When the Lights Go Out

Patterns in power outages that affect us all.

“power outage” by RubyT (driving far, far away to move) is licensed under CC BY-NC-ND 2.0

Infrastructure is an important topic right now with all the debates in Congress over how to spend over $4 Trillion. A key element in those discussions is what to do about the Nation’s aging electrical grid. This is a concern for everybody because, unlike most of the other elements of the infrastructure proposals, everybody uses electricity.

This article is an analysis of 1,652 power outages that occurred in the conterminous United States from 2000 to 2014. It summarizes patterns in where, when, and why power outages occurred.


Data for the locations of power outages is based on a U.S. Energy Information Administration (EIA) map for regions defined by the North American Electric Reliability Corporation (NERC). Boundaries for the regions change periodically so locations are approximate. Seven regions compiled from the EIA map are:

  • Northeast—New England, New York (ISNE, NYCW, NYUP, NPCC)
  • East—Mid-Atlantic States (PJME, PJM, ECAR, MAAC)
  • Southeast—Tennessee Valley, Mississippi Delta, Florida, (MISS, FRCC, SERC. SRCE, SPP)
  • Midwest—Ohio Valley (MAIN, RFC, PJMW, PJM, PJMC)
  • Central—Mississippi Valley, Great Plains (SPPC, SPPN, SPPS, MAPP, MRO, MISC, MISE, MISW)
  • Texas—most of Texas (ERCOT, TRE)
  • West—the Rockies and west (SRSG, CANO, CASO, BASN, RMRG, NWPP, WECC)

During 2000 to 2014, most power outages occurred in the Southeast, Midwest, and West. In the Southeast and West, however, the durations of the outages were comparatively short. In contrast, the average duration of outages in the Central part of the country was over five days, two-and-a-half times the National average. Most of those outages were weather-related.


Hundreds of specific causes of power outages were reported in the database. These causes were consolidated into six categories:

  • Deficiencies in supply, fuel deficiencies, inadequate electric resources, distribution disruptions.
  • Excessive demand, energy emergencies, voltage reductions, load sheds, public appeals.
  • Equipment malfunctions, failures, tripped breakers, faults, separations, islanding, system tests.
  • Weather, wind storms, snow/ice storms, hail, fog, dust storms, lightning, cold snaps, heat waves.
  • Events Not Related to Weather, wildfires, flooding, earthquakes.
  • Physical attacks, sabotage, vandalism, theft, cyberattacks.

As you might expect, by far most outages were attributed to weather. The one region where this was not true was the West. In the western half of the country, more outages were attributed to non-weather events, equipment failures, attacks, and supply issues than any other region. Wildfires were a notable cause of power outages in the West. Outages attributable to high energy demands were greatest in the Southeast. What did they do before air conditioning?


Power outages occur all the time, but there are some notable patterns in when they occur during a day, a particular season, and over the longer term.

 Times of Day

It might seem that power outages occur mostly during prime-time television viewing hours. That’s just a misperception. Power outages between 6 PM and 6 AM account for just 35% of all outages. Most outages begin in the afternoon and last an average of 39 hours.


It will probably come as no surprise that power outages tend to occur most frequently in summers and winters. That’s when demands for cooling and heating reach their peaks. For some reason, outages last longer during the fall and winter than they do during the spring and summer.


Number of Power Outages in the Conterminous U.S. from 2000 to 2014

The dataset only covered 13½ years, from 2010 to mid-2014, but one pattern is quite apparent. The number of power outages in the conterminous U.S. is increasing at an average rate of 16 events per year. This may be attributable in part to an aging infrastructure, weather anomalies, and disruptions in energy supplies. The most likely cause, however, is attacks, both physical and virtual. Improvements to the national electrical grid proposed in the Senate’s infrastructure bill and spending plan are needed as soon as possible to address these causes.


Most power outages last only a short time. 15% of outages last an hour or less. Half of outages last less than 14 hours. Only six power outages in the database lasted longer than a month, the longest being 131 days. That outage was caused by a suspected cyberattack beginning on June 21, 2013 at 8:31 AM involving ITC Transmission in Michigan and Iowa. The cyberattack turned out to be a false alarm.

Attacks can lead to longer-than-typical outages because they are unusual. Conventional resolution procedures are not always appropriate. Furthermore, the location of an attack is a crime scene. Not only does the outage have to be corrected but the perpetrators also have to be identified and apprehended. Cyberattacks in particular are challenging because the instigators may not be located anywhere near the power facility.

Other than attacks, the causes of outages that tend to have the longest durations are wildfires and supply interruptions. Wildfire-related outages are problematic because the fires have to be controlled before power can be restored. Supply-related outages are problematic because fuel sources are usually already committed and have to be purchased from other suppliers. These events can cause outages that last, on average, from one to three weeks. That’s a long time to go without heat.

So the next time your power goes out, imagine what it must have been like a hundred years ago before our national electrical grid was established. There was no looking forward to the end of a blackout, it never ended. Now we only have to put up with power losses for finite periods, though they may seem like an eternity. And if Congress decides to invest in our electrical infrastructure, maybe future outages will be fewer and shorter than they are now.

“Keeping warm with an oven or stove” by State Farm is licensed under CC BY 2.0

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