Wal-Mart, with 4,522 stores in the U.S., expects to have 1,000 solar-powered locations by 2020, Marty Gilbert, director of energy at the Bentonville, Arkansas-based company, said in an interview. The retailer gets about 4 percent of its power from renewable sources and plans to install another 100 solar systems by the end of 2012, demonstrating that renewable energy is economically viable to businesses.

“We are trying to show folks that you can not only pursue these sustainability initiatives, they also make business sense,” he said.

The company expects its use of renewable power to drive down prices, he said.

“The more we get involved and commit to volume, the more the prices come down for the technology,” he said. “Prices for solar panels, fuel cells, wind turbines to some degree, they are all approaching grid parity.”

Economic Sense

The company installed its first five solar projects in 2008. It’s installing panels in markets where utility rates are higher, such as California, Hawaii, Puerto Rico, Ohio and Connecticut, said Gilbert. Each system must add to the bottom line for the individual store.

“The only projects that we were doing are the ones that economically make sense at the store level.”

Wal-Mart has 26 fuel-cell projects and six projects. A 1.1- megawatt wind turbine at a store in Red Bluff, California, will be operational within a month, said Gilbert.

“Wall Street was watching to see if this was a public relations game and we would be passing the cost on to our customers, said Gilbert. ‘‘It’s not done on a portfolio basis, it’s every store analyzed individually.”

Other large companies are also installing U.S. solar projects. Apple Inc. is building a 20-megawatt solar farm and a 5-megawatt fuel-cell system to power a data center in North Carolina.

Ikea has solar projects at 26 U.S. sites and is planning to install 13 more, with total capacity of 38 megawatts.