I plug in the trailer in a couple of days before I leave and get the fridge cold. I run it on battery while traveling. I freeze a couple of water bottles and include them in the fridge contents to help out while on the road, and if I need water in the car I grab one when I stop. Another fridge tip that works well for me: I purchased a few of those plastic mini-bins at the dollar store. I pack everything from the home fridge that I'm taking in those and then transfer them to the fridge. They also help keep things in place in the fridge while traveling. I use gas when I'm boondocking.