On the latest macOS Sierra beta, when a Mac’s display is set above 75% brightness—or at least 13 out of 16 notches—a new item called “Display Brightness” is listed under the battery menu.
Clicking on “Display Brightness” lowers the Mac’s brightness to 75%. Likewise, when we updated a new MacBook Pro to the fourth beta of macOS Sierra 10.12.3, the display’s brightness was automatically lowered to 75%. This is the same brightness level as Apple used during its latest MacBook Pro battery tests.
Many notebook users have long known that screen brightness can have a big impact on battery life, and now Apple’s software will point a finger at its hardware. As weird as that is, I think macOS should provide as complete of a picture as it can when it comes to battery range.