A lot of the pop ups have the three way fridges that can run 12v (although I do agree with the statement that MOST rv's only have 120v or propane). I only used the 12v when towing as the tow vehicle can provide voltage to replenish what is used. When running 12v for the fridge uses a lot of amps to work so if I was going to be parked greater than an hour I would switch to propane until we got running again. Have had it happen (very first time with a rental) where I left the fridge on 12v and killed the battery before we even left. Spent most the weekend recharging the battery with jumper cables off the TV.
2014 Stealth Evo 2850- "Woodstock"
2011 Toyota Tundra Rock Crawler TRD 5.7- "Clifford"
2013 Honda Accord Coupe V6 w/Track Pack- "Julia"
Just glad to get away