Last year, a reader wrote in to Grist's advice column with a question: Why doesn't every roof have solar panels? A report released this week by the nonprofit Environment America and the research firm Frontier Group poses a followup question: At the very least, why doesn't every big box store have rooftop solar?
The amount of space available on the rooftops of Walmarts, Targets, Home Depots, Costcos, and other large stores and shopping malls in the continental U.S. is staggering. Environment America estimates that it amounts to 7.2 billion square feet, or about the size of El Paso, Texas. Even tiny little Rhode Island has 279 stores that span at least 25,000 square feet each.
