A:Answer The monitor needs AC power if the device connects by Mini HDMI (you need a USB-C power supply, one is not included. Laptop chargers should be suitable). If the device connects to your computer by USB-C AND the USB-C port supports DisplayPort Alt Mode, then only one cable is needed from your laptop to the display. Bear in mind that powering the display off your laptop can reduce battery runtime, so keep your AC adapter handy.