RV refrigerators don’t work the same way your home unit does. Your RV unit uses heat to create a chemical reaction which, through evaporation and then condensation, cools the cold box.
The primary heat source for RV refrigerators is a small propane burner. Most units also include a 120 volt AC electric heating element for use when the RV is hooked up to campground shore power.
When you are not hooked up to shore power you will need to operate on propane. In camp, with shore power, it’s a matter of choice as to which you use; propane or 120 volt. You may prefer electricity simply because it increases the time between propane fill-ups. But a refrigerator uses very little propane compared to a water heater or furnace.
For more about RV refrigerators read
RV Refrigerator Basics and Is it okay to travel with my RV Refrigerator on propane? at RVbasics.com