Retailers are typically obsessed with what to put under their roofs, not on them. Yet the nation's biggest store chains are coming to see...

Share story

Retailers are typically obsessed with what to put under their roofs, not on them. Yet the nation’s biggest store chains are coming to see their immense, flat roofs as an untapped resource.

In recent months, chains including Wal-Mart, Kohl’s, Safeway and Whole Foods Market have installed solar panels on store roofs to generate electricity on a large scale.

One reason is that they are racing 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.

The trend, while not new, is accelerating as the retailers seize a chance to bolster their environmental credentials by cutting back on their use of electricity from coal.

“It’s very clear that green energy is now front and center in the minds of the business sector,” said Daniel Kammen, an energy expert at the University of California, Berkeley. “Not only will you see panels on the roofs of your local stores, but I suspect very soon retailers will have stickers in their windows saying, ‘This is a green energy store.’ “

In the coming months, 85 Kohl’s stores will get solar panels, while 43 already have them. Macy’s, which has solar panels atop 18 stores, plans to install them on 40 more by the end of this year. Safeway aims to put panels atop 23 stores.

And other chains, including Whole Foods Market, BJ’s Wholesale Club and Kent-based REI are planning projects of their own.

Wal-Mart, the nation’s largest retailer, has 17 stores and distribution centers with solar panels in operation or in the testing phase. It plans to add them soon to five more stores.

The chain is also considering a far larger program that would put panels and other renewable technologies at hundreds of stores.

Analysts are not sure how much power the rooftop projects could ultimately produce, but they say it could be enough to help shave total electricity demand. In many communities, stores are among the biggest energy users.

Depending on location and weather, the solar panels generate 10 to 40 percent of the power a store needs.

Booming demand has driven up the price of solar panels, and analysts say it costs far more to generate electricity from solar energy than from coal.

Coal generation costs about 6 cents for a kilowatt hour, enough electricity to run a hair dryer for an hour. Natural-gas generation costs about 9 cents a kilowatt hour, said Reese Tisdale, a senior analyst with the consulting firm Emerging Energy Research.

In comparison, “best case” for power from solar panels is about 25 to 30 cents a kilowatt hour, he said.

But retailers believe that they can achieve economies of scale.

With coal and electricity prices rising, they also bet solar power will become more competitive, especially if new policies addressing global warming limit the emissions from coal plants.