Seriously, the large water tanks are excellent. When electricity goes off around here, which it has sometimes for a week esp in the winter with snow storms, we always have water when no one else does. Everyone around here has wells except in the “city” (1000 residents I think) a few miles down the road. No power means no pressure tank either but we have two faucets that are gravity fed.
Also since there are a lot of wildfires around here, DH has a set up to access water tanks so he can fight any fire on our property.
When he bought the tanks they were about $1 per gallon capacity, who knows what they are now, or in your area. We do not use for drinking or cooking even though they are graded for potable water; he has a 900 gallon stainless steel tank (used to be a milk tank) he pump the well separately for drinking and cooking, and a gravity faucet for that one.
A lot of the farmers around here use something similar for watering livestock that are too far from running water or creeks. They are poly tanks in a cage that they haul on a trailer or the bed of a ton truck. I think they are about 500 gallons. My SIL is talking about buying one for his new garage.
I have options to check out now. I’ll check out the portable tanks, the Generac, and a few others.
If I notice that we are going to have high winds or a storm, I have been filling the bathtub with cold water to flush the toilet. All it takes here is a high wind and we have trees all over the powerlines.