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What is the battery life of the "Mid-2011" MacBook Air models in "real-world" usage tests? Do the faster custom-configured Core i7 models have inferior battery life than the standard models?
Please note that the "Mid-2011" MacBook Air models have been discontinued. However, this Q&A is up-to-date and is particularly useful for anyone considering one of these MacBook Air systems on the used market. These MacBook Air models can be identified externally by the 2469 and 2471 EMC numbers.
Apple formally estimates that the standard 11-Inch "Mid-2011" MacBook Air model -- the MacBook Air "Core i5" 1.6 11-Inch (Mid-2011) -- provides an estimated five hours of runtime with its integrated 35 watt-hour battery and the standard 13-Inch "Mid-2011" MacBook Air model -- the MacBook Air "Core i5" 1.7 13-Inch (Mid-2011) -- provides an estimated seven hours of battery life with its integrated 50 watt-hour battery.
Photo Credit: Apple, Inc. (Left - 11" MacBook Air, Right - 13" MacBook Air)
Official Battery Life Testing Criteria
In fine print, Apple explains that this battery estimate is using stock configurations performing a "wireless web" test. The company further explains that the "wireless web test measures battery life by wirelessly browsing 25 popular websites with display brightness set to 50%." and also disclaims that "battery life varies by use and configuration."
Both the 11-Inch and the 13-Inch model can be custom configured with a faster 1.8 GHz Core i7 (I7-2677M) processor at the time of purchase, and Apple does not formally report the battery life of these options. For convenience, EveryMac.com also crosslists these CTO configurations as their own models.
In recent years, Apple's official battery life estimates have been reasonable, but test results from independent third-parties nevertheless can be worthwhile.
Third-Party Battery Life Test Results
In addition to the possibility of greater objectivity, independent testing methods can provide a more well rounded view with a variety of usage scenarios for the officially reported standard configurations as well as the unreported custom ones.
In a simple battery rundown test that is much "harsher" than the official one, Engadget hit the stock 13-Inch model with a video loop and discovered that the battery would last for five hours and 32 minutes booting Mac OS X Lion and four hours and twelve minutes booting Windows 7. Based on this testing, the blog concluded:
In standard usage, surfing and typing and Facebooking and such, you should be able to do much better. The Air routinely beat our expectations -- and its own estimates -- for battery life.
In another video playback test -- specifically playing a movie file "in full-screen mode at full brightness, connected to a Wi-Fi network, with the backlit keyboard dimmed, and volume on 2" -- MacWorld tested both the 11-Inch and 13-Inch models and reported:
Roughly three-and-a-half hours for the 11-inch model and five-and-a-half hours for the 13-inch. Those figures were both improvements on the battery life of the previous-model Airs. (The increased speed of the build-to-order Core i7 processor option didn't have a major impact on battery life, either.)
All three tests should be reviewed in their entirety, but for the heavy multitasking test -- which has "three open Safari windows, each browsing a set of web pages with between 1-4 Flash ads per page, at the same time. . . [while] playing an XviD video in a window all while downloading files from a server at 500KB/s," the site opined that the "new Airs do relatively well under heavy load" but:
Looking at absolute numbers however the data is less impressive. The 13 is borderline acceptable with its 3.75 hours of battery life, while the 11 is a bit more disappointing at under 3.
There's basically no impact on battery life from the i7 upgrade. Note that none of these workloads keep the CPU pegged at 100% throughout the test. . . If you're going to be doing a long 3D render or compiling a very large project (multiple hours) you can expect worse battery life from the i7. Typical notebook usage models however shouldn't see much of a difference at all.
Battery Life Summary
Ultimately, Apple's official battery life estimates for the "Mid-2011" MacBook Air models are reasonable -- five hours for the 11-Inch models and seven hours for the 13-Inch models -- regardless of processor for basic productivity use and surfing the web without Flash use. As always, however, real-world numbers may vary depending on the tasks performed as is demonstrated by the variety of independent tests above.