the generator, and start it.

The only trouble is that gives no indication when the power comes back on. So there you are, generator blasting away, while power is restored. Leave a couple circuits always connected to the line power, and hook those to a radio or a light so you know when the line is back up.

P.S. if you get a generator with an electric starter, odds are good the battery will be dead. The trick is to add a couple power posts to it, so you can jump start it with your car.

I use a mechanical interlock like you have described and I actually prefer it to a more complex ATS. I like simple systems.

But you can, in fact, see when utility power comes back on if you have a "smart meter" - the LCD panel readout is dead/blank during the outage but is active and displaying once the power comes back on.

So we just peek at the meter every once in a while to see if PG&E is back ...