Well, Apple says so (check the individual model pages, on the right). They say the 12" can get up to 5 hours (true in my personal experience) and that the 15" gets up to 4.5 hours. Anecdotal experience on this board seems to indicate that the 12" generally does better with battery life ... as one might expect. If you do a search on battery life and PowerBooks you'll find a wealth of information from users.carpet said:Do you get better battery life out of the 12 inch? If so, how much?