Battery life on portable Macs running Mountain Lion improved slightly with the OS X 10.8.1 update, but still generally underperforms the same Macs running Lion. Since updating to OS X 10.8.1 from 10.8, we have conducted several unscientific tests on a variety of different Macs and found there is a minor improvement to battery life between the two versions of Mountain Lion, though most users probably won’t notice a significant change.

The hardest hit Macs tend to be any portable model with a Core i5 and Core i7 CPU from 2011 and 2012, including the MacBook Pro and MacBook Air, while, interestingly, Core 2 Duo machines seem to be less impacted with battery performance remaining mostly the same in Mountain Lion as it was in Lion.

MacBook Air 13″ Core i7 (mid-2012)
  • OS X 10.8.1 – 4:36
  • OS X 10.8 – 4:33
MacBook Air 13″ Core i5 (mid-2012)
  • OS X 10.8.1 – 4:48
  • OS X 10.8 – 4:31
MacBook Air 11″ Core i5 (mid-2011)
  • OS X 10.8.1 – 3:26
  • OS X 10.8 – 3:32
MacBook Air 11″ Core 2 Duo (late-2010)
  • OS X 10.8.1 – 5:45
  • OS X 10.8 – 5:47
Not all Macs have been impacted negatively by Mountain Lion however, a MacBook Pro 2010 model reported no noticeable change in battery life regardless of the version of OS X running on it.

Again, these are unscientific tests, with each Mac was running at 70% brightness doing normal computing tasks like browsing the web through Automator. The numbers on the MacBook Air 2012 model are a particularly dramatic change from the 8+ hours we were able to achieve in testing with that machine running Lion some months ago.

If you’re unsatisified with the battery life of your Mac running OS X Mountain Lion, you can do a few things to increase it, including:
  • Use a Flash blocker for Safari or the Click-To-Plugin in Chrome option to prevent Flash from autoloading on web sites
  • Dim the screen brightness to 50% or less
  • Dim or turn off the keyboard backlighting
  • Watch Activity Monitor for errant processes and disk activity
  • Do less CPU intensive activity while on battery
  • Disable Bluetooth
Some users have reported mixed success with resetting their SMC (System Management Controller). Also, some early reports of battery life being lessened were due to the Spotlight mds indexing process running after the initial upgrade from Lion, and for those users simply waiting it out led them to resume to normal battery expectations. There are also suggestions that disabling iCloud helps, but iCloud integration is a significant reason many people updated to Mountain Lion to begin with.
The battery issue has been noted by other sites, most prominently with a large thread on Apple Discussions, and MacObserver also ran similar tests with similar results, though their Macs seemed to last considerably longer than ours in general as demonstrated by their chart below.

Battery life drop in OS X Mountain Lion

There is currently no mention of adjustments to power management or battery life in the first OS X 10.8.2 developer build, but that may change with future builds.

What is your experience with battery life in OS X Mountain Lion? Has it improved or gotten worse with the 10.8.1 update? Let us know in the comments.