Impact on battery of using external monitor?

Might seem like I silly question...

Does anyone have any kind of idea as to the impact on battery usage of being connected to an additional monitor?

I'm assuming there is some, and that higher resolutions on the external monitor will also impact battery life along with things like brightness etc?

This is with the MacBook running on battery, not being used in clamshell mode.

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4 Answers from the Community

  • Best Answer:

    In short, there IS a negative impact on the battery usage of your laptop when you use an external display.

    How much of an impact depends on what kind of Macbook you have. If your MacBook has two video cards, like the Retina MacBook Pro, then yes it will use a lot more battery to have an external display. The reason is because when you connect an external display, even if you close the laptop and use it in clamshell mode, the laptop automatically switches from an integrated video card (this uses much less power) to a more powerful, discrete video card (this uses a lot of power). The laptop does this because the integrated video card isn't very powerful and can't process video for the 3K Retina display AND an external display smoothly.

    If your laptop DOESN'T have a second video card, then connecting an external display will still drain the battery more quickly than normal, but not as quickly as a MacBook with two video cards. Similar to before, this is because the video card in your MacBook has to work harder to process a video signal to both the laptop and the external display. Also, using a MacBook in clamshell mode will still cause the video card to work harder than normal, although again, not too badly.

    Hope this helps!

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  • An external monitor will be drawing it's own power off the wall, so brightness of the external doesn't matter. Since the additional pixels from the monitor will require extra computing power from your graphics chip to display, it will, overall, reduce your battery life.

    I believe that Apple monitors have a power supply for Macbooks built in, so if that's the external you're connecting to, you should be good.

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  • Technically the battery life should stay consistent because your computer isn't actually powering the external monitor, only sending a signal to it. Your external monitor should plug into the wall seperately having its own operating power source.

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  • From my experience, it somehow makes the battery last longer.

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