Although residential solar customers want systems with the highest power ratings for maximum utility cost savings, aesthetics still reign supreme when it comes to solar panel choice. If even a sliver of an array will be seen by neighbors, homeowners will usually pick all-black modules for a sleek, finished system.
There aren’t many differences between “traditional” solar panels and their all-black counterparts. Traditional panels use white backsheets and silver frames, while all-black modules use — you guessed it — black backsheets and black frames. They’re manufactured the same way through the same processes, except black adhesives may be used around junction boxes and other electronics on all-black modules.
The major difference between the two is their efficiency ratings. All-black modules run a bit hotter and offer fewer opportunities for reflected light absorption, so their efficiencies are slightly lower.
“When white backsheets are used, the empty spaces or gaps between and around the solar cells provide a reflection of the unused light and increase the likelihood of ‘light trapping,’ resulting in an increased generation of photocurrent,” said Geoff Atkins, executive advisor of North American panel manufacturer Silfab Solar. “All-black modules have a more aesthetically pleasing look but lose the benefit of reflection and light trapping, resulting in a lower photocurrent — up to 3% less than a white-backsheet module. Three percent less current means about 0.5% lower absolute efficiency.”
To even out this major difference, companies like Silfab will use higher efficiency solar cells in its all-black modules. The company also uses a back-contact design — wherein all busbars and electrical connections are moved to the back of the solar cells — along with a flexible, conductive backsheet to more effectively spread the heat produced by a module. This lowers the nominal operating cell temperature of Silfab modules, providing a higher module efficiency.
But a 0.5% efficiency loss isn’t especially noticeable to the average residential customer, so often these extensive production efforts aren’t made on all-black modules.
When Silicon Valley solar panel startup Aptos Solar Technology began making panels in 2019, CEO and co-founder Frank Pham knew his company’s role as a newcomer in the industry was to stick to the mainstream — and that meant providing both white- and black-backsheet modules. Aptos wants to be competitive and innovative, but Pham said he can’t ignore customer desire for attractive systems.
“The biggest advantage of all-black vs. white is the aesthetic. It’s exactly why you would pay Tesla [more] for an electric car over a Chevy Bolt. It’s the same electric car performance, but it’s about aesthetics. It’s not about performance,” he said. “We know that white backsheets will out-perform the black backsheets, but the key is to make sure the aesthetic is good while maintaining a very good panel output.”
Aptos Solar’s white- and black-backsheet modules are identical in specs, except for that less-than-0.5% efficiency difference. Pham said that difference is moot when residential rooftop systems use microinverters. If the microinverter is power-rated for less than what the module will produce, it doesn’t matter if the back of the module is black or white — might as well go with the more aesthetically pleasing option.
“If you’re going to clip 30% of the power anyway and you’re running a silver frame, you’re just wasting it,” Pham said. “You throw on something that is ugly? You’re just wasting power and throwing ugliness up on the roof.”
Customer demand reinforces the all-black trend. Many residential solar installation companies across the country now offer all-black modules as standard. Washington-based Northwest Electric and Solar works on both residential and commercial projects but keeps things simple for homeowners.
“We started offering all-black modules years ago for customers that had aesthetic concerns, and now they’re part of our standard offerings,” said Ian Robinson, energy program manager. “We pitch ourselves as a company that installs premium products and refuses to sacrifice on quality. Part of that is offering the best-looking modules possible. For that reason, we offer Solaria’s all-black modules to all our customers.”
Robinson said Northwest Electric and Solar will finish the project with black rails or rail-less mounting systems for the most visually pleasing array. But Pham with Aptos said all the major racking providers look good with all-black modules, as long as installers take time to finish the system in an attractive way.
“If you take special care, the installation will look just as good as any other,” Pham said.