From a New York Times Magazine article about gigantic data centers and the power it takes to run them:
While it once took 30 to 50 years for electricity costs to match the cost of the server itself, the electricity on a low-end server will now exceed the server cost itself in less than four years — which is why the geography of the cloud has migrated to lower-rate areas.
According to Jonathan Koomey, a scientist at Lawrence Berkeley National Laboratory, the internet consumes 1 to 2 percent of the world’s electricity.