Enterprises with an abundance of Windows XP desktop PCs and laptops can reduce power consumption costs and carbon dioxide emissions by half in switching to Windows Vista. When considering a total cost of ownership analysis for a Vista implementation, IT decision makers should understand how the two operating systems affect power consumption and consider the savings.
This is true. I have tried everything I can to get XP to use less electricity than Vista. I even installed XP on a Seagate Momentus 2.5" hard drive with an idle wattage of 2w but XP still idled at 72 watts vs an idle of 39 watts on a completley Identical system with vista.