At Walgreens, solar power is becoming so common that the chain changed its standard design template to more easily accommodate the equipment. “We literally will invest in solar in any state” if it makes sense economically, said Menno Enters, director of energy and sustainability for the drugstore chain.

Retailers are pursuing other forms of renewable energy as well.

Kohl’s, a department store chain, will have 150 solar locations by the end of this year, the company said. But it is also testing wind energy and plans to expand the number of electric vehicle charging stations at its stores.

Ikea has included a geothermal power system at a new store in Centennial, Colo.

Walmart, which has 150 solar installations and plans to have 1,000 by 2020, is also experimenting with wind. It has put small wind turbines atop the lamp posts in some of its store parking lots, and it has installed a giant one-megawatt wind turbine at a distribution center in Red Bluff, Calif. The chain, which has an aggressive goal of eventually deriving all of its energy from renewable sources, is also drawing power from fuel cells in some locations, said Kim Saylors-Laster, vice president of energy for the company.

Executives say part of the appeal of the solar systems is that big-box stores are exactly that: big boxes with plenty of roof space to put up their arrays to help cover heavy electrical needs for lighting, heating and cooling and, in some cases, refrigeration.

Many of the chains began with a few installations about five years ago but have picked up the pace in recent years as the price of equipment has plummeted. The average price of a finished commercial photovoltaic system, for example, dropped by almost 14 percent between the second quarter of 2011 and the second quarter of 2012, the report said.

In addition, new financing approaches — in which third-party companies offer to install systems for little or no money upfront and instead take fixed payments for the electricity generated over a long-term agreement — has made solar even more attractive. Although the cost savings from these arrangements are not as great as for residential customers, the agreements insulate the companies against fluctuations in electricity costs, said Lyndon Rive, the chief executive of SolarCity, which provides solar products and services, and counts Walmart among its commercial customers,