According to the EPA's Green Power Challenge, Wells Fargo purchases 550 million kWh of green power annually, or 42 percent of its total electricity. Whole Foods is second, and deserves recognition because it is the only company to exclusively purchase electricity created from renewable sources. AMD, Liz Clairborne, AMD and Apple all buy 100 percent renewable power at one of their locations, but not for all of the company.

Some large companies made the list of top users even though they use less than 5 percent renewable energy, including Safeway, Dupont, IBM, HP, Kohl's, Lowe's, and Coca-Cola.

The EPA is challenging the Fortune 500 to double their usage of solar, wind, hydro, etc. energy to 5 billion kilowatt hours (kWh), or the equivalent of 400,000 homes.

These companies have convinced their shareholders that investing in renewable energy is smart business and are stabilizing the market by creating large and consistent demand. The companies are also protecting themselves from large swings in prices from fossil-fuel based energy providers.