Solar panels can create the electricity needed to power your business, but there's one thing they won't do: Clean themselves.

For that, local companies are hiring ProSolarClean, a Glen Ellen business whose owners say that dirty solar panels can't generate the maximum amount of electricity.

"You are missing a lot of energy," said Jan Klimes, one of the three partners.

The 2-year-old company has cleaned panels for the San Francisco Public Utilities Commission, the North Marin Water District and several North Bay wineries.

"It makes a big difference," said Greg van Dalen, facilities manager at Ravenswood Winery near Sonoma. "We gained about 15 percent production just from cleaning."

Klimes and partners Karel Jetleb and Richard Nezval started ProSolar after concluding that many companies install solar power systems, but fewer clean the panels that transform sunlight into electricity.

Klimes first sold solar energy systems in his native Czech Republic after working in a California nursery from 2000 to 2008.

Europe's frequent rains greatly help clean the panels, he said. For example, solar energy systems may need just one cleaning a year in Germany. But in California, they may require two to three cleanings a year.

In 2012, Klimes returned to the U.S. and enrolled in a school for solar designers. He became convinced that there was a demand for a solar panel cleaner, so he helped found ProSolar. The company relies on a German-made cleaning system that uses special brushes, deionized water and no chemicals.

At Ravenswood, the winery's maintenance staff cleans about half of the 2,000 solar panels, van Dalen said. But he chose to have ProSolar clean the other half, where the panels are a little more difficult for his crew to reach.

He plans to have ProSolar clean those panels three times in spring and summer.

"They worked safely and they got the panels exceptionally clean," van Dalen said.

At Community Market in Santa Rosa, manager Melissa Minton said the market's 300 panels previously were cleaned by a company that used a garden hose and a squeegee. She hired ProSolar this spring after learning that deionized water will better clean the panels.

"We want to get the most for our money," Minton said.

ProSolar's biggest project to date has been at Sonoma Mountain Village in Rohnert Park, where its crew cleaned nearly 11,000 solar modules.

The company, which uses seasonal workers to assist the three partners, also cleans home solar systems. Competitors in the residential market include North Coast Solar Clean of Sebastopol.

Many homeowners assume they can install a solar power system and then forget about it, said David Moore, North Coast's owner. "Well, that's not really true ... Somebody's got to wash them."

Moore said he also uses a system with deionized water that leaves no water spots.

Both companies said most customers see their power output increase 10 to 15 percent after cleaning.

With dirty panels, said Klimes, "it's still money being left on the roof."