[rsync]

Remember: the best and easiest transfer switch is a physical interlock which costs $50 and doesn't wear out or fail, etc.:

https://www.geninterlock.com/product/generator-interlock-kit...

No certification required. Code compliant. Idiot-proof.

[jacquesm]

Seconded. You do need inverters that are able to work in island mode, which they definitely are not not all capable of doing.