No single factor caused California’s rolling blackouts during the August heat storm, but mishandling natural gas-fired generation resources was cited as a reason as the grid operator used rotating outages during two days of peak power loads.

The California Independent System Operator (CAISO), California Energy Commission and the California Public Utilities Commission on Tuesday issued a preliminary root cause analysis of the Aug. 14-15 outages. Gov. Gavin Newsom has requested “immediate action” to minimize use of the blackouts.

Among the causes cited was that natural gas resources bid in 300 MW less than the state’s fleet of gas-fired generator resource adequacy (RA) requirements. There was a 1,000 MW difference between the RA needs and the bids for resources, “largely...