I've had the surface for about a week now. I5, 8gb, 256gb. And have been writing down every 30-60min what time and what % of battery life to keep track. I have balanced power profile, brightness 35%, wifi on, Bluetooth on, and any program specific settings if allowed to max battery. What I found and see is that I get between 4 and 4 1/2 hours. That's web browsing single tab at one. IE in metro or desktop. 4.5 hours Web browsing multiple tabs, again metro/desktop doesn't matter. 4-4.5 hours ITunes playing local music and word processing. 4-4.5 hours. One note while inking right half screen, kindle desktop left half screen. 4 hours My normal day would consist of one note, kindle desktop (ebook), slacker/iTunes (local), email, and web browsing. Also 4 hours. Also, for one note. I started with my notebooks syncing to One Drive. Have tried moving them to local storage to leave wifi off, 4.5 hours with wifi off, 4 hours wifi on. Anything battery wise I can do is best. Live tiles off, no syncing, push to for anything, any setting I can find is for battery, IE tracking protection, using windows defender instead of avg, and no malware bytes, and screen at 35% (which sometimes is less than ideal). And I still haven't reached 5 hours even. I don't understand how all these 'professional' reviews got 8 hours web browsing. Only using one app/program at a time. Only programs I have installed are office 365, iTunes, kindle for desktop, HW info, and stardock. All windows updates are installed and up to date. Also mention this is my second surface pro. First one had really flaky upon waking from sleep wifi, which led to crash upon waking from sleep. Battery life was exact between that and this one. Had that one for about a week, before returning.