I'd suggest the 12-volt version of the Hot Logic if you try this. According the best info I could find, it only uses about 45 watts. There's also no loss converting power to AC. I bought a 110 AC Hot Logic for use at home about 3-4 years ago, and have used it at least once a week on average ever since. I've been very happy with it so far, and the company that makes it as well. I also own the 12-volt version, but haven't got nearly as much experience with it. The few times I've used it, it's worked as well as the 110 version, and it seems equally well made.
If you do get a 12 volt mug, please be sure and review it here. I'd like to know more about them.