From a techie point of view, electric cool boxes are only 11% efficient at most and draw about 3-4 Amps off a 12 V supply. Also the amount of 'cool' you get is dependant on the outside temperature and the efficiency of the insulation, as they can only shift a certain amount of the heat before reaching saturation. A cheaper solution is a thick walled polystyrene box. with a close fitting lid (which is very easy to make.) As others have said put in the deep frozen milk and other bulky liquids and pack the sausages etc around them. Most out of the way places in Europe still sell ice for those villagers without a regular supply of electricity.
------------- "It's not about being handsome, it's about being passionate."
A day of all things motorhome and campervan. The show is held both in the main indoor arena and across the grounds. Catering, hot drinks and food options are available. Easy access to the site and free parking included. Win one of five pairs of day tickets