SolarCity’s claim has been verified by Renewable Energy Test Center, while Panasonic’s by the Japanese National Institute of Advanced Industrial Science and Technology. We might have an “every radio station is the number 1 radio station” situation here.
The confusion might be due to SolarCity claiming the best “rooftop solar panel” and Panasonic talking about a “commercial-sized” solar module. Also it would be fair to mention that Panasonic is only talking about a “prototype module”, while SolarCity announced that it will start production at its 100 MW pilot plant in Fremont by the end of the month and they already confirmed a cost of about $0.55 per watt for 355 watts panels.
A few days after Panasonic’s announcement, SunPower came out with a blog post claiming its X-Series solar panel is the “most efficient solar panels commercially available today”. The X-Series with a verified 21.5% efficiency was indeed the most efficient panel before SolarCity’s announcement earlier this month of 22.04%.
SunPower’s X-Series still has a nameplate value of 21.5%, but it now claims that “in some cases [they] are finding that these panels are exceeding 22 percent efficiency, as verified by the U.S. Department of Energy’s National Renewable Energy Laboratory”.
Until all those products hit the market it will be difficult to declare a winner, but consumers should appreciate these competing announcements nonetheless. The price of solar modules has been falling over recent years, but efficiency has been stuck between 15 and 18 percent for residential panels for quite some time now. We might be witnessing early signs of an upcoming push toward the 20’s percentile of efficiency which will be great for distributed residential solar. The cost of installation will go down and consumers will be able to install more power on smaller roofs.