In-brief analysis
December 1, 2025
U.S. electricity customers experienced an average of 11 hours of electricity interruptions in 2024, or nearly twice as many as the annual average experienced in the decade before, according to our Electric Power Annual 2024 report. Major events such as Hurricanes Beryl, Helene, and Milton accounted for 80% of the hours without electricity in 2024.
Utilities categorize interruptions depending on if they are attributed to major events such as hurricanes or other storms, interference from vegetation near power lines, or atypical utility operations. When comparing outages across years, most of the differences in total time without service are attributed to major events.
Interruptions attributed to major events averaged nearly nine hours in 2024, compared with an average of nearly four hours per year in 2014 through 2023. Service interruptions that aren’t triggered by major events routinely average about two hours per year.
Annual outages are characterized by two industry metrics:
- The System Average Interruption Duration Index (SAIDI) measures the total duration an average customer experiences non-momentary power interruptions in a one-year period.
- The System Average Interruption Frequency Index (SAIFI) measures the number of interruptions in a year.
Data source: U.S. Energy Information Administration, Electric Power Annual 2024
Data values: Distribution System Reliability, SAIDI and SAIFI values of U.S. distribution system by state
States with the most time without power dealt with major weather events in 2024. In July, Hurricane Beryl left 2.6 million customers without power in Texas. In September, Hurricane Helene left 5.9 million customers without power across 10 states; at least 1.2 million of those customers were in South Carolina.
Customers in South Carolina experienced longer service interruptions than in any other state, at nearly 53 hours in 2024. South Carolina, North Carolina, and Florida dealt with strong winds and flooding from Hurricane Helene that affected transmission and distribution power lines as well as substations leading to prolonged power outages. The next month, Hurricane Milton left 3.4 million customers in Florida without power.
In contrast, customers in states such as Arizona, South Dakota, North Dakota, and Massachusetts experienced, on average, less than two hours of service interruptions in 2024.
Some states experienced outages more frequently than the U.S. average (1.5 instances) in 2024. For example, Hawaii electricity customers experienced 4.4 electricity interruptions in 2024, the most of all states. The more frequent interruptions in Hawaii are mainly due to adverse weather, volcanic activity, unexpected outages at oil-fired plants, and issues connecting new generating capacity.
States such as Maine and Vermont also tend to have more frequent outages, often attributed to storm-related damage to trees that affects power lines. In contrast, states such as South Dakota, Maryland, Illinois, and Massachusetts experienced, on average, less than one power interruption last year.
Principal contributors: Kimberly Peterson, Lindsay Aramayo
