What to Know About Rotating Outages

Rotating outages are used by grid operators as a last resort to prevent more widespread, longer-lasting outages under extreme circumstances.

What are rotating outages?

Sometimes called “rolling blackouts,” these utility-controlled service interruptions cycle through different areas to reduce overall energy use when demand exceeds the current supply. This can happen if power plants or transmission lines aren’t available during periods of high energy use, such as during extreme weather events.

Rotating outages can prevent far more devastating uncontrolled blackouts that can cascade through the regional grid, trip power plants and other resources offline and take days or even weeks to restore. By intentionally rotating outages from one area to another, grid operators seek to minimize the impact on any one area.  The outage duration is usually 30-60 minutes and will go on as long as necessary to address the emergency.

Could something like that ever happen here?

It’s possible, especially if the entire Western regional grid is under stress from extreme heat. This is why we take a regional approach to monitoring grid operations. We track weather, wholesale market prices and unit outages across Arizona, New Mexico, Nevada and California to help ensure that we have adequate resources to meet customer demand.

TEP works around the clock all year long to avoid energy shortfalls. We review usage trends and weather forecasts to anticipate our customers’ energy use and then secure more than enough resources to cover those projected needs. If problems arise, we can shore up our own resources with energy purchased by the hour on the wholesale energy market.

What could cause rotating outages here?

A combination of factors can create a need for rotating outages, including:

  • The unavailability of power plants, substations or transmission lines
  • Extreme weather that drives energy use higher than expected
  • Natural disasters (wildfires, floods, solar flares)

Our regional energy grid can overcome some of these problems, but the accumulation of issues under extreme circumstances can force grid operators to rapidly reduce load in order to maintain stable voltage. Power plants and transmission lines can trip offline if system voltage drops too low, compounding energy shortages and leading to uncontrolled outages.

How does TEP decide which customers will be impacted?

If rotating outages become necessary, TEP seeks to limit them to areas of our local energy grid that are under the most stress. If possible, we try to avoid shutting off service multiple times in the same area. We avoid interrupting service to critical customers, such as hospitals or law enforcement agencies, unless doing so is unavoidable to maintain system stability.

Can customers help TEP avoid rotating outages?

If possible, TEP will issue a public appeal for energy conservation before rotating outages become necessary. If that happens, please consider adjusting your thermostat and making other changes that could help reduce our community’s energy use. We also may ask industrial users to pare back their energy use and request that local governments implement their plans for energy reduction.

Over the long term, customers can help make rotating outages even more unlikely by reducing energy consumption during peak usage periods, including from 3 p.m. to 7 p.m. during the summer months. Click here for tips on how you can reduce your electricity demands during those hours of peak usage and why it’s important.