Wal-Mart is purchasing solar power equipment from BP Solar, SunEdison LLC and PowerLight, a subsidiary of SunPower Corp. The equipment will be installed in California and Hawai'i in 22 locations, including Wal-Mart stores, Sam's Club warehouse stores and a distribution center.

"We are taking aggressive steps toward our goal of being supplied by 100 percent renewable energy," Wal-Mart's vice president for energy, Kim Saylors-Laster, said. "The pilot project is yet another example of Wal-Mart's commitment to making decisions that are good for business and the environment."

The world's largest retailer, headquartered in Bentonville, has been working in different ways to generate less waste and use less energy. The company has opened two Supercenters designed to use 20 percent less energy than other Supercenters. The stores use natural light whenever possible and employ energy-saving heating and cooling systems and construction materials.

The company also is putting environmentally friendly items on its shelves, such as compact fluorescent light bulbs.

In the latest push, SunEdison will provide the four solar power systems in Hawai'i and four in California, while PowerLight and BP Solar will each supply seven systems in California.

Wal-Mart didn't announce how much it will spend on the venture.

The company said it is trying to determine whether it can harness the sun to provide electricity to all its stores. Once all the equipment for the test is up and running, Wal-Mart estimates, the system will generate up to 20 million kilowatt hours of electricity per year. The company said the initiative was among the largest of its kind.

The power generated by the solar panels will generate renewable energy credits, which Wal-Mart said it will keep.

The solar systems are designed to supply up to 30 percent of power for each store where the panels are located. The company said the systems will reduce greenhouse gas production by up to 11,000 tons per year.