I did some power tests with Ubuntu and Windows a few years back to see which of the two that was least power consuming, back then I ended up running Ubuntu as I recorded a quite significant difference, up to 17% more battery time actually. Phoronix has now published a similar article where they compare the power usage of a desktop system with Windows XP SP2, Windows Vista, Ubuntu 7.10 and Fedora 8 Test 3. While Fedora consumed least power, Ubuntu actually consumed more than both Windows versions at idle, while both Linux distribution consumed more when under load. Not the most in-depth article but still a rather interesting read.
