USA Today: Nancy Arntson spent a year thinking about installing solar panels at her home. It wasn’t until her neighbors decided to take the plunge together — generating significant savings — that she made up her mind to do it. "It takes the right financial incentive to make it happen," Arntson said. The group of neighbors, called "Solarize Salem," is the latest in a wave of grass-roots efforts around the country to connect homeowners interested in solar power. The …