What SAIDI and SAIFI mean

What the numbers mean

SAIDI = total customer minutes of interruption divided by customers served. SAIFI = total customer interruptions divided by customers served. CAIDI = SAIDI divided by SAIFI, the average length of one outage.

For 673 U.S. utilities in the 2024 file the median SAIDI is 99 minutes, about 1.7 hours a year. One utility in ten reports 293 minutes or more. The median SAIFI is 1.01 interruptions a year.

Major event days change the picture

Utilities report SAIDI twice: without major event days and with all events. Tampa Electric Co reports 70 minutes without major events and 4,240 with them, because storms and other major events add many minutes. Compare the first figure for everyday service and the second for storm exposure.

The split exists because a hurricane or ice storm can swamp a year of ordinary outages. Which days count as major events is set by a statistical rule in the IEEE standard, not by the utility's choice; the rule is the same for everyone, but the reported value still depends on how well each utility's systems count outages.

How the 2024 reports are spread

The median hides a long tail. The table shows where 10%, 25%, 50%, 75% and 90% of reporting utilities fall.

Source: EIA-861 2024, Reliability: 673 utilities reporting SAIDI under the IEEE method, without major events. Retrieved 2026-10-02. CSV, 5 rows.

Best and worst of the large utilities

Utilities with 100,000 or more home accounts, 2024. The first six rows are the lowest SAIDI, the last six the highest.

Source: EIA-861 2024, Reliability (IEEE method); utilities with 100,000+ home accounts. Retrieved 2026-10-02. CSV, 135 rows.

By state

State medians of the utilities that report. A state with a few large utilities and many small co-ops will look different from one with a single big utility, so read this next to the company table, not in place of it.

Source: EIA-861 2024, Reliability; states with 5+ reporting utilities; six lowest then six highest. Retrieved 2026-10-02. CSV, 39 rows.

The median over ten years

The chart is the median across reporting utilities in each year, without major events. A flat line means typical reliability has not moved much; it says nothing about any one utility.

Limits

Not every utility reports under the IEEE method, and a few report other measures. Zero or a dot in the EIA file means the utility did not report; this site shows no data in that case. A utility's SAIDI also depends on how rural it is: long lines and few customers per mile make for longer outages. The numbers do not say how much power was out in each storm.

Key facts and where they come from

CSV, 11 rows.

Related guides

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• Why your electric bill changes by season
• How to read your electric bill