"We're achieving a very significant amount of battery savings, " said Microsoft's principal programme manager Ruston Panabaker, who would not be drawn on exactly how much overall battery life Windows 7 will save.

BBC: Microsoft shows 'faster' Windows

Since the 2010 Office suite is not as close to the end of its life cycle as Windows 7, and we expect the revenues from this segment to continue to grow.

FORBES: Office Will Need To Prop Up Microsoft's Earnings Ahead Of Windows 8

In other words, a similar battery life rating as other Ivy Bridge Windows 8 Ultrabooks, except this time, there are a lot more pixels to light up.

ENGADGET: Toshiba KIRAbook hands-on (video) Hands-on