AnandTech 

"When Steve Jobs announced that the MacBook Air would have a 5 hour battery life, I laughed. Short of Apple sticking a hydrogen fuel cell in the Air there was simply no way you were going to get 5 hours out of this thing under any sort of heavy usage. What shocked me even more is how few questioned the 5 hour figure. Have we all forgotten about optimistic battery life ratings? I like to give Apple the benefit of the doubt and not call out RDF whenever a new product with exciting features launches but seriously folks - 5 hours?

We're still hard at work on the MacBook Air review, but this data was too important not to share right away. By now you've heard that under "normal" usage, the Air can only manage about 2.5 hours of battery life. That's true and at the same time it isn't. I touch on part of this in the review, but the MacBook Air isn't designed to be your work notebook - no ultra portable is. It's a notebook for a writer, for someone taking notes in class; it's a second notebook, or a third system. As such, the typical usage model can be very different than your standard notebook.

At the same time, most of the people considering the Air aren't looking at it as a second notebook or a third system, they are looking at it as their primary notebook (and will be left sorely disappointed or frustrated after a while). The end result is that you need a handful of battery life tests to really cover all bases. And that's what I've done."

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