Power, Pollution And The Internet

Worldwide, data centers use about 30 billion watts of electricity, roughly equivalent to the output of 30 nuclear power plants. Only 6 percent to 12 percent of the electricity is used for powering the servers to perform computations. The rest was essentially used to keep servers idling and ready in case of a surge in activity that could slow or crash their operations. 

NYT: Power, Pollution and the Internet