If you're like me, Google is usually your first stop when looking for information. Google also manages my email, calendars, contacts, and RSS feeds. Keeping these services running requires a lot of computing power and electricity usage. When thinking about how many server farms, data centers, routers, switches, cooling systems, etc... are required to keep all of this running, it becomes apparent that this is very energy intensive.
No one knows for sure just how much electricity Google uses to run its operations, but people speculate nonetheless. I found a blog post that tried to quantify just how much electricity Google consumes and how much CO2 this translates to. From the blog post, it looks like Google receives its electricity from nuclear and hydro plants, but still consumes more than most countries!
Interesting read. Check out the post here for more info.