The USB interface is already used for charging smartphones, power external harddrives and other energy efficient units, but with a new specification set by the USB Promotor Group the USB interface will be capable of charging even notebooks.
USB Promotor Group has now set the USB Power Delivery Specifikation, which is a new standard for powering external units over USB. The current USB interface is limited and even if motherboard makers have found ways around this to squeeze out some extra watt from the USB port the USB PG has a much higher goal.
The USB Power Delivery specification will deliver 100 watt from a regular USB port – enough to charge a big notebook.
“We envision a significant move toward universal charging based on this specification, most notably for charging notebook PCs using standardized USB power bricks or when connected to USB hubs and desktop displays that integrate USB Power Delivery capabilities,”
USB Promotor Group has started approving companies for product development according to the new USB specification and as implied in the press release there is a wide assortment of potential products. Among others, USB monitors that will not only transfer audio and video, but also power over a single USB cable.
USB Promotor Group has developed new, more powerful USB cables to handle the higher power output, but current cables are backwards compatible with the new specification. Although with lower charge capacity.
Source: USB.org (PDF)