In recent months, chains including Wal-Mart Stores, Kohl’s, Safeway and Whole Foods Market have installed solar panels on roofs of their stores to generate electricity on a large scale. One reason they are racing is to beat a Dec. 31 deadline to gain tax advantages for these projects.

So far, most chains have outfitted fewer than 10 percent of their stores. Over the long run, assuming Congress renews a favorable tax provision and more states offer incentives, the chains promise a solar construction program that would ultimately put panels atop almost every big store in the country.

If Wal-Mart eventually covered the roofs of all its Sam’s Club and Wal-Mart locations with solar panels, figures from the company show that the resulting solar acreage would roughly equal the size of Manhattan, an island of 23 square miles.

[Read](http://www.nytimes.com/2008/08/11/business/11solar.html?_r=2&ref=todayspaper&oref=slogin&oref=slogin “Read the Article”) (New York Times)