A rooftop solar array at a Kohl’s store

When shoppers line up for midnight Black Friday sales outside Kohl’s department stores this week, the lights they stand under will very likely be powered by the wind.

Kohl’s, based in Menomonee Falls, Wisconsin, was recognized by the U.S. Environmental Protection Agency this month as one of its Green Power Partners of the Year.

The retailer quietly ramped up its renewable-energy purchasing in recent years, from approximately 850 million kilowatt-hours in 2009 to more than 1.3 billion kWh in 2010 — enough to meet 100 percent of its purchased electricity needs.

Among retailers, it’s now the largest buyer of renewable power, beating out companies like Walmart and Whole Foods that put a lot more marketing muscle into their green image. In its rankings, the EPA includes on-site generation such as rooftop solar, as well as renewable energy credit purchases and participation in utility wind and solar programs.

The company’s stores also host more solar arrays than any other retail chain. More than 100 of its 1,100-plus locations generate 20 to 40 percent of their power from on-site solar, which collectively generating around 15 million kWh of power annually.

Like Walmart, Kohl’s is also working with its merchandise suppliers to track sustainability measures. More than 300 suppliers submit quarterly surveys on energy-efficiency and renewable power use.

The company’s sustainability website has an interactive map that lets you look up the location of its LEED-certified, Energy Star-labeled, and solar powered locations. The map below shows states with solar installations: