Twenty home and business owners have signed up for Solarize Salem and Swampscott, a joint program of the two communities under Solarize Massachusetts that will run through June. Run by the Massachusetts Clean Energy Center and the state Department of Energy Resources, the program promotes the use of solar power at residential and business properties using a single vendor (RGS Energy) and benefiting from community marketing and economies of scale. In simple terms, the price goes down as the number of customers goes up, said Sydney Pierce, “solar coach” for Swampscott. “For people who want to solarize but don’t know when or where to start, this is a good time to move ahead,” she said. She noted that Swampscott and Salem are already up to Tier 4 of five tiers (based on kilowatts), with each tier recognizing more savings. “We’re thrilled,” she said, adding that most consumers tend to wait until late in the project to join. “To already be at Tier 4 at this point in the process is amazing.” For more information, e-mail SolarizeBigBlue@gmail.com or SolarizeSalem@gmail.com.