The average data center uses the equivalent of about 2 tons of coal (or 80 barrels of oil) per day; a datacenter with 2,500 servers uses enough electricity in a month to power 420,000 homes for a year. A 30,000 square foot data center with 1,000 racks needs $4.2 million a year to power and cool the computing processing power you are using (including maintenance and amortisation costs).

Those figures are from HP, Sun, the Carbon Trust and Forrester Research, and make disturbing reading.

The result the of last example would also generate 44,000 tons of carbon into the atmosphere; in the EU you can offset that using the Emissions Trading Scheme, but it would cost you an additional 700,000 Euros to do so.