A little less than a year ago, we learned that the USB Implementers Forum, the governing body behind the interface standard, was working to boost output power to 100W. The USB Power Delivery specification is now complete, and you can read all the sordid details in the updated USB 3.0 spec. The Power Delivery PDF weighs in at over 300 pages, so we'll give you some highlights.
The most important element of the new specification isn't the increase in maximum power, but a change in how that power can be transmitted. Current USB implementations allow power to flow only from the host to connected devices. The USB Power Delivery spec allows current to flow in either direction. Devices like laptops will be able to charge their batteries over the same ports they use to power external peripherals.
More power is on tap in the new specification, of course. There are five different power profiles, starting with a base level that offers 5V on 2A for a total of 10W. The second profile adds a 12V source at 1.5A, and the third boosts 12V power to 3A. The fourth and fifth profiles add a 20V line at 3A and 5A, respectively. Only the fifth profile is capable of delivering 100W. According to the USB-IF, devices designed for the lower profiles should work just fine in ports that support the higher profiles. Even the base profile more than doubles the power available via a standard USB 3.0 port.
Despite dramatically ramping up the wattage, the USB Power Delivery specification uses the same physical connectors as existing products. Data and power continue to share the same cable. New cables will be required to carry the extra juice, of course, but your old thumb drive will still work in the high-power ports.
USB 3.0 Promoter Group Chairman Brad Saunders expects the Power Delivery spec to enable "a significant move toward universal charging," and I hope he's right. So many devices rely on USB power these days, and no one likes bulky wall warts.