Since this story was originally posted, it has been updated to including additional information about the Lenovo ThinkCentre A61e PC.

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 percent in annual energy costs by making the switch to the A61e.

Lenovo A61e ThinkCentre Desktop PC

"The importance of maximizing energy efficiency and being environmentally conscious is touching all aspects of our daily lives, from the lightbulbs 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 percent reusable/recyclable materials, and its packaging is also made of 90 percent recyclables. In addition to its tradition power supply, the PC can be powered by a small solar panel. The Advanced Energy Group manufactures the solar panels, and more information about the A61e's solar power options is available on its website.

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.

"More than ever, companies are focusing on controlling costs, whether it's in the IT department or any other," said Bob Kuehner, Lenovo's worldwide marketing product manager, emerging products. "When purchasing PCs, managers should consider the total cost of PC ownership (TCO), not just the acquisition cost. Lenovo's new ThinkCentre A61e ultra small form factor desktop PC offers that TCO through its price point, ThinkVantage Technologies and energy efficiency. It also offers several other benefits including space-saving design and whisper-quiet acoustics. All of these separate the Lenovo ThinkCentre A61e desktop from other desktop PCs in the market."