EIA data compares the frequency and duration of electric power outages
Disruptions in electricity service are distinguished by both frequency and duration, the U.S. Energy Information Administration (EIA) said on Monday, with values varying amongst the many electric distribution systems servicing approximately 145 million U.S. customers.
The duration, frequency and scale of service interruptions determine the reliability of an electricity supply system. Many of the standards for reporting such values were established by the Institute of Electrical and Electronics Engineers (IEEE), a professional trade institute for electric and information technologies or related fields. Any interruptions longer than five minutes are reported with outage frequency and duration values to the EIA.
Reporting utilities may decide if an outage occurred during a major event, including snowstorms, hurricanes, floods or heatwaves. Periods of outages vastly different from a utility’s five-year history may also be considered a major event. Not every utility is consistent in what is considered a major event.
Investor-owned utilities (IOU), cooperative energy utilities (co-ops) and municipal outage reports collectively represented 28 percent of all utilities in 2015, but accounted for approximately 72 percent of electricity sales.
Municipal utility customers reported the lowest instance of disturbances in both frequency and duration, averaging one outage and two hours of interruption in 2015. Considering major events, investor-owned utilities averaged approximately three hours of disruption. Co-ops reported approximately five hours without power and comparatively twice as many outages on average.
A utility’s quality of service can be affected by factors including weather, population density and tree density. Co-ops often supply service to rural homes, with more power line miles and trees per customer, and with storms more likely to affect distribution. Municipalities typically service customers in high-density urban areas, with fewer power line miles per customer or even underground distribution lines.
