Now this is from MS themselves, so obviously they’ll have picked sites which work best for IE, but most importantly it shows that there is a huge variability in the amount of power each browser uses. This is not only useful for laptop users who want to maximise their batteries, but also for the global power consumption, considering the browser is what most people use continuously on their computer.

Browser Power Consumption—Leading the Industry with Internet Explorer 9 – IEBlog – Site Home – MSDN Blogs.