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Rotational Or Rolling Blackouts

Electricity is becoming an increasingly important part of our daily lives. We have become dependent on electricity to provide us with uninterrupted light and power to our homes and offices, run our air conditioners and microwaves, and keep our favorite television programs on the air. Along with providing security in our communities and computer services in our businesses, we have developed a growing dependence on electricity. That is why when we experience a "power outage," that is, when "the lights go out," we are often caught off-guard and unable to continue with our regular activities.

To understand the situation facing California, there are three terms that need to be defined- blackouts, brownouts, and rotational outages or "rolling blackouts." A rotational outage or "rolling blackout" is when the utility company shuts off the power to an area, turns it back on, and then shuts the power off in a different area. The power outage typically lasts 60 to 90 minutes.

A brownout is when the electrical current flowing to your home or office is temporarily reduced (an average household can barely notice the difference). You may notice that the lights may slightly dim temporarily. These power reductions can be uncontrolled and controlled.

An uncontrolled electrical power outage occurs when your power supply is disrupted without warning. These are often caused by accidents (such as a car knocking down a power pole); weather conditions such as storms, heavy rains or high winds; or extended use of electricity that unexpectantly overloads electrical utility companies.

A controlled energy outage such as a "rolling blackout" is an organized and planned outage that typically occurs between the hours of 3 to 7 p.m. during peak times when demand for electricity begins to exceed the local utility's available supply. These controlled or planned blackouts help prevent "uncontrolled" electrical power outages during the peak periods, which assures your electricity supply remains continuous and with minimal interruptions.

To protect the electricity system, the State's Electrical Emergency Plan is implemented as peak electrical power demands increase the possibility of potential power shortages.

The plan directs the California Independent System Operator (the nonprofit agency that is in charge of 75 percent of the state's electricity supply) to issue public alerts, advisories and energy curtailments issued in the form of three stages of emergencies.

  1. When electricity reserves fall below 7 percent, Stage One is initiated to advise the public of potential power shortages and to ask all customers to conserve electricity to ensure there will be enough power to meet the peak demand.
  2. A Stage Two is initiated when reserves drop below 5 percent. Commercial customers who have signed up to voluntarily curtail power during high demand days are asked to do so.
  3. When electricity reserves of 1 and 1/2 percent is unavoidable, a Stage Three is initiated. This includes "rotational blackouts," and involuntary curtailment of service to customers.
logo of California Independent System Operation with link to their website

Being prepared for an electrical power outage will allow you to continue most of your regular activities comfortably without interruption and until the power is restored.