The New York Times commissioned a study of energy use by data centers in the United States, and found that the energy usage is apparently much less than expected.
The report, by Jonathan G. Koomey, a consulting professor in the civil and environmental engineering department at Stanford University, found that the actual number of computer servers declined significantly compared to 2010 forecasts because of this lowered demand for computing and because of the financial crisis of 2008 and the emergence of technologies like more efficient computer chips and computer server virtualization, which allows fewer servers to run more programs.
The slowing of growth in consumption contradicts a 2007 forecast by the Environmental Protection Agency that the explosive expansion of the Internet and the computerization of society would lead to a doubling of power consumed by data centers from 2005 to 2010.
The report estimates that data centers worldwide consume about 1.3 percent of all electricity, and in the United States 2 percent of all electricity. Not bad given the widespread benefits (I’d love to see an analysis, for example, of the end-to-end carbon footprint of sending 1,000 messages over Gmail compared to mailing 1,000 letters).