Auto invert means that anytime the coach loses power the inverter will kick in an power those 120V outlets to which it is attached. If you do not want the inverter to kick in an drain your batteries then you would flip it the other way. In that setting, your batteries will still be charged when on shore power but if you lose, or disconnect from, your 120V shore power connection you will have no 120V power available in the coach but you will also have no (minimal) drain on your house batteries. When I am in my coach I always have the inverter set to automatic. If I was storing a coach without power you do not want the inverter to kick in so the switch goes the other way.