Big-box retailers are increasingly adding solar panels and wind turbines to sprawling stores to offset rising electricity costs and groom a "green" image. Last week, Wal-Mart Stores announced it will add wind power to 360 Texas outlets. The company aims to power all stores with renewables eventually. So far, the retailer counting the largest amount of photovoltaics is Wisconsin-based Kohl's. Whole Foods is likely the first big name to add solar panels, starting in 2002 in Berkeley, Calif. In the latest sign of government support for such efforts, Massachusetts Gov. Deval Patrick called last week for all new malls and massive retailers to install solar panels. That state's rebates of up to 40 percent for photovoltaic installations are among the most attractive in the country for retailers eyeing regional and federal discounts for installing cleaner forms of energy.