I leave my fridge on auto all the time. Cooling power is basically the same for either gas or AC power, so if AC power is available I'd prefer not to use propane that eventually needs to be refilled. If your electricity (AC power) is coming from an inverter, you may very well want to use gas as the fridge uses a fair amount of electric energy over time, around 300W for maybe fifteen or twenty hours per day. Frequently an inverter would be installed so as to not power an absorption fridge, but there can be a lot of variation there.
AUTO mode does means use electric if available and gas if there is no electric power.
