California’s grid operator is warning of possible rolling blackouts and calling on the state’s utilities to start cutting power to some customers. On late Friday, the California Independent System Operator declared a Stage 2 emergency for the first time since 2006, asking utilities across the state to curtail service to customers that had already agreed to disruptions when demand is high in return for incentive payments. The declaration means the grid manager is no longer able to meet demand without market intervention and shuttered power plants may be ordered back online.