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 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.