SolarCity says it now has the most efficient rooftop solar panel in the world, with a measured efficiency of more than 22%.
The company said that the photovoltaic (PV) module, whose performance was tested by the independent Renewable Energy Test Center, will go into production this month at a California pilot facility, but most of the modules will be produced at SolarCity’s huge new factory in Buffalo, N.Y. Production should reach between 9000 and 10,000 modules per day when the facility is running at full capacity sometime in 2017.
SolarCity is the largest residential PV installer in the country and acquired PV manufacturer Silevo, which developed the technology for the new PV module last year. SolarCity said in a press release that the new modules are the same size as standard ones but produce between 30% and 40% more power. They also perform better than other modules at high temperatures, allowing more energy production annually than conventional panels.
Claims of supremacy in the battle for high efficiency, however, are best taken with a grain of salt, or at least a close eye to the fine print. Although the new SolarCity modules are at or near the high end of what’s available commercially for residential applications, SolarCity rival SunPower already produces a module with an efficiency of 22.4%, which is listed by the National Renewable Energy Laboratory (NREL) as the most efficient module of its type. In addition, a day after the SolarCity announcement Panasonic said it had a module ready for mass production with an efficiency of 22.5%, according to PV Magazine.
More complicated and more expensive types of PV cells have much higher efficiencies. A chart published by NREL shows that the best photovoltaic cells have an efficiency of 46%–but you won’t find them in commercially made residential PV systems. “The 40% cells are a very niche market,” said Keith Emery, a group manager and principal engineer in NREL’s solar performance group. “Right now, the 20% to 22% silicon modules are at the high end of what’s commercially available for residential use.”
“If you have enough caveats, you can make almost anything a record,” he said of SolarCity’s claim. “It’s not necessarily a bogus claim. It’s just a little misleading, that’s all.”
Still, Emery was enthused by the announcement. “I regard it with excitement because it means there’s another player on a high efficiency end of the photovoltaic business,” he said. “One of the economics of these things is the higher the efficiency the lower the cost of energy. If they are still selling it at X dollars a watt, the higher efficiency system will have a lower cost of energy. The name of the game here is not to add to the dollars per watt at all and just raise the efficiency.”
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SolarCity claims its new solar panel is more than 22% efficient, making it the most efficient rooftop panel in the world.
