MacBook Air Mountain Lion Battery Life: 10.7.4 vs 10.8 vs 10.8.1

Over the last several days we’ve been testing the battery life hit that many portable Mac users experienced after upgrading to OS X 10.8 Mountain Lion. We were interested in not only the initial drop in battery life caused by the upgrade to 10.8, but also in any improvement that users would see from Mountain Lion’s first point-update, 10.8.1, released Thursday.

We first recorded a dramatic 33 percent drop on our 2011 15-inch MacBook Pro (MBP) when upgrading from 10.7.4 to 10.8. The final build of 10.8.1 was a significant improvement over 10.8, but still left us far short of where battery life was on 10.7.4.

On the new MacBook Pro with Retina Display (rMBP), we were only able to test the change from 10.8 and 10.8.1, but we saw no appreciable difference in battery life. On both tests, we achieved what we consider to be the normal Apple-advertised operating time of 7 hours.

MacBook Air

In our final analysis, we’re taking a look at a 2011 13-inch MacBook Air (MBA) with a 1.7 GHz i5 CPU, 4 GB of Memory and a 240 GB OWC SSD. Its battery has a cycle count of 103 and is healthy according to OS X. Unlike the rMBP, with the MBA we were able to take the computer back to OS X Lion 10.7.4 and measure the change as we moved to 10.8 and 10.8.1.

To recap, all of our tests were performed by using a custom Automator application under battery-saving conditions: the screen at 50 percent brightness, keyboard illumination off, and all applications and services disabled except for WiFi. To keep the Mac running throughout the test, we disabled system and display sleep in System Preferences, and deactivated the screen saver.

Our Automator app performs the following actions:

  1. Open TextEdit, pause 10 seconds.
  2. Open Safari and navigate to a content-heavy website (, pause 20 seconds.
  3. Navigate to a second content-heavy website (, pause 20 seconds.
  4. Open Mail, pause 10 seconds to allow any messages to download
  5. Close all open applications
  6. Log a time stamp to a text file
  7. Repeat

Below are the results of our tests on the MBA, along with the results of our previous tests for the purposes of comparison.

Mountain Lion 10.8 Battery Life MBP MBA RetinaChart by The Mac Observer.

With the MBA, we experienced a similar pattern in battery life degradation to that of the MBP when moving from Lion to Mountain Lion, although the severity of the drop was not as large. On the MBA, we lost nearly an hour of running time, or about 16 percent, compared to a more than 33 percent loss on the MBP.

Like the MBP, things improved for the MBA after the upgrade to 10.8.1, but not enough to recover all of the initial loss. We gained back about 24 minutes of battery life on 10.8.1, leaving us about 30 minutes short of where it should be compared to Lion’s numbers.

MacBook Air Battery Life

Apple advertises “up to 7 hours” of battery life on the 13-inch MacBook Air. At 5 hours and 48 minutes of running time on 10.7.4, we are already a bit shy of that number. At 5 hours and 16 minutes after 10.8.1, the shortfall is even worse.

It’s clear that on all “traditional” MacBook models — meaning all MacBooks except for the redesigned MacBook Pro with Retina Display — Mountain Lion has caused a significant loss in battery life (although Ars Technica has some rMBP numbers to the contrary, which we were not able to replicate). Apple’s reluctance thus far to publicly address the battery life issue leaves us unsure of its cause, although theories include increased reliance on graphical elements in the interface, inefficient underlying code, or more background processes compared to Lion and previous operating systems.

Apple is already testing 10.8.2 with developers, although battery life is not addressed by the company in the update’s seed notes. We will continue to follow the progress of Apple’s Mountain Lion development and test new versions of the OS as they are released.

For now, although 10.8.1 did restore some battery life, users hoping for a quick solution to their battery life woes will likely have to wait a bit longer for an answer, if one ever comes at all.

Teaser graphic via Shutterstock.