What this data measures

An explorer for grid reliability by state. Switch between SAIDI (the average minutes of interruption a customer experiences per year) and SAIFI (the average number of interruptions per year), and choose whether to include major event days (mostly severe weather), exclude them, or show major events only. Lower values indicate more reliable power delivery.

How this data is constructed

SAIDI and SAIFI data are reported by electric distribution utilities through the EIA Form EIA-861 Reliability Supplement, collected annually since 2013. State values are customer-weighted averages of utility-level reports. "Major events only" is derived as the difference between the including- and excluding-major-events series.

Major event days — typically severe weather — are excluded using the IEEE 1366 standard method. This gives a view of "normal" reliability without the distorting effect of rare catastrophic events.