Sometimes a long laptop battery life is the key factor in why we own a laptop. CNET has done some extensive testing on which laptops have the longest battery life. Of course a netbook would be the winner in this category, but CNET has classified them into different classes. These classes are netbooks, 13-inch laptops, midsize laptops, and desktop replacements.

Each laptop manufacturer has their own determination on how long their laptop's battery life is supposed to last. So instead of having these results skewed, CNET did a benchmark by using a standard video playback test to see how long each laptop lasted playing a movie. Below were their results.

Source: http://news.cnet.com/8301-17938_105-20007267-1.html