Microsoft Surface: Battery Life Analysis
Last week we published our first impressions of and experiences with Microsoft's new Surface tablet in Microsoft Surface Review, Part 1: Performance And Display Quality. In that piece, we covered the platform's underlying (familiar) Tegra 3 SoC, a handful of browser-based benchmarks, and an analysis of display performance at maximum brightness.
With one more week of tinkering under our belts, we're ready to follow-up with even more data you can use as you decide whether the Surface is the tablet/notebook go-between it's being made out to be. We have a comprehensive look at battery life with the tablet at maximum brightness, and then normalized to 200 nits, a second analysis of Windows RT, a demonstration of external monitor support, initial experiences gaming on the Surface, and additional discussion of display quality.
Let's just right into our exploration of battery life!
Battery Life & Recharge Benchmarks (Background Info)
The Surface does surprisingly well in our first test, which looks at battery life during the playback of an H.264-encoded movie at 50% volume. Microsoft's tablet lasts for more than seven hours, besting a number of notable tablets, but trailing behind some of today's most popular models like the third-gen iPad and Nexus 7.
As some of you have noticed in past tablet reviews, our Web browsing benchmark is more taxing than the video playback workload. This is because most SoCs are able to offload the most intensive aspects of the decode pipeline. Moreover, we disable Wi-Fi in that test. Meanwhile, the browsing metric scripts a text-heavy site to reload every six minutes. Wi-Fi is active, and it doesn't help to have MP3 playback going at the same time.
As a result the Surface touches six hours of battery life in our second suite, topping a number of the tablets it previously lost to.
Here's the thing, though: we ran those figures with each tablet's display set to maximum brightness. Some folks are going to use their devices like this, making it an interesting comparison. However, it's not a scientific-enough measurement to stand alone because each tablet's screen is different, resulting in different maximum brightness levels.
So, we take the extra time to go back and run the same tests with each tablet fixed to the same luminance level. This is problematic in its own right, since we'd be inclined to dial up the brightness on a low-gamut display. At least both schools of thought are represented though, right?
Normalized Brightness Benchmarks
Standardized to 200 cd/m2 (or nits), the Surface lasts for 10 hours playing back H.264-encoded video content. Although that's an hour less than the Nexus 7, the delta between both devices is narrower here than it was at maximum brightness.
When we switch over to Web browsing and music playback, the Surface runs for two hours longer than it did at maximum brightness. However, it still trails the Nexus 7, third-gen iPad, and Kindle Fire HD.
Powerful graphics architectures make lightweight gaming a reality on today's tablets and smartphones. Unfortunately, it's difficult to pin down cross-platform tests because there are so few games that run on iOS, Android, and Windows RT. Riptide GP is a rare exception, which makes it possible for us to use the game to test battery life. Our measurement is pretty simple: we play back the demo loop until each device shuts down.
We've found this game to be unforgiving of Tegra 3-based tablets because it's specifically optimized for Nvidia's SoC, taxing it with additional quality enhancements. If you game on the Transformer Prime or Nexus 7, you'll see additional details like water splashes that don't show up on other tablets. Interestingly, though, the Surface outperforms the other Tegra 3-based models, even exceeding the third-gen iPad's battery life, all the while giving you better visuals.
As the Surface delivers comparable battery life as Apple's third-gen iPad, it also impresses by enabling much speedier recharging times.
For every minute you spend browsing the Web and playing music on the iPad, you need to spend the same amount of time charging it back up. Six hours of battery life, six hours of charging.
Meanwhile, the Surface cuts that time in half. You can browse the Web at full brightness for six hours, and then spend three hours to charge back up to 100% capacity again. We're only missing one piece of this power puzzle: what impact does charging more quickly have on the Surface's battery's longevity?