USB Power Delivery
The USB Power Delivery (PD) specification enables power delivery up to 100W but how much power exactly is provided depends on the device. For self-powered Thunderbolt 3 devices with a second Thunderbolt 3 port, the minimum is 15W, which is enough to use a bus-powered device on the second port. Currently, depending on the model, we provide products with 15W, 27W, 60W and 85W.
How much power is needed?
It depends on the computer, the peripherals and what you are doing with it. In general, 27W is enough to maintain or slightly recharge the battery when the computer is not under load and 60W is enough to recharge the battery even when the computer is under moderate load. For more details, see the diagrams below and check out our test results when recharging a MacBook Pro.
15" MacBook Pro with 87W PSU
The 15" MBP comes with a 87W power supply, because it has four Thunderbolt 3 ports and needs to provide a lot of power in case all of the ports are occupied by bus-powered peripherals. For example, with the PSU connected to one of the ports (87W), two bus-powered Thunderbolt 3 devices (2 x 15W) and one bus-powered USB device (7.5W), that will leave about 50W for the computer (87W - 15W - 15W - 7.5W = ~50W).
In the scenario above with three bus-powered devices connected to the computer, 60W is insufficient. However, if you are using a product like our Thunder3 Dock Pro and connect one bus-powered Thunderbolt 3 device to the second Thunderbolt 3 port on the docking station, use the built-in USB ports for the USB drive and do not connect any bus-powered devices directly to the computer, 60W as provided by the docking station is enough to power the computer.
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