What happens if, on a MacBook Pro 16" M3 2023, both MagSafe and a Thunderbolt Dock, such as the CalDigit TS4 Thunderbolt 4 Dock, which delivers 98W (might not enough if the MacBook is used heavily as the MagSafe Pmax=140W) are plugged in? Will one of the two power inputs be ignored? Is this safe?


1 Answer 1


I'm sure this has been asked before, but yes, it will use the power source that can provide the most power.

This question contains a quote from a now-defunct Apple Support page:

  • Your MacBook Pro draws power from only one power supply, even if more than one is attached—so using multiple power supplies won't speed up charging.

  • If you connect multiple power supplies to your MacBook Pro, the one that provides the most power will be used, regardless of the order in which you connected them.

  • Not a clear answer as MagSafe is not mentioned. I can only infer that MagSafe will take priority over USB-C PD because 140W (MagSafe) > 100W, which is what most USB-C PD are able to output so far. There should be a clear-cut answer on this as I've seen motherboards die with powered USB hubs and such.
    – lucasart
    Commented Apr 18 at 14:16

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