According to CNBC:

In recent months, chains including Wal-Mart Stores 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.

It’s about time!