Intel, the world's top chipmaker, and Nokia, the No. 1 mobile-phone maker, plan to lesson their respective impact on the environment, the companies said separately Monday.

While Nokia has joined the World Wildlife Fund's Climate Savers Program, Intel plans to buy 1.3 billion kilowatt hours a year of renewable energy certificates. That will make Intel the largest corporate buyer of green energy in the United States.

Buying renewable energy certificates is not, however, the same as directly buying and using renewable energy. Intel is making the purchase through Sterling Planet, a company that will then distribute the investment to a variety of green energy producers across the United States. The producers use wind, solar, hydroelectric, and biomass sources to produce energy that they then feed into the power grid. Those producers rely on the buyers of certificates to help fund their businesses, so Intel's investment is important to their success, said Matt Clouse, director of the Green Power Partnership at the U.S. Environmental Protection Agency.

Buying renewable energy certificates helps a company such as Intel support green energy even if it finds it difficult to directly buy green energy for use in its operations. Many green energy producers feed their power into the grid, but once they do, power users usually can't discern whether the energy they buy came from the green source or from a coal-powered plant, said Bill Calder, an Intel spokesman.

Some electric companies do have green power offerings, but a company such as Intel with multiple sites would have to work with various providers in multiple locations to try to buy green power from them, which is an expensive undertaking, especially in states where prices are set by a regulatory process, Clouse said. Buying the certificates can help companies track their environmental effect and hit environmental goals even if they find it cost prohibitive to directly buy and use green energy, he said.

Intel may have other reasons for making the investment beyond reducing its carbon footprint. "Many of these companies that are buying green power are customer facing, and they spend enormous amounts of money on their brand and product PR, and this is a way that is frankly a low-cost option to address the environmental aspects that affect their brand and image," Clouse said.

Intel is not revealing how much it will cost to buy the 1.3 billion kilowatt hours per year. However, Clouse estimated that Intel might be paying between $2 and $4 per thousand kilowatt hours, for a total yearly investment of $2.6 million to $5.2 million. "That's a pretty inexpensive media undertaking," he said.

Intel's investment in the renewable energy certificates is in addition to its regular energy costs, Calder said. But by buying the certificates, Intel is helping to fund the production of green power that is fed into the grid, he said. Ultimately, Intel hopes that other companies will follow suit, thus reducing the cost of green energy in the future, he said.

The volume of kilowatt hours that Intel agreed to buy per year equates to about 46 percent of its yearly electricity use in the United States, Calder said.

Also on Monday, Nokia pledged to use green electricity to power half of its facilities by 2010 and reduce overall energy needs of its sites by 6 percent by 2012, announcing that it has joined the WWF program. Nokia also plans to reduce energy wasted by mobile-phone chargers.

Greenpeace recently knocked Nokia from first place to ninth in a ranking of electronics makers. Greenpeace praised Nokia for its efforts to reduce the use of harmful chemicals in its products but said the company has done a poor job of supporting recycling programs in some countries.