I haven't used the warming feature, but this worked well for cooling on my cross-country road trip.  The other reviewers that recommended plugging in to pre-cool it are definitely right!  My mistake was in not getting a wall adapter when I ordered the cooler.  One reviewer said it came with one, so I didn't worry about it.  However, now I see there are some questions about that and answers show it doesn't- just the car power cord.  The day before departure, I went all over town trying to find one. (WM, Target, K-Mart, Menards, Cabelas, truck stop)  I was happy to find one at a truck stop along the interstate.  Unfortunately, that didn't work and I didn't find out until I got to the hotel late that night.