Everybody seems to blame the weather when there is a power blackout. Even grid operators.
But on Monday, the state's electricity grid operator said a March 9 blackout that affected 70,000 Southern Californians actually was caused by its own employees, who simply failed to increase output as demand surged amid record heat.
At the time, the California Independent System Operator indicated that the trouble wasn't caused by operator problems or market manipulation but by too many people using their air conditioners at one time.
Southern California Edison Co., a unit of Rosemead-based Edison International, was ordered by Cal-ISO to cut electricity to help relieve the pressure on a key transmission line.
Cal-ISO said Monday that the blackout was an isolated incident and didn't mean there would be summer shortages.
Several employees who failed to respond to ISO orders were disciplined, and new training programs were put into place, spokeswoman Stephanie McCorkle said, declining to be more specific.
Bloomberg News was used in compiling this report.