Since 2013, excluding major events, the annual average duration of power interruptions has consistently hovered around two hours. Factors contributing to major power disruptions include weather-related incidents, vegetation interference near power lines, and specific utility practices. To assess the reliability of U.S. electric utilities, two key indexes are utilized:
The influence of major events on electrical reliability is gauged by comparing affected states' SAIDI and SAIFI values against the U.S. average, which was 5.6 hours of outages and 1.4 outages per customer in 2022. The year witnessed 18 weather-related disasters in the U.S., each resulting in over $1 billion in damages. Noteworthy major events include:
In 2022, states like Florida, West Virginia, Maine, Vermont, and New Hampshire experienced the most prolonged power interruptions, with New Hampshire averaging 10.3 hours and Florida 19.1 hours. Conversely, the District of Columbia, Delaware, Rhode Island, Nebraska, and Iowa had the shortest total interruptions, with the District of Columbia averaging just 34 minutes and Iowa 85 minutes.
The frequency of outages, unlike their duration, is more often linked to non-major events. Across the nation, Alaska recorded the highest number of power disruptions per customer (averaging 3.5), followed by several heavily forested states like Tennessee and Maine. Power outages due to falling tree branches are common, particularly during winter storms that burden tree limbs and power lines. The District of Columbia stood out with the shortest and fewest outages per customer.