The Surface Pro gets its juice from a 42Wh battery. With its hybrid form factor, it's safe to say that it's gunning for the same group of consumers as Ultrabooks. Thus, it's not unreasonable to expect similar battery life performance. Sadly, this is exactly the Surface Pro's Achilles' heel.
Using Powermark's balanced test suite that does an even split between Internet browsing, word processing, video, and gaming workloads, the Surface Pro's battery lasted only 2 hours and 42 minutes. That's easily two hours shorter than what the dock-less Samsung Smart PC Pro achieved. Even with the dock (that draws power for its two USB ports, keyboard, trackpad, and status LEDs), the Smart PC Pro still lasted longer than the cover-less Surface Pro. (According to our tests, neither the Touch nor Type Cover has any meaningful impact on battery life.) It's truly a catch-22 situation here: should you go for the Surface Pro with its better system performance, or the Smart PC Pro with its very much better battery life? If you're always on the move, with no easy access to a power point, the answer is clear. For another data point, the Surface Pro's battery life is very similar to that of the Sony Vaio Duo 11, but the latter we're comparing against runs a Core i7 CPU and has a slightly bigger screen.
Benchmarks aside, we also tried to use the Surface Pro as a desktop replacement to see how far into the day it can get us. Operating in Microsoft Office most of the time, with the occasional web and YouTube surfing, the most we got out of the Surface Pro was slightly under six hours. Understandably, the more time we spent watching videos and playing games, the faster we had to reach for the power adapter.
The HWZ Portability Index factors in battery life, weight, and volume so you can decide if it’s worth your while to carry a mobile product around compared to the competition. As you can see from the table below, the Surface Pro scores well for this thanks to its low volume and weight. The Ativ Smart PC Pro is the runaway winner due to its superior battery performance. With the keyboard dock though, the Smart PC Pro actually scores lower than the Surface Pro with either the Touch and Type Cover, and that's because the dock now renders the contraption much thicker and heavier. On hindsight, Microsoft is spot-on with the design direction of its keyboard covers, because the combination of a poor battery life and a bulky keyboard is pure suicide for mobile usage.
On a side note, the sliding form-factor Ultrabooks like the MSI Slidebok S20 and the Sony Vaio Duo 11 both have a portability index that sits in between the Surface Pro and the most typical Ultrabooks. Given their versatility, it's good too see them fare just as they are intended and are great options for those who need one complete device that can handle a variety of situations. They will also likely appeal to those who can't make up their mind as to what form factor is a safe option.