I've got a 20kw Onan standby generator that I bought for the reptile business years ago. Auto starts when the power goes out. At least it used to. Now it just tries to start up, and either dies, or pops the breaker in the control box and then dies within seconds. I can't see anything obviously wrong, so trying to get someone to come out here to check it out.
Came in handy during hurricane Michael as it kept the power going for the four days it was out. Connie and I had evacuated, so at least we didn't have to worry about getting back in time in order to put power to the chest freezer in the old reptile building to keep everything from thawing out and going bad.
It's a handy thing to have around, so hopefully it won't cost me too much to get it fixed. Unfortunately it doesn't run the house, only the old reptile building and mouse building. Oh yeah, I have the garage tied into that circuit too. But the freezer gets power as does our water pump. And in a pinch we can set up cots in the reptile building if needed.
BTW, if you do get any sort of UPS system, make sure you get a true sine wave output or you could wind up burning out anything you use it on. Some electronics and even motor windings don't react well to a modified square wave power source.