Energy Star labels for the most energy efficient servers moved a step closer last week after the US Environmental Protection Agency (EPA) released a framework document outlining the key "building blocks" required to develop and implement the standard.

The new framework is subject to consultation until the end of August, with the EPA requesting feedback from interested parties on how to define computer servers, how to classify different server types, and which energy efficiency metrics should be used.

The document revealed that while the EPA would prefer to develop a single specification to cover all server types, it is aware this may be unviable. As a result, is considering a system of product "subcategories" that could exclude some servers from the scheme.

Moreover, the EPA also confirmed that, in an effort to accelerate the release of the new label, it is considering a tiered launch. A simple specification covering an area such as the efficiency of a server's power supply unit could be released first, followed by a more complex specification that covers "the energy consumed by the computer server system during a realistic workload".

In a letter to stakeholders, Andrew Fanara, programme manager for Energy Star product labelling at the EPA, said that the aim of the label is to make it easier for firms to select the most energy efficiency models available. " Setting an Energy Star efficiency level so that the top 25 percent of models in terms of efficiency can meet it offers the desired amount of selection and availability while also promising significant energy savings, cost-effective options and no compromise in performance," he argued.

John Madden of analysts Ovum said the move was likely to be welcomed by IT chiefs who are finding it increasingly difficult to navigate the different energy efficiency metrics being touted by various vendors. "There is sure to be [continued] confusion," he admitted. "But a government-developed and approved standard may help cut down on the noise between any competing standards or metrics that could arise."

However, Madden warned that the EPA may struggle to get agreement on the correct framework for the new metrics within the ambitious time frame it has set.

"They talk about the need for 'subcategories' to differentiate server types and capabilities - and that's where the discussions could get rather interesting," Madden predicted. "I can see server vendors each saying that all of their products have unique or distinct design or workload capabilities that need to be taken into consideration. What does that do to the discussion around standards?"