Consumer Reports Says a Web-Cache Setting May Have Been to Blame for Inconsistent Results in Testing

Update 01/13/17: Consumer Reports says Apple's fix has solved the problem it found with the new MacBook Pro line-up and has re-rated the systems as "recommended." CR said the units it tested averaged 15-19 hours of operation under a single charge with the fix applied. (Results were as low as 3.75 hours in the previous round of tests.) The update is not yet available to all Mac users.

Apple says a flaw in its new line-up of MacBook Pros that impacted expected battery life in tests by Consumer Reports — battery life was so inconsistent that CR declined to recommend any of the new systems —  was a bug in Safari that "does not reflect real-world usage." Nonetheless, Apple has provided a fix for the issue that is available now to beta software users, and CR is re-evaluating the systems.

The bug was said to be revealed as CR described its testing methodology to Apple, which includes turning off local caching of web pages, so that when CR hits the same page multiple times, it is reloaded from an internal server as though it's being accessed for the first time. Apple said that setting "triggered an obscure and intermittent bug" that has been fixed.

"This is the best pro notebook we've ever made, we respect Consumer Reports and we're glad they decided to revisit their findings on the MacBook Pro," Apple said in a statement published by CR. For its own part, CR promised to update its findings once it has a chance to do a comprehensive retest of the MacBook Pro's battery life.

But the company did note that MacBook Pro users have complained about short battery life in user forums, and it's unclear whether any problems outside of the testing labs will be addressed by Apple's current fix. (For a summary of the issue, see ExtremeTech's coverage from early December.)

The new software update is available now to Mac users in Apple's Beta Software Program, and should be made available to the broader universe of users in the coming weeks.