The US Environmental Protection Agency has launched its Energy Star program for data centres, meaning companies can start applying today to see if their facility qualifies for an Energy Star logo. The government is concerned about the level of energy consumption by data centres. In 2006 they were already estimated to account for 1.5 percent of the nation's total electricity use, equivalent to about 5.8 million homes, or 5 percent of the US housing stock, according to an EPA report (PDF) to Congress.

The Energy Star program aims to give companies a greater incentive to make their data centres more efficient, because they will be able to use the Energy Star logo in marketing materials as a sign of their "greenness," for example. It should also give companies a way to compare their energy efficiency against that of peers in the same industry, said Mark Harris, vice president of product marketing with Modius, which makes tools for real-time monitoring of data centre energy use.

To earn the logo, data centres must be in the top 25 percent of their peers in energy efficiency according to the EPA's energy performance scale, the EPA said in a statement. "By improving efficiency, centres can save energy and money and help fight climate change," the agency said.

Efficiency levels will be calculated mainly using the PUE (power usage effectiveness) metric, which measures the total power supplied to a data centre, divided by the amount that actually reaches IT equipment, as opposed to being lost to cooling systems and inefficient power supplies. Customers that want to apply for the logo must use the EPA's online tool, Portfolio Manager, which will assign them an efficiency score between 1 and 100.

"Before being awarded the Energy Star, a licensed professional must independently verify the energy performance of these buildings and sign and seal the application document that is sent to EPA for review and approval," the EPA said.

While it was developed in the US, other governments have expressed an interest in adopting the Energy Star for data centres program, much as they use the Energy Star logo for other types of products. The system has come in for some criticism but is seen as a necessary first step. Harris expects the program to eventually be revised with a metric that goes beyond PUE to more accurately reflect the efficiency of a particular data centre.

"It may not be perfect but at least it allows you to compare your imperfect number with peers in your group," he said. "PUE is an easy enough number to come by, we do it for customers every day. So it's a good place to start."

The EPA has been trying to come up with a better metric for calculating efficiency based on the amount of computing work a data centre actually performs. But there is much discussion in the industry about how to achieve that. Those who hesitate to take part in the program will often be those companies that are afraid to reveal how they rank alongside their peers, Harris said. That in itself may give them added incentive to improve their efficiency.

The Energy Star program applies to standalone data centres and to large data centre facilities housed in other buildings. More information is here at the EPA's website.