This article was published by the US Energy Information Administration on Jan. 25, 2024.
By Alex Gorski
On average, U.S. electricity customers experienced approximately five and one-half hours of electricity interruptions in 2022, almost two hours less than in 2021, according to our recently released Annual Electric Power Industry Report. The annual decline was driven by fewer major events in 2022 compared with 2021.
Since 2013, the average duration of electricity interruptions each year has remained consistently around two hours after excluding major events. Major events that cause power interruptions include weather, interference from vegetation near power lines, and utility practices. We measure U.S. electric utility reliability using two indexes:
- The System Average Interruption Duration Index (SAIDI) measures the total duration (in hours) an average customer experiences non-momentary power interruptions in a one-year period.
- The System Average Interruption Frequency Index (SAIFI) measures the frequency of interruptions in number of occurrences.
We measure the impact these major events have on electricity reliability by comparing the SAIDI and SAIFI values of the affected states with the U.S. average (5.6 hours of outages and 1.4 outages per customer). In 2022, the United States had 18 weather-related disasters that exceeded $1 billion dollars in damages per event. Notable major events include the following:
- In September 2022, Hurricane Ian left over 2.6 million customers in Florida without power, some for over two weeks.
- In November 2022, Hurricane Nicole left over 300,000 customers in Florida without power.
- In December 2022, Winter Storm Elliott left over 1.5 million customers in several states without power (including Texas, Florida, Arkansas, Tennessee, West Virginia, and Wisconsin) and dumped as much as four feet of snow in parts of New York.
Customers in Florida, West Virginia, Maine, Vermont, and New Hampshire experienced the most interrupted power in 2022, ranging from an average of 10.3 hours in New Hampshire to 19.1 hours in Florida. Nationwide, electricity customers in the District of Columbia, Delaware, Rhode Island, Nebraska, and Iowa had the shortest total electricity interruptions in 2022, ranging from an average of 34 minutes in the District of Columbia to 85 minutes in Iowa.
A higher average frequency of outages, unlike average duration, tends to be associated more with non-major events. Nationwide, Alaska had the most power interruptions per customer (3.5 interruptions on average), followed by Tennessee, Maine, West Virginia, and Vermont, all of which are heavily forested states. Power interruptions resulting from falling tree branches are common, especially because of winter ice and snowstorms that weigh down tree limbs and power lines. The District of Columbia had both the shortest outages and the fewest number of interruptions per customer.