Innovation amid a raucous rooftop solar squabble

The explosive expansion of U.S. residential rooftop solar installations- which increased by 51 percent last year-threatens utilities' traditional role as electricity suppliers. The resulting backlash has been most intense in sun-bleached Arizona, which is second only to California in installed solar capacity. The battle has the potential to blunt the state's solar growth, but there are signs that it could also inspire grid-friendly technologies that expand solar's role.