Microsoft claims that its Surface 3 will last for up to 10 hours. Of course, battery life will depend on how much you require of the system throughout the day, and quoted times have historically been "best case scenario" results. That said, we did feel comfortable that the average user could get 10 hours here, mostly because you probably won't be gaming or cranking through any seriously taxing work. With moderate loads that run smoothly on the Surface 3, you could probably keep the slate on for the entire duration of a flight from Atlanta to Honolulu. (Mmm, Hawaii!)
In an attempt to quantitatively measure the battery life in a controlled benchmark environment, we ran two tests to get a sense of how long the system will last under light and heavy use. Our web browsing test is a light-use scenario in which it refreshes a webpage over a Wi-Fi connection until the battery is exhausted. For this test, we set the display to 50% brightness and connected to the web via a wireless network.
The Battery Eater Pro test gives the machine a much heavier workload to simulate the kind of stress you might put on the sytem with multiple resources engaged including CPU, GPU, memory and hard drive.
The Surface 3 held up well under both battery tests, finding itself in the top class. As far as svelt 2-in-1 units go, this one's pretty good in terms of battery life. It doesn't offer the same untethered battery life as some devices with larger batteries, but over 8 hours of non-stop browsing is not bad at all.