What is the battery life of the "Mid-2009" and "NVIDIA/Late 2008" MacBook Air in real-world usage tests?

Please note that the "NVIDIA/Late 2008" MacBook Air was replaced by the "Mid-2009" MacBook Air on June 8, 2009.

For the original MacBook Air, Apple stated that the notebook could provide five hours of battery life with wireless activated. Critics flambéed this claim, finding battery life to be significantly inferior in real-world use.

For the NVIDIA/Late 2008 MacBook Air -- it is interesting to note that despite the fact that the energy consumption of these models is less than the original -- Apple only estimated 4.5 hours of battery life in a "wireless productivity" test, perhaps a quiet admission that the number reported for the original system was a bit more optimistic than it should have been.

Nevertheless, those who follow the computer industry are used to practically irrational optimism from companies reporting battery life, and as a result, only real-world usage tests can provide a realistic estimate.

In an otherwise comprehensive review of the "NVIDIA/Late 2008" MacBook Air, MacWorld did not test battery life, but IDG sister publication ComputerWorld did, and reported:

According to Apple's [Director of notebook marketing Todd] Benjamin, all of Apple's laptops now range between 4.5 and 5 hours of battery life. If you're playing videos or watching a movie, Apple says you can expect between 2 and 2.5 hours of use. And since the battery is integrated, there's no swapping.

[For the NVIDIA/Late 2008 MacBook Air], I had the brightness at maximum for about an hour, turning it down gradually as the light in the room changed. I managed 3 hours and 49 minutes, and could easily have squeezed out more time by dimming the screen more aggressively.

In its own testing, SlashGear found the officially estimated numbers to be realistic:

Apple quotes 4.5 hours from the new Air, down thirty minutes from the original, and while we never like to see usage times moving in that direction we at least found that to be an accurate estimate. With the backlight set at half (which, thanks to the LED system, is no hardship) and Wi-Fi turned on, we managed around 4.25 hours of casual surfing and emailing. Watching video halved that, and video processing is an even quicker way to drain the battery.

In a short mini-review, Engadget felt that the battery life was reasonable but still wanted either more runtime or a swappable battery:

We'd say the average battery life with mild use -- about three hours, very much on par with the previous version -- is plenty acceptable, but for a laptop that so encourages portability, the inability to replace the battery means you can never be more than three hours away from an outlet, less if you want cellular internet.

For the "Mid-2009" MacBook Air models, Apple officially bumped the battery life back up to 5 hours with a new 40 W/Hr battery (up from 4.5 hours of battery life and a 37 W/Hr battery in the replaced "NVIDIA/Late 2008" model).

As the "Mid-2009" MacBook Air models were not substantially different than the models they replaced, they did not attract a lot of detailed attention across the blogosphere, but MacWorld tested the batteries by playing a movie on continuous loop ripped from DVD and stored on the hard drive. Movies were played in full screen mode with full display brightness, but keyboard illumination turned down and wi-fi turned off.

Playing a movie on continuous loop is considerably more demanding on the battery than the rather light "wireless productivity" test that Apple performs -- although turning wi-fi off does conserve battery life -- and MacWorld found the "Mid-2009" models -- the MacBook Air "Core 2 Duo" 1.86 13" (Mid-2009) and "Core 2 Duo" 2.13 13" (Mid-2009) -- to provide 2 hours and 49 minutes and 2 hours and 37 minutes of runtime, respectively. By comparison, this is 20 minutes and 16 minutes longer than the replaced "NVIDIA/Late 2008" models -- the MacBook Air "Core 2 Duo" 1.6 13" (NVIDIA/Late 2008) and "Core 2 Duo" 1.86 13" (NVIDIA/Late 2008) -- in line with Apple's estimate.

Ultimately, it appears that the numbers quoted for the "Mid-2009" and "NVIDIA/Late 2008" MacBook Air models are more realistic than those provided for the original model. However, as Apple notes as well, battery life may vary depending on "configuration and use" and this is clearly reflected in the real-world tests performed.

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