Andrew Seidman, INQUIRER STAFF WRITER BLACKWOOD One of the biggest solar energy providers in the country is expanding into South Jersey. SolarCity opened an operations center in Blackwood, Camden County, last month in a bid to tap into what the company says is a growing demand among middle-class homeowners for the technology. The San Mateo, Calif., company installs solar panels on south-facing sunny rooftops free of charge. Customers sign 20-year contracts, paying for the energy those systems provide. Photovoltaic solar cells convert sunlight directly into electricity. Solar is more competitive with traditional power sources in New Jersey because of the state's relatively high utility rates. The Blackwood operations center features an 8,500-square-foot warehouse where crews haul the panels and other raw materials onto trucks and take them to houses for installation. S olarCity, which has about 1,800 residential customers in the state, also has offices in Princeton and Cranbury Township, Middlesex County. Before launching operations in Blackwood, crews would drive hours to install panels in Cape May. Installations could take up to three days, said Lee Keshishian, East Coast regional vice president. Workers in Blackwood aim to get to job sites within 30 to 45 minutes to slash transportation costs and boost efficiency. Now a single crew can complete an installation in less than a day, operations manager Russ Pierson said. "Yes, we're a large national company," Keshishian said during a tour of the facility Friday. "But we're very much about being a local operation." SolarCity's chairman is Elon Musk, the entrepreneur behind such high-profile ventures as the Tesla electric car and the SpaceX rocket company. SolarCity was attracted to South Jersey because of its demographics and newer housing stock, Keshishian said, noting that modern houses are more suited to solar panels. Customers generally save 10 percent to 20 percent on their utility bills, he said. In New Jersey, the fastest-growing areas for rooftop solar have median incomes ranging from $30,000 to $40,000, according to an October report by the Center for American Progress, a liberal think tank in Washington. That trend tracks closely with other growth markets in California and Arizona, the study found.