InfoWorld has some interesting stats on datacenters and the power they consume from McKinsey and Company.

$11.5 billion - The total estimated energy bill for datacenters come 2010, up from $8.6 billion in 2007. Driving that figure: The installed server base is expected to grow by 16 percent to as many as 43 million machines worldwide; energy consumption per server is increasing by 9 percent; and energy prices have risen by an average of 4 percent, according to McKinsey. That, of course, means that if you're feeling some pain now from high energy prices or insufficient power, it's going to get worse if you don't make some changes.

Another interesting stat is $1,870, the "annual operating expense for powering and cooling a single midtier ($2,500) server in a tier III datacenter."