Microsoft has unveiled the long-awaited Power Cover for its Surface tablets, which acts as both a keyboard as well as an external battery. The new cover is slightly thicker than the 5.3mm Type Cover, and will reportedly add up to 30Wh to the tablet, or up to 50 percent more battery life. With the Power Cover, the new Surface Pro supposedly lasts two and a half times longer than the original tablet.

The typing experience is supposedly very similar to the original Type Cover, but the new cover is covered with a soft fabric. Just like the other cases, the new Power Cover snaps onto the tablet to create an almost book-like form factor. The Power Cover will cost an additional $199.99, significantly more than the $119.99 Touch Cover 2 and the $129.99 Type Cover 2. There's no official release date yet, but the new Power Cover is projected to be available early next year.

An important theme of the Microsoft Surface 2 event was battery life, especially with the switch to the energy-efficient Haswell processors with the new tablets. The new Power Cover plays into this theme, stretching battery life beyond the improvements given by Haswell alone.