Large Blackouts in North America: Historical Trends and Policy Implications

Paul Hines, Jay Apt, and Sarosh Talukdar , Carnegie Mellon Electricity Industry Center

Using data from the North American Electric Reliability Council (NERC) for 1984-2006, we find that the frequency of large blackouts in the United States has not decreased over time, that there is a statistically significant increase in blackout frequency during peak hours of the day and seasons of the year (although non-storm-related risk is nearly constant through the year), that there is strong statistical support for a power-law statistical relationship between blackout size and frequency, and that blackout sizes and blackout durations are not correlated. These trends hold even after controlling for increasing demand and population and after eliminating small events, for which the data may be skewed by spotty reporting. These patterns have important implications for those who make investment and policy decisions in the electricity industry; for example, the fat-tail distribution means that it is important to design electricity infrastructure to be robust to large failures rather than focusing narrowly on small failures.

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