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.