The Energy Star 5.0 specification will help customers identify the most power-efficient PCs and PC-related devices, including laptops, desktops and monitors, when making purchases. Products are identifiable with an Energy Star label attached to the devices.

The Energy Star specification pushes higher power-efficiency requirements in consumer electronics by setting power allowances. The EPA develops separate Energy Star specifications for more than 60 devices including TVs, refrigerators, servers and light bulbs.

With the Energy Star 5.0 specification, the EPA is trying to raise the power-efficiency bar in PCs by tightening requirements for computer makers to earn the Energy Star label. Some companies, including Apple, Dell, Lenovo and Hewlett-Packard, have already started shipping PCs that adhere to Energy Star 5.0 specifications.

"We believe that products that meet the Energy Star 5.0 requirements will use 30 percent to 60 percent less energy than the standard [devices] on the market, which are largely 4.0 models," said Katharine Kaplan, a spokeswoman for the Energy Star program at the EPA. If all computers sold in the U.S. meet the latest requirements, savings in energy costs could reach US$2 billion per year, she said.

The new energy specification should also help reduce energy bills, depending on how the users shut down systems. Power consumption of PCs accounts for a fraction of the home electricity bill compared to heating and lighting, but every dollar adds up, she said.

"We really care about delivering dollar savings to consumers. We know that is important, perhaps more now than ever. But we're also really concerned about global warming," Kaplan said.

Specifications have been set for PCs, laptops and other devices, with power allowances available at Energy Star's Web site.

The kilowatt-per-hour allowance for laptops has been set between 40 kilowatts per hour and 88.5 KwH based on three modes: standby, active and sleep modes. The laptop categorization takes into account the CPU, the number of cores, and other hardware including graphics cards. The power allowance for desktops has been set between 148 KwH and 234 KwH. The EPA has also set power allowances for monitors, small-scale servers like media servers and enterprise devices like thin clients.

The EPA hopes to soon launch specifications for home networking equipment like routers and modems, Kaplan said. The agency is also investigating enterprise-level UPS (uninterruptible power supplies) and storage energy specifications. The EPA in May launched the first Energy Star specifications for enterprise servers.