The Surface with Windows RT lasted a decent but unspectacular 7 hours and 43 minutes in our battery test, which involves continuous Web surfing over Wi-Fi on 40 percent brightness. Sadly, Microsoft says that the upcoming Windows 8 Pro version will have half as much endurance. That would mean less than 4 hours of juice, which is unacceptable for a tablet.
Why does the Surface Pro have such a pitiful rated runtime? Part of the blame goes to the Core i5 processor under the hood, which simply guzzles more power than the ARM chip inside the RT version of this tablet. If I were Microsoft I would switch gears to an Atom CPU. This would allow users to still run desktop apps while offering longer battery life. Sure, you'll give up some horsepower, but the Surface isn't really designed to be your primary PC. Besides, an Atom-powered Surface Pro would also likely be cheaper. For example, Samsung charges $699 for its Atom-enabled Ativ Smart PC, and $899 with the keyboard dock. The Surface Pro will start at $899 without a keyboard.