Between El Nino and the undergrounding project(s), having a backup seems like a good idea.
First, I identified my essential loads: refrigerator, freezer, furnace, internet, phones.
Then, you measure... I used one of these
https://www.amazon.com/dp/B0D5QMK3BPGive it at least 24 hours on each load. It will tell you the minimum and maximum power draw, and the number of kilowatt-hours.
My load ranges from 60 watts to a bit over 1000 watts.
I have a power bank ("solar generator" is incorrect) with an expansion battery for a total of 6 kilowatt-hours. I've tested this, it's good for 24 hours. I have a dedicated outlet near each appliance that is not connected to SCE.
Testing shows that this is good for 20 to 22 hours, so if the power goes off in the middle of the night, we go back to sleep.
For longer outages (like the one last Christmas), I have a generator. Charging time should be less than 6 hours.
I don't have to drag out the generator in the middle of the night. I can wait until after my morning Coffee.
I don't have to run the generator when people are sleeping.
I don't have to tend the generator at 2:00 am.
Propane so I'm not storing gasoline. A 20 pound tank should keep things charged for about 3 days.
It's not quite as smooth as an automatic, whole house generator, but it's far less expensive.
Happy to share what I've learned if anyone is interested.