Dell today is reporting that the company has already met its goal of carbon neutral offices and work sites by the end of 2008. Although Dell's headquarters is 100 percent powered by renewable energy and company buys power from renewable sources whenever possible, there just isn't enough of it to go around, unfortunately.

So, carbon credits to the rescue!

There is not enough green energy available for all of Dell's requirements, so for the other 80 percent, Dell buys regular "brown" power, Parker said, plus enough renewable energy credits to offset that power's carbon emissions. Those credits subsidize purchases of renewable energy by other organizations, in places where more green power is available.

Dell's preference for renewable energy isn't just about global warming or public relations. Buying green power at a predictable cost can serve as a hedge against rising oil prices.

The company also said it has cut its energy use with more efficient lighting, modern climate control systems and software that shuts off idle office computers after hours, for a savings of $3 million a year, or about 5 percent of its annual energy bill.

Dell also made a splash last week by rolling out the Studio Hybrid desktop, the company's lean, green Vista-running machine.