Our camper came equipped with the Norcold N10DCX - 10 cubic foot unit. I've got a 200 watt solar panel and a single deep cycle 12v battery. The other day, while installing a hardwired EMS the refrigerator was on battery (along with the lights) for about six hours. It was a cloudy day and the refrigerator started beeping (indicating low power) after about five hours.
When I purchased the camper, the refrigerator was turned on to maximum cooling on both the upper and lower sections. I drove from Michigan to West Virginia with no battery at all (dealer failed to install one), yet the refrigerator was happy to run on the voltage provided by the truck and/or solar panel. Since most of the drive was made in the rain, I imagine the unit was being powered primarily by the truck and would have run indefinitely while going down the road.