How OutageRiskCheck Reads Your Utility's Outage Record

Three numbers every utility files

The EIA's Form 861 reliability file asks each utility for three averages across its customers for the year. SAIDI is total minutes without power per customer. SAIFI is how many separate outages the average customer had. CAIDI is SAIDI divided by SAIFI - how long one outage lasts before power comes back. Across 964 reporting utility-state records, the median is 172 minutes a year, 1.4 outages, and 120 minutes per outage.

Storm days are left in, on purpose

Utilities can report SAIDI with or without "major event days" - the handful of days a year a big storm knocks out a large share of the system. This site uses the figure with those days included, because that is what customers actually lived through, and long storm outages are exactly what a generator is for. The trade-off is that one bad storm year can push a utility's number up; see why one storm can swing the number.

Two reporting standards

752 records follow the IEEE 1366 standard, which defines exactly what counts as an outage (interruptions over five minutes) and a major event day. The other 212 follow the utility's own method, so their figures are less strictly comparable. 12 utility-state records filed no reliability figures at all; their pages say so rather than inventing a number.

How the verdict is built

The generator verdict comes only from SAIDI, ranked against every other reporting utility: under the 25th percentile (71 minutes) is rare, up to the median is below average, up to the 75th percentile (349 minutes) is above average, up to the 90th (707 minutes) is high, and beyond that is severe. The type of backup that fits comes separately from CAIDI - see how often vs how long. These bands are this site's own; the EIA does not publish a reliability rating.

Where to go next

See the range across large utilities: Great Lakes Energy Coop, MI, Evergy Missouri West, MO, Nashville Electric Service, TN.

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