I think this detailed FAQ link below may help you. Usually the inside switch is just for the propane side of the water heater on the Suburban's. The electric element switch is most times located on the face of the water heater itself, as explained in the link:
Suburban's electric switch and much more
FYI, this is one of the most ill-explained things from dealers during PDI's............. and thus one of the most frequently asked questions here.
You refrigerator can have an auto mode, that will sense whether it's powered by propane, 12 volt, or 120 volt.............but I can not remember ever seeing a Suburban water heater that could do this.