we have an Igloo thermoelectric cooler (one of the almost mini-fridge size) and my sister had one that was a Coleman. Hers just quit running one day. Ours has worked fine for three years. We use it for long trips. It keeps milk, yogurt, cheese, etc.etc as cold as a fridge. You must remember to pre-cool it though (leave it plugged in for about 4 hrs to cool down before putting stuff in it). It is rather noisy, but it's a "white" noise that is OK in a hotel room.
we can't leave ours plugged in w/the engine off -- it will not keep running. That's a function of our SUV, though -- when the key is not in the ignition, it will not charge cell phones, etc etc