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Comment by lathiat | Hacker News Reader

Watch your backlight level, which auto adjusts to the room light level.

"When comparing battery life, remember that screen brightness makes a huge difference!

On an M1 MacBook Air sitting idle on the KDE desktop, you will get around 7 hours of runtime at 100% brightness, and 23 hours of runtime at the minimum (not zero) brightness.

Even keyboard brightness matters! Those numbers are with the keyboard backlight turned off. If you turn it on at max, even with the screen left at minimum, your runtime goes from 23 hours down to just 14 hours.

So please don't ask us what battery lifetime to expect while doing a certain task and expect a single answer!"

https://social.treehouse.systems/@AsahiLinux/110548137464042...

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Yes, I should have mentioned I always have keyboard backlight turned off [1]

I’ve suspected something to do with screen brightness in the past also. System log was often full of messages from the brightness adjustment/monitoring daemon, which raised my suspicions, but I think it might just have been normal behaviour at the time.

However the mystery power draw seems to happen independent of screen backlight setting. ie: when the problem is happening, turning backlight right down will reduce power draw a bit, but it’ll still be high. On other occasions, even with the screen brightness at 100% I’ll still get “normal” power draw. I’ve experimented with turning off brightness auto-adjustment too, with no effect.

[1] Keyboard backlight is very annoying at night when trying to watch a movie or something, and Apple made it difficult to toggle on and off on recent Macs by removing the hot key for it. So I’ve learned to just live without it.

Keyboard brightness - you can put the control into control center and then it’s two clicks to get to a slider for it.

Not awesome, but for the relatively rare times I want to change it manually, it’s been acceptable.

Yeah I do have that, but I usually find it too slow/annoying to have to use the mouse to turn it on and off. It was so much quicker and easier when there was an F-key to instantly do it.

Maybe one day I’ll get around to making an app to map it to an F-key again, which has been on my todo list for a long time…

Have you got the automatic adjustment off? The night time thing hadn't bothered me.

https://support.apple.com/en-au/guide/mac-help/mchlp2265/mac

You are correct. Even plugging in my gaming mechanical keyboard makes a noticeable difference.

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