As high clouds slipped in front of the sun, executives from MillerCoors flipped the switch Thursday on the largest solar panel array of any brewery in the country.

When the sun is out — a pretty sure bet in Southern California — the 10-acre, 10,000-unit, fixed solar panels installed in three locations on the grounds of the Irwindale plant will generate enough energy to produce 7 million cases of beer per year.

The black solar panels, which are very similar to those affixed to rooftops and parking lots, will provide between 7 percent and 40 percent of the plant’s electrical energy, said Kim Marotta, MillerCoors director of sustainability.

Marotta, who flew out for the ceremony from Milwaukee, said the Irwindale site was chosen from among eight brewery plants because of its location. It’s the only MillerCoors facility in sunny Southern California.