Wondering how much electricity the Internet consumes? According to a news report on Slashdot it's 5.3% of the global demand, while in the U.S. it's already 9.4%.
These numbers come from a research by David Sarokin from Uclue:
Worldwide, that's 868 billion kilowatt-hours per year. The total includes the energy used by desktop computers and monitors (which makes up two-thirds of the total), plus other energy sinks including modems, routers, data processing equipment and cooling equipment.