The rate of growth in energy consumption by the world’s data centers has slowed significantly over the past five years. Contrary to earlier predictions, data centers used slightly more than 1% of all electricity consumed between 2005 and 2010, according to study recently completed and published by a California university researcher.

The study by Jonathan Koomey, consulting professor at Stanford University, attributed slower growth in energy consumption to a more widespread use of server virtualization and the recent economic recession.

The amount of energy the world’s data centers consumed grew by about 56% between 2005 and 2006, showing much slower growth in energy demand than between 2000 and 2005 – a period when data center energy consumption doubled – Koomey concluded.

He wrote that virtualization and other factors caused growth in the amount of servers installed in data centers to start slowing by early 2007. The 2008 financial crisis and the following economic slowdown, in addition to further progress in virtualization led to a number of servers installed in 2010 that was much lower than IDC’s 2007 forecast for the year.

In the US alone, data center energy use grew by about 36% during the last five years.

The amount of electricity each server consumed, however, grew quicker between 2005 and 2010 than it did between 2000 and 2005.

Data centers worldwide were likely to have consumed between 1.1% and 1.5% of all electricity consumed in the world. US data centers consumed between 1.7% and 2.2% of the total amount of electricity consumed in the country.

The US numbers are much lower than the Environmental Protection Agency’s report to congress in 2007 predicted. Koomey explained this by the smaller amount of servers installed over the past five years than EPA had expected.

The said EPA report estimated that the amount of energy consumed by data centers in the US in 2006 was 1.5% of total energy consumed in the nation. This report also estimated that that data center energy use in the US had more than doubled between 2000 and 2006.

The EPA predicted that national energy consumption by servers and data centers could nearly double by 2011.