In Wa. state it is a $50,000 fine to back feed the system. When you plug in a generator to the house you must have a certified generator transfer switch installed and inspected by the state.
We have a plug in box in our coach that allows the Newmar's gen/set to deliver A/C power to another unit. It is wired hot to the top of the automatic transfer switch. this allows us to share a camp ground post or our house 50 amp box, or to supply our house from our Newmar's generator.
every thing has been inspected and approved by the state.