According to CR, laptop battery life “varied dramatically from one trial to another.” Consumer Reports purchased each of its three machines at retail, with no interaction with Apple, to ensure it tested the same machines that consumers would purchase. The findings are worth quoting directly:
The MacBook Pro battery life results were highly inconsistent from one trial to the next.
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. Those were just a few of the results; we tested battery life on these laptops repeatedly.
Typically, a laptop’s battery life may vary from one trial to another by less than 5 percent. To arrive at our final battery life score we average those measurements together.
However, with the widely disparate figures we found in the MacBook Pro tests, an average wouldn’t reflect anything a consumer would be likely to experience in the real world. For that reason, we are reporting the lowest battery life results, and using those numbers in calculating our final scores. It’s the only time frame we can confidently advise a consumer to rely on if he or she is planning use the product without access to an electrical outlet.
Consumer Reports goes on to detail how they test and notes they ran battery tests in both the shipped version of macOS as well as the recent 10.12.2 update. Performance did not change. They then tried testing under Chrome instead of Safari and saw much better results, even though Chrome has a reputation for being a battery hog. Unfortunately, these results aren’t comparable to the rest of their data set, since CR always tests with the default browser, and there’s no explanation for why Safari would have such varying results.
My own guess is this: Something is clearly broken in Apple’s power management stack. The company removed the “Time Remaining” information from macOS 12.2.2, claiming that providing an estimated Time Remaining was too difficult because of the way CPUs enter and exit power states. This seems rather unlikely, given that Microsoft still manages to give a Time Remaining estimate on Windows 10 laptops, and they use exactly the same x86 CPUs that Apple does. There’s also no reason that Apple couldn’t calibrate its “Time Remaining” metric by basing it on how the CPU transitions in and out of power states over a longer period of time. Over the long term — and keep in mind that to a CPU operating at multiple GHz, five seconds is ‘long term’ — the chip’s activity patterns should average out. Very few people start rendering a mammoth 3D project, switch to aggressive 3D gaming, and then switch back to some light desktop work within 5-10 seconds.
Consumer Reports is the gold standard for reviewing products and methodologies — if they’re picking up such drastic problems with three different systems, it’s a good sign that Apple has a serious problem it either can’t find or doesn’t want to admit.