SolarCity Corp, the largest installer of residential solar panels in the United States, reported a smaller-than-expected quarterly loss, citing “unprecedented demand.” The company, backed by Tesla Motors Inc founder Elon Musk, said it added more than 30,000 customers in the second quarter ended June 30, compared with 8,559 a year earlier. SolarCity’s shares were up 5.3 percent at $79.63 in extended trading on Thursday. The San Mateo, California-based company said it deployed 107 megawatts (MW) of solar panels in the quarter, in line with its forecast of 105-110 MW. “We are well on our way to achieve our million customer goal in 2018,” SolarCity Chief Executive Lyndon Rive said on earnings conference call.