Chuch summed it up as good as it is. The only thing I can possible add is that when traveling there are 2 reasons to use DC and NEVER gas. 1st reason is the flame may blow out and allow you reefer to heat up possibly spoiling your food and more important reason #2 is... who want an open flame present at a gas station with all the gas being pumped into vehicles and gas fumes everywhere. Some state laws prohibit using propane to cool your reefer when traveling. Besides Im sure you dont have a death wish.