The ISO notifies utilities of electrical emergency alerts due to low electric reserves.
Utilities use the media to notify consumers throughout the state.
There are three stages of alert under the state's Electrical Emergency Plan. During a Stage I emergency, utility customers throughout the state are urged to voluntarily reduce their use of electricity. Stage I takes effect when the electric reserve margin, or backup generating capacity, in California drops to 5 percent above customer demand. If reserves dip to 3 percent, utilities will initiate Stage II of the plan and appeal for more stringent voluntary cutbacks. If reserves fall to 1.5 percent, utilities enter Stage III, implementing rotating power outages.