The sun is a virtually endless supply of energy that goes mostly untapped. The solar panels you see covering the roofs of an increasing number of homes and businesses capture some of that energy, at least during the daytime and when there isn’t extensive cloud cover, but, by most standards, they are incredibly inefficient.

See also: How solar panels could capture a lot more sunlight on slanted roofs

Experts say the average solar cell panel can convert 14-to-20% of the energy it collects into usable electricity. By photosynthesis standards — a plant is 5% efficient — that's not bad, but humans believe solar panels should do better.

On Friday in New York City's Times Square, SolarCity, the nation’s largest installer of residential solar panels, and company chairman Elon Musk introduced what they claim is the world’s most efficient rooftop solar panel, achieving a peak efficiency of 22.04%.

SolarCity said the rating was verified by the Renewable Energy Test Center, a third-party certification testing provider for photovoltaic and renewable energy based in Fremont, California.

The panels are the same size as traditional panels, but, according to SolarCity, produce 30-to-40% more power. They also claim that the panels perform better than competing products in high temperatures.

Peter Rive, SolarCity's co-founder and CTO, told Mashable in an interview that the new panels are sufficiently cheap to produce that they will allow the company to continue to make money off of them even if government policies to provide tax breaks for panel installation expire.

“That’s been the singular focus of the company… to continue to get the costs down,” Rive said.

“I’m really excited about this… it’s the best solar panel on the planet and it empowers us from 2017 and beyond to control our own destiny,” he said.

SolarCity’s efficiency leap, however, may not be that big when compared to the current state of the art.

Solar energy expert John Farrell, who serves as Director of the Democratic Energy Program for The Institute for Local Self-Reliance told Mashable that typical solar panel efficiency is, at 18%-to-22%, actually in the same range as SolarCity’s new panel.

“In the lab they get to 40%,” said Farrell, but that’s with special materials that would likely jack up the cost of solar panels by 50%. Out in the field, companies like SolarCity must balance efficiency with cost.

When I asked Farrell about the increased power output he said, “That sounds like a lot. Not sure what they would be comparing it to.” If SolarCity’s current panel tech had a peak efficiency of, say, 16%, a 37% jump to over 22% could account for the difference.

Farrell does agree that heat management is an issue worth tackling. With solar energy, the very thing that lets these panels produce energy is also the thing that overheats them.

“In Minnesota, we have less sun, but that means the panels can work better here and be more efficient for the sunlight we have because it’s colder. So I’m not surprised that’s one of the things they work on,” said Farrell.

Are SolarCity’s new panels a true solar energy breakthrough? As far as Farrell is concerned, dramatically better solar panels is not the story, “I think the big story is SolarCity Installed one-third of all panels on residential property in the U.S. in the last year, so whatever they’ve done will get to a lot of customers.”

Still, 22% efficiency is nothing to sneeze at, especially wen you consider that, unlike traditional energy sources, you do not pay for the fuel — the sun — you put into solar energy.

When the SolarCity 1 gigawatt factory in Buffalo reaches full capacity next year, SolarCity said it plans to produce as many 10,000 solar panels a day.

The company previously acquired solar panel manufacturer Silevo to help fuel growth, but the decision to build panels at its own factory from the ground up comes from a different place.

Musk explained that when SolarCity looked at their third-party panel manufacturers, "They were happy to make a standard efficiency 15% panel year-over-year that looked not that great. So we thought we had to make our own panels," said Musk on Friday, adding, "I like counter-intuitive moves. I thought people would think, at the time, 'Wow, that’s stupid,'" which made him think, "That’s probably a good idea."

The company will continue to use external suppliers, but expects the 1 gigawatt factory to spur innovation. "We can say, you better match what our plant is doing," said Musk.

Andrew Freedman contributed reporting for this story.