Expecting some holiday money? Thinking of rushing out to spend it on a shiny new MacBook Pro? After months of testing, our colleagues down the hall at Consumer Reports say, maybe don’t do that just yet.

For the first time, Consumer Reports says, it is not recommending that consumers buy the most recent generation of MacBook, which was released this fall.

It’s not due to the dongles, although those are proving to be a pain in the butt for many Mac users. Nor is it even about the loss of the once-beloved startup chime (alas). Instead, it’s all down to the batteries.

Apple promises that the new line of MacBook Pro machines should get about 10 hours of use between charges… but many users, including CR testers, aren’t getting consistently solid — or in fact, consistent at all — results:

For instance, in a series of three consecutive tests, the 13-inch model with the Touch Bar ran for 16 hours in the first trial, 12.75 hours in the second, and just 3.75 hours in the third. The 13-inch model without the Touch Bar worked for 19.5 hours in one trial but only 4.5 hours in the next. And the numbers for the 15-inch laptop ranged from 18.5 down to 8 hours.

Usually in laptop testing, CR writes, battery life varies from trial to trial by maybe 5%, and you can average the numbers together reasonably. But with the MacBook Pro, the results are so completely all over the map that an average is meaningless.

CR asked Apple to explain, but the company has declined to comment on the results for the time being, saying simply, “Any customer who has a question about their Mac or its operation should contact AppleCare.”

For more about the methodology CR used, and why it’s such a strange departure for the MacBook line, check out their story.

Update, 1/12/15: After Apple updated the software for the MacBook Pro, Consumer Reports has changed its recommendation.

New MacBook Pros Fail to Earn Consumer Reports Recommendation [Consumer Reports]

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