Industry groups and government agencies from the US, Europe and Japan have reached a basic agreement on how to measure the energy efficiency of data centres. The agreement is seen as significant because it establishes a common metric that different types of data centres, in different parts of the world, can use to report their level of energy efficiency. That could provide a yardstick for companies to assess the efficiency of their own data centres, and also to gauge the effectiveness of energy-saving techniques employed by other facilities.

The agreement is unusual for its level of international cooperation. Orchestrated by the Green Grid, an industry consortium in the US, the agreement is backed by the US Department of Energy, the US Environmental Protection Agency, the European Union Code of Conduct and the Japan Ministry of Economy, according to a statement from the Green Grid.


The participants have agreed to adopt Power Usage Effectiveness, or PUE, as their "preferred energy efficiency metric," the statement says. PUE, which was developed by the Green Grid, divides the total energy consumed by a data centre by the amount of energy used to power the IT equipment. The result shows how much energy is being lost to mechanical and electrical systems.

The choice of PUE is no surprise. It has emerged as the most popular metric for measuring data centre efficiency, and some large companies, notably Microsoft and Google, have been publishing PUE numbers as a way to show off the efficiency of their newest facilities. But there is no standard method for calculating PUE, and the groups participating in the agreement still have some work to do, in defining how the total energy consumed by a data centre should be measured, for example. They are also expected to develop and define further efficiency metrics.

"A global task force with representatives from each of the above mentioned organisations will continue to move this initiative forward and reconvene later this year to evaluate progress," the Green Grid says in the statement.

The agreement follows several meetings of stakeholders and interested parties. In January, representatives from the EPA met with several data centre industry groups from the US, including 7x24 Exchange and ASHRAE (The American Society of Heating, Refrigerating and Air Conditioning Engineers). The EPA then took the input from those groups to a meeting of international representatives on February 2. A copy of the February 2 agreement (PDF) was quietly posted on the Green Grid Web site this week.

"These guiding principles are meant to help drive a common understanding of energy efficiency in data centres," the EPA's Energy Star for Data Centres program said in a note to its member companies. The Green Grid is understood to be in talks with representatives from China, India and other big markets to bring them on board with the initiative as well.

The agreement comes as energy use in data centres comes under increasing scrutiny. Rising energy costs and the amount of powerful IT equipment that has been added to data centres in recent years has made them a cost centre on the radar of senior executives.

Environmental pressures, including new carbon emissions rules that have been introduced in Europe and will likely come eventually to the US, are also forcing companies to be more aware of their data centre energy use. In the US, the Securities and Exchange Commission published new guidelines last month about the risks related to climate change that public companies must disclose to investors. John Stanley of the Uptime Institute wrote a blog post about it this week.

"Overall, the ruling provides businesses, including those in the IT and data centre industries, yet another reason to keep energy use and environmental performance on their radar at the highest levels of management," he wrote.