Severe weather is the leading cause of power outages in the United States, according to a U.S. Government report. Damaged power lines don’t make for such dramatic photos as flooded nuclear power plants or oil refineries (see previous post), but they represent the most vulnerable part of the energy sector.
The first chart at right shows the annual number of reported power outages in the United States. Severe weather accounts for 58% of them, and 87% of large outages affecting 50,000 or more customers. In all, 679 widespread outages occurred 2003-2012 due to severe weather – that’s about 68 widespread outages a year.
How does the United States compare to other developed nations? Comparisons may not be entirely valid, as different nations are subject to very different weather conditions. Nevertheless, all nations experience severe weather, and the table below reports two statistics used to make such comparisons. The SAIDI represents the average amount of time per year that power supply to a customer is interrupted (in minutes). The SAIFI represents the average number of times per year the power supply to a customer is interrupted.
Comparison of International Reliability Indices:
data from Campbell, Weather-Related Power Outages and Electric System Resilience.
Missouri has not been immune from storm-related power outages. The National Electrical Reliability Corporation maintains a yearly summary of power outages, with usable data back to 2002. The third graph at right shows the annual number of customers in Missouri experiencing a power outage from 2002 through July of 2013. The chart is dominated by a huge spike in 2006. This was the result of storms that took down much of the power grid in the St. Louis Metropolitan Area. Some of the affected customers were in Illinois, but the data does not separate them from the total. During this event, many customers were affected by repeated outages from a series of storms, and each outage has been counted separately.
The data is not sufficient to infer a trend. Generally, the number of outages in Missouri seems episodic, depending on the weather in a given year. However, it suggests that Missouri’s power grid remains vulnerable to severe weather, as does the national grid.
Executive Office of the President. (2013). Economic Benefits of Increasing Electric Grid Resilience to Weather Outages. http://energy.gov/downloads/economic-benefits-increasing-electric-grid-resilience-weather-outages.
Campbell, Richard J. (2012). Weather-Related Power Outages and Electric System Resilience. Washington, DC: Congressional Research Service 7-7500. http://www.fas.org/sgp/crs/misc/R42696.pdf.