There are a lot of Americans who would love to get their energy from solar, but can't. They live in apartments and condos and don't own their rooftop. Or they do own a home or business, but really like the old oak tree that shades their roof. The National Renewable Energy Laboratory (NREL) estimated that 75 percent of American residential buildings have physical restrictions to going solar. Other building owners may have a suitable roof but for a variety of reasons may not want to commit to having a solar system installed on their own property. By limiting ourselves to the traditional "panels on your roof" approach to PV, we are leaving a tremendous amount of solar potential on the table.