On Wednesday, Lenovo, the Chinese PC maker, unveiled its smallest, most energy efficient desktop PC, called the ThinkCentre A61e or "Blue Sky," which is about the size of an average U.S. phonebook, according to the company.

The A61e ultra small form factor (USFF) desktop PC runs on 45-watt AMD Athlon 64X2 dual core and AMD Sempron single core processors, and starts at just $399 after mail-in rebate. Lenovo says users of its existing PCs can save as much as 50% in annual energy costs by making the switch to the A61e.

"The importance of maximizing energy efficiency and being environmentally conscious is touching all aspects of our daily lives, from the light bulbs we use to light our homes to the hybrid cars we drive to the green technology we rely on to run our businesses," said, Peter Schrady, vice president and general manager of Lenovo's Emerging Products Business Unit, in the release. "Lenovo is committed to providing an extensive menu of environmentally responsible, energy-efficient technology choices, and the ThinkCentre A61e is our signature item."

The PC is made of as much as 90% reusable/recyclable materials and its packaging is also made of 90% recyclables. In addition to its tradition power supply, the PC can be powered by a small solar panel.

The A61e is the first product from Lenovo to receive Gold status from the Green Electronics Council's Electronic Product Environmental Assessment Tool (EPEAT). EPEAT helps manufacturers gauge their products' conformance to a group of environmental criteria in eight categories, such as energy conservation, product longevity and the reduction/elimination of environmentally sensitive materials. The desktop PC also meets the U.S. Environmental Protection Agency's Energy Star 4.0 criteria, which ranks products' energy efficiency.

Lenovo claims organizations that deploy 50 or more A61e desktops can expect to save upwards of $1,000 in annual energy costs and some 10 tons of carbon dioxide emissions could be avoided. Large-scale enterprise deployments of 50,000 or more A61e desktops can save organizations more than $1 million dollars in yearly energy fees and 20 million pounds of carbon dioxide emissions could be cut.

Greenpeace International, an environmental protection group, in late June released the fourth edition of its Green Guide to Electronics, which ranks the world's leading electronics manufacturers on various environmental factors, and Lenovo and Dell tied for the second place spot behind Nokia. Sony and LG took the bottom two slots in the list.