Photo by Ed Metz, Dreamstime.
Ed Metz Dreamstime

US Ratepayers See 7 Hours of Outages on Average Last Year

Nov. 28, 2022
This is about one hour less, on average, than in 2020.

On average, U.S. electricity customers experienced just over seven hours of electric power interruptions in 2021, almost an hour less than in 2020, according to the Energy Information Administration’s data.

When major events—including snowstorms, hurricanes, and wildfires—are excluded, the average total duration of interruptions that customers experienced annually from 2013 to 2021 was consistently around two hours.

Different factors cause power interruptions, including weather, vegetation patterns around power lines, and utility practices. Utilities can report interruption duration values with major events, without major events, or both.

One metric used to measure the reliability of U.S. electric utilities is the System Average Interruption Duration Index (SAIDI), which measures the total time an average customer experiences a non-momentary power interruption in a one-year period. SAIDI is often paired with the System Average Interruption Frequency Index (SAIFI), which measures the frequency of interruptions.

Electricity customers in the District of Columbia, Delaware, Florida, North Dakota, and Nevada had the shortest total time of electricity interruptions in 2021, ranging from 52 minutes in the District of Columbia to 102 minutes in Nevada.

Customers in Louisiana, Oregon, Texas, Mississippi, and West Virginia experienced the most time with interrupted power in 2021, ranging from almost 19 hours in West Virginia to over 80 hours in Louisiana. Louisiana also had the highest average number of power interruptions, followed by Texas. The long interruptions were largely because of extreme weather events. The United States experienced 21 named storms in 2021, the third-most active Atlantic weather season on record. In addition to four major hurricanes, a winter storm affected the central United States with Arctic air as far south as Texas.

In February 2021, winter storm Uri hit Texas, where about 4.5 million customers lost power, along with almost half a million customers in Louisiana and Oklahoma. The storm moved into the mid-Atlantic region, knocking out power in West Virginia and Kentucky. Both West Virginia and Kentucky are heavily forested, so power interruptions resulting from falling tree branches are common, especially as a result of winter ice and snowstorms that weigh down tree limbs and power lines. Oregon had both extreme heat and cold weather events, including a historic ice storm in February 2021 and the Bootleg wildfire in August 2021.

In late August 2021, Hurricane Ida left 1.2 million customers in Louisiana without power, some for over two weeks, and it left almost 150,000 customers without power in Mississippi. Hurricane Nicholas followed about two weeks later, leaving half a million customers without power in Texas as well as parts of Mississippi and Louisiana.

In addition to power interruption duration, reliability can also be measured in terms of the frequency of power interruptions. Maine historically has the most frequent electric power interruptions, averaging 3.0 interruptions annually from 2013 through 2021, followed by Louisiana (2.5 interruptions) and West Virginia (2.4 interruptions). Maine is a heavily forested state where power interruptions resulting from falling tree branches are common.

In 2021, Maine was the state with the third-highest electric power interruption frequency (2.5 interruptions), behind Louisiana (3.3 interruptions) and Texas (2.9 interruptions), primarily because of several significant storms in the South Central region. Mississippi (2.4 interruptions) was also affected by the storms. West Virginia, another heavily forested state with a history of frequent interruptions, had 2.4 interruptions per customer in 2021. In contrast, the District of Columbia (0.5 interruptions), Nevada (0.8 interruptions), New York (0.9 interruptions), North Dakota (0.9 interruptions), and Connecticut (0.9 interruptions) where well below the U.S. average of 1.4 power interruptions per customer.

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