We found that even a well made Honda petrol genset was highly unstable feeding volts into a UPS for a machineroom. They are good at lights. They are good at a cooker. They suck at anything which expects regulated, non-noisy volts.

Lots of homebrew 'you can plug this magick cable I made' methods to supply volts across the fence to neighbours houses when the power goes down are really bad: behind the meter is just as lethal as in front of the meter, if you get it wrong.

TL;DR if you need to read a website like this for clue how to avoid losing power, you are putting your life at risk if you don't follow code, and don't know what you're doing.