Crews restored power to West Orange Elementary around 11 a.m. The power outage threatened to cancel classes.
Power was lost overnight as someone cut the main lines to the school, tripping the school's alarm system.
"Security responded about 12 minutes later and saw a subject running from school grounds," said Mike Pollok with the Orange Unified School District.
The thief got away, making off with 15 circuit breakers and resulting in an estimated loss of $750 plus damages to the school. It is possible the suspect was also going after the copper wiring in the air conditioning units.
"It certainly would be speculation as to whether he was going to steal the copper wire or not, there's a lot of possibilities for what he could have taken," said Orange Police Sgt. Fred Lopez. "It will be unknown until we apprehend him."
Three copper thefts totaling $30,000 occurred last month at three Fullerton schools. In those cases, thieves targeted the copper in the air conditioning units. Copper has a significant value at state recycling centers, and police say they have seen a rise in copper thefts in recent years.
It was unclear if the theft in Orange was related to the three incidents in Fullerton.
There is no suspect description. Anybody with information on the incident should call police.