How much power can a USB 3.0 port supply?

4.5 watts
Also, with a USB 3.0, it can provide up to 900mA or 0.9A, which translates into 4.5 watts. These power output specifications are a rating based on the 5 volts from each standard output. However, the USB 3.0 dedicated charging and charging downstream ports provide up to 1,500 mA or 1.5A, which translates into 7.5 watts.