The final specification will be published on the EPA's Web site on Friday evening, said Andrew Fanara, who heads the product programs. The first qualifying servers may be listed on the site as soon as this weekend, he said.
The EPA has been working on with server makers for more than a year, trying to reach agreement on the types of servers to be covered and the criteria included.
The final program covers servers with up to four processor sockets and at least one hard drive. Blade servers are not included but may be added to the program in the next two months, Fanara said.
The main criteria are the efficiency of a server's power supply and the amount of power consumed at idle. Vendors must also publish power and performance data in a standard way for qualifying models and configurations.
The program will be used mainly for industry-standard x86 servers, which account for the vast majority of shipments, though the specification doesn't specify a particular processor architecture, Fanara said.
The EPA expects approximately 25 percent of servers shipped to qualify for the Energy Star logo, he said.
The specification has been criticized by some for measuring idle consumption only, rather than the work done for a given amount of energy. The EPA has called it a useful first effort that gives customers a starting point to compare the efficiency of different systems.
The EPA says power supplies can vary considerably between server models, and that many servers still spend much of their time doing little or no work despite the wider use of virtualization.
The agency is working on a "Tier 2" specification that will aim to measure work done. Fanara said it hopes to publish it by Jan. 1 next year, although he acknowledged that timeframe is ambitious. The biggest challenge isn't a technical one but reaching consensus among the players involved, he said.
Critics have also noted that resellers may reconfigure systems in the channel, by adding more memory and disk drives, for example. The EPA will rein in such behavior as much as it can, but customers should check that the configuration they receive is the one that qualified for the program in the first place.
The Energy Star program has been successful in the past, covering more than 50 types of products including computer monitors, ceiling fans and washing machines. The EPA has said the server program was the hardest product category it has tried to do.
It is now working on an Energy Star for storage equipment, a first draft of which could be covered in the coming weeks, and eventually it plans to tackle network gear as well.
Energy efficiency has become a focus for many companies because the power and cooling capacity has become strained at their data centers. The increasing power and density of servers has made them a significant operational cost for many organizations, which also face pressure to reduce carbon emissions.
The Energy Star logo will appear alongside the system specifications sheet on each vendor's Web site. The EPA will also publish qualifying models and configurations on its Web site.
Vendors are so keen to tout the efficiency of their products that some will issue press releases in the coming days touting their Energy Star status, Fanara said. The specification hasn't changed significantly from the last issued a few weeks ago, so vendors have had a pretty good idea which products would qualify.