For years, SolarCity Corp (NASDAQ:SCTY) investors were concerned how the company would perform after the federal tax credit expires. The San Mateo-based residential solar installer has now developed the "world's most efficient" solar panel that would help it keep solar cost competitive even after the tax credit expires next year. SolarCity said in a blog post that its new panel could generate 30% to 40% more power per square foot area, while costing less than other PV modules in the market. SolarCity's new panel boasts of 22% efficiency SolarCity chairman Elon Musk said the new panel had an efficiency of 22%. Most commercially available solar modules have... More