The energy consumed by data center servers and related infrastructure equipment in the U.S. and worldwide doubled between 2000 and 2005, according to a new study.

A jump in the volume of servers in data centers is accountable for 90 percent of the growth in power consumption. The total 2005 electric bill to operate those servers and related infrastructure equipment was $2.7 billion in the U.S. and $7.2 billion worldwide.