At 77F ambient temp, this thing is barely holding at 50F with 2 cans of beer and my reliable fridge thermometer inside. It's been running for almost 7 hours now and has been at 50F for most of that time. That is a -27F Peltier effect at 77F ambient, which is NOT what was advertised. I was lead to believe I'd get at least a 35F differential, so 42F is what I expected to see.
The simple truth is, the heat sink in this thing is undersized to save on weight and cost. WIth a larger heat sink, it could probably shed more heat and be actually useful as a fridge (35-40F). Above 40F is NOT reliable to keep perishable things cold.
If all you want do is make your sodas and beers cold, I guess this will work. Just know that everything you put in here probably has to be shelf stable stuff. Do not use it for milk, yogurt, cheese, or even fresh juice.
I haven't tested its capability in the car on 12V DC yet. If this is how it performs on AC, I expect low voltage DC current will be much worse.