According to a test conducted by Ars Technica, there may be evidence that Apple's new operating system is draining batteries significantly faster than the previous OS X Lion, as the publication's test unit lost some 38 percent of runtime after having installed Mountain Lion.
In a series of unscientific tests, a MacBook Pro with Retina display was run on battery power both with and without Mountain Lion installed. Ars was able to hit just over eight hours of runtime with Lion and the integrated Intel HD4000 GPU, meaning the computer wasn't leveraging the discrete and power-hungry NVIDIA GeForce GT 650M. With Mountain Lion installed and using the same settings, however, runtime dipped to around five hours.
The test was conducted a number of times, each using the same applications under what was described as a "daily workload." Being used actively were Safari, Chrome, Twitter, iChat, TextEdit, Photoshop, Mail and Outlook, among others while Dropbox and gfxCardStatus ran in the background. As far as systems settings, Wi-Fi was activated while Bluetooth was turned off and screen brightness was set to half-strength.
Mountain Lion's Activity Monitor was used to check CPU usage and, while there were occasional spikes when reading or writing files, loading web pages or other user-initiated operations, the processor was usually below five percent capacity. This is contrary to one account from an Apple Communities forum member who noted a heightened CPU temperature when the computer was idle.
A 49-page Apple Support Communities thread first started on July 25, the day Mountain Lion was released, chronicles a number of battery issue complaints from users who recently installed Apple's new OS.
A few forum members suggested the problem lies with one of Mountain Lion's new features like Power Nap, while others have found limited success with resetting their machine's system management controller, but a legitimate fix has yet to be discovered.
Interestingly, only certain machines are affected by the purported battery drain issue and some users are even reporting their battery life increased after installing the new operating system.
Apple has yet to release an official statement, but a number of forum members affected by the issue claim Apple representatives reached out to obtain system information in an attempt to remedy the problem.