SolarCity, the company co-founded by Elon Musk, now produces the world's most efficient rooftop solar panels with a module efficiency of just over 22 percent. That bests the X-Series panels built by SunPower, which top out at around 21.5 percent. The results were confirmed by the Renewable Energy Test Center, a third party California photovoltaic testing company. SolarCity CEO Lyndon Rive told Fortune that the company is shooting for a cost of around 55 cents per watt. It plans to build the 360 watt panels its 1GW solar panel plant in Buffalo, New York, set to open next year.If 22 percent doesn't sound particularly great, you may be thinking of the (extremely expensive) panels used by NASA in space, which have nearly double that efficiency. However, the slight improvements made by SolarCity with its new panels will still have a big impact, bringing more power, less waste and a smaller footprint to consumers. The company said that a smaller pilot line is already producing the panels, which it will sell in select areas to start with. Once the main line is running, SolarCity will build enough of them to equip up to 200,000 homes per year.
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