Word Document


Sheri Inouye

May 11, 2001







Q1: What is the Rotating Outage Program?

A1: The Rotating Outage Program, which was established by the California Public Utilities Commission (CPUC) in 1980, is a way to systematically and fairly address the need for forced reductions in electric use by cutting power to customers when the electrical system is close to collapse.

Q2: What are rotating outage blocks and how are they determined?

A2: When the Independent System Operator (ISO) determines that reductions are necessary to prevent collapse of the electric system, it notifies the utilities and requires them to cut electricity use ("drop load" is the industry term). This usually occurs during a Stage 3 electrical emergency. In response, the utilities cut off power to the number of rotating outage blocks necessary to provide the relief requested by the ISO. Rotating outage blocks (and sub-blocks) represent about equal amounts (e.g., 100 MW) of electrical load and consist of geographically dispersed distribution circuits, each one numbered. Circuits with essential-use customers, as well as all the customers served by that circuit, are exempt from rotating outages. With a few technical exceptions, other customers are included in rotating outage blocks and have equal chances of being curtailed, that is, having their power shut off. In addition to essential-use customers, participants in the Optional Binding Mandatory Curtailment (OBMC) program are exempt from rotating outages. OBMC participants must reduce the load on their circuit by up to 15 percent for the entire period of every rotating outage. Customers enrolled in interruptible programs are subject to rotating outages and receive no special preferences during rotating outages

Q3: What is the relationship between the Interruptible Load Programs and rotating outage blocks?

A3: The Interruptible Load programs are utility programs in which large users agree voluntarily to reduce their electric usage on demand in return for a monetary payment or bill discount. Load reductions are usually called during a Stage 2 electrical emergency. If sufficient reductions are obtained from interruptible programs, forced cut-offs of power to blocks may not be required.

Q4: Who and what determines which blocks are to be interrupted?

A4: When operating reserves of electricity fall below about 1.5-2.0 percent, the ISO calls a Stage 3 electrical emergency and orders the utilities to reduce electrical use by a certain amount. The utilities then curtail (black out) sufficient predetermined blocks. After a specific period of time (generally about 1 to 1-1/2 hours), power is returned to the first block or blocks and the next block is curtailed. After being curtailed, the block goes to the end of the rotation and will be the last to be curtailed in future emergencies. The actual makeup of the rotating blocks is established by the utilities in their emergency plans, subject to Commission review.

Q5: Is the utility liable for damage due to blackouts?

A5: No. When a utility implements its Rotating Outage Plan, it is not liable for any damage to the customer's electrical equipment or impacts on the customer or his property. (As discussed in the following answers, customers should be prepared.)

Q6: Who is exempt from rolling blackouts?

A6: Essential-use customers, as determined by the Commission, and any other users on the same circuits, are exempt. Essential-use customers include government and other agencies providing essential fire, police and prison services, hospitals, communication and broadcasting facilities, and certain others.

Q7: What is the process for notification of an imminent blackout?

A7: Electrical outages can occur at any time without warning for several reasons (e.g., accidents such as a car hitting a power pole, shortages, natural disasters, and equipment failure). Therefore, everybody should be prepared. An ISO order for curtailment may require shut-off of power in 10 minutes or less. When notified by the ISO, the utilities will notify life support and critical care customers, as circumstances (and time) permit. Utilities also notify large customers, having a demand of 300 kW or more, and other customers who can demonstrate major economic damage or clear and imminent danger to health or safety, by telephone and/or other means. For all other customers, warnings of imminent blackouts, the number of the next block to be blacked out, or other relevant information are given by mass media, and no individual notification is generally provided. The utilities that were not already doing so were directed to include rotating outage blocks on customer bills beginning with bills issued no later than June 1, 2001. However, customers may at times be temporarily switched to other rotating blocks for operational or maintenance reasons.

How do customers on life support equipment and critical care customers get notified?

A8: The utilities will notify customers on life support equipment and critical care customers of imminent rotating outages by automated or personal phone calls, as time allows.


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