"If Vista is run in full Aero mode, with none of the Vista-provided power management settings turned on, it is likely to demand more power, and have an impact on battery life," said Dell spokesman Ira Williams, in an e-mail interview. "That said, if you run Vista in battery-optimized mode (using a non-3D interface), we would not expect the battery life to be significantly different from XP in that scenario."A Microsoft spokesperson also told the site, "Although it is true that the Windows Vista Aero theme and components can use more resources than previous versions of Windows, the relative impact to battery life is minimal." And a Gateway spokesperson added, "We've done extensive testing, and we haven't seen [shortened battery life]. While it is true that Vista has higher system requirements than XP, it also has more sophisticated mechanisms to allow for power savings."
Interestingly enough, we found almost no measurable impact on power consumption when running Vista's Aero look on various desktop graphics cards.