Appropriate-Use Disclaimer

Informational only — not professional advice

The reliability metrics on this site are provided for general information and do not constitute engineering, safety, financial, real-estate, insurance, or legal advice. Do not rely on them as the sole basis for a decision about where to live, what to pay, or how to prepare for power loss. For decisions that depend on power reliability, consult the utility directly and a qualified professional.

What SAIDI and SAIFI describe

SAIDI (System Average Interruption Duration Index) and SAIFI (System Average Interruption Frequency Index) are system-wide averages for an entire utility, computed under IEEE Standard 1366 and self-reported to the EIA. A SAIDI of 90 minutes means that, averaged across all of the utility's customers over the year, the typical customer experienced about 90 minutes of interruption. Your specific address, circuit, or neighborhood may experience materially more or less than the system average. These indices do not tell you whether your particular home will lose power.

Historical, not a forecast

Every figure reflects a past reporting year (the data on the site spans 2020–2023). Reliability changes year to year with weather, investment, and grid conditions. Past performance is not a guarantee of future reliability.

Major-event days

Headline SAIDI and SAIFI include outages from major events such as severe storms, hurricanes, and ice storms. We also show the "without major event days" (nMED) values, which exclude those events to better reflect day-to-day infrastructure performance. A single catastrophic storm year can raise a utility's headline numbers sharply even if its everyday reliability is strong; read both figures together.

Voluntary, self-reported data

Reliability reporting in EIA Form 861 is voluntary, and utilities calculate their indices under their own implementation of IEEE 1366. Not every utility reports every year, and methods can differ between utilities. Comparisons are most meaningful within the same metric and year. Where a utility has not reported, we do not estimate a value for it.

Verify against the source

For the authoritative figures, consult the U.S. Energy Information Administration's Form 861 data directly. If you believe a number on PlainUtility is wrong, please tell us through our corrections process.