You won't be able to use it for much of anything. Those kinds of 12V sockets in a car only run through about a 10 or 15A automotive fuse. So that's only 120 or 180 Watts. When you convert the voltage by 10X up to 120, that reduces the current by 10X, so you could only draw 1 or 1.5A of current. That's not going to be able to run very much other than small electronics stuff.