Capt. Tracey Stuart said it was the 17th theft of solar panels in Napa County since January 2008. All but four have been stolen from wineries, Stuart said.
Some wineries are erecting fences but the thieves cut through them, Stuart said.
The Rutherford winery did not want to be identified, fearing it will be targeted again, she said.
The majority of the thefts happen late at night or early in the morning at rural locations, Stuart said.
Those with solar panels are asked to secure them and information on how to do so is available by calling (707) 253-4280, the sheriff's office said.
Anyone with information about the thefts is asked to call (707) 253-4591. Anyone witnessing a theft is asked to call (707) 253-4551.