There are RV's with refrigerators that run only on 12v. We had a Coleman Tent trailer a long time ago, that had a "3 way" refrig....fortunately, the Heartland RV don't use them.
Problem with those is they will BURN through a battery in no time. I think we used battery only power once for a few hours when we ran out of propane and I had to drive to town to refill the propane tank.