As Sitting Duck said ( I am a camper in tents ) and those electric cooler boxes do work pretty well except on the hottest of hot days. Basically they drop the temperature by about 15-20 degrees on their coolest setting. So for most days they are more than fine and hardly use anything. Obviously on days where the temp goes above 25 degrees or so then you can either flick the fridge on... or just drink your beer faster :D
