Statewide Electric Grid Emergengy

Rotating Blackouts

If unusually high demand for electricity or unexpected loss of generation units causes Electric Reliability Council of Texas (ERCOT) generation reserves to drop below target levels, ERCOT initiates a three-step Energy Emergency Alert (EEA) process.

During that process, if generation reserves drop to critical levels and after all other measures have been employed, ERCOT will order utilities statewide to initiate rotating blackouts. This step is only taken by ERCOT to prevent the statewide electric grid from going black. This step can be initiated very quickly, depending on the speed of events.

When statewide rolling blackouts are ordered, utilities must turn off customers on a rotating basis to reduce electric demand by an assigned amount. That assignment can be increased very quickly until the statewide electric grid is back in balance between the electricity being demanded statewide and the generation available to meet that demand.

How Rotating Blackouts Work

Austin Energy currently has identified 71 circuits available to meet rotating blackout requirements. Once ordered to initiate rotating blackouts, Austin Energy staff identifies a group of circuits that add up to the assigned (load shed) requirement. Circuits are selected from each section of the community, north-east-south-and west. The circuits are turned off for 10-15 minutes and the process is repeated with another group of diverse circuits, with power restored to the first group.

The Austin Energy Distribution Circuits Map shows all Austin Energy circuits. The configuration of circuits can change weekly due to maintenance, system upgrades or expansions or re-balancing the amount of demand (load) a circuit serves. For this reason, a map today may look different from the map next week. To keep the map as current as practical, it is updated quarterly.

View the Austin Energy Distribution Circuits Map (pdf)

Color Coding of the Austin Energy Distribution Circuits Map

• Green circuits available for rotating blackouts.
• Light blue (circuits serving large companies) and orange (circuits serving the downtown) not available for rotating blackouts. If one of these circuits is turned off -- another circuit immediately keeps power flowing to customers. Disabling this automatic backup requires sending a crew to make physical adjustments, this is not practical in a fast paced emergency. Also, the amount of power flowing to these entities does not lend itself to quick
  on-off rotations.
• Tan (critical loads) circuits power critical public health and safety resources such as hospitals, airport, water and wastewater plants, headquarters of police, fire EMS, DPS, cell and communications towers and more. These circuits are not available for rotating blackouts.
• Purple circuits are 100 plus circuits outfitted with special equipment. If the frequency of the statewide electric grid drops to a certain level, these circuits begin to automatically turn off as a last defense to a complete blackout of the statewide electric grid. Every community under ERCOT has a group of these specially outfitted circuits, that act automatically in tandem.