On my setup, I have a automatic change over power relay that ensures all the 230 V sockets are always powered. The hookup cable inlet goes directly to the onboard charger breaker and the coil of a change over contactor coil. The inverter feeds the normally closed contacts and the outside power, the normally open ones. This then feeds the power panel that powers everything 230 V onboard. I use a 1500 W sine wave inverter that can run my inverter compressor air conditioner. With my 450 W solar panel, 375 A/h deep cycle AGM batteries I haven't felt the need to power the van from the hookup connection. My inverter is always online when my cabin power is on.