Table 11.1 Reliability Metrics of U.S. Distribution System

IEEE Any Method
All Events (With Major Event Days) Without Major Event Days Loss of Supply Removed All Events (With Major Events) Without Major Events
Year SAIDI
(minutes per year)
SAIFI
(times per year)
CAIDI
(minutes per interruption)
SAIDI
(minutes per year)
SAIFI
(times per year)
CAIDI
(minutes per interruption)
SAIDI
(minutes per year)
SAIFI
(times per year)
CAIDI
(minutes per interruption)
SAIDI
(minutes per year)
SAIFI
(times per year)
CAIDI
(minutes per interruption)
SAIDI
(minutes per year)
SAIFI
(times per year)
CAIDI
(minutes per interruption)
2013 227.2 1.187 191.5 111.9 0.994 112.6 225.5 1.113 202.6 215.7 1.2 179.8 106.1 0.992 106.9
2014 236.2 1.257 188 114.2 1.038 110 244.8 1.202 203.7 219 1.22 179.6 109.7 1.019 107.7
2015 209 1.275 163.9 117 1.073 109.1 198.2 1.163 170.4 205 1.246 164.5 113.1 1.046 108.1
2016 268.4 1.327 202.2 119.8 1.082 110.7 257 1.23 209 249.2 1.292 192.9 116.9 1.062 110
2017 505.9 1.42 356.2 117 1.023 114.3 489.6 1.254 390.6 473.1 1.394 339.3 114.4 1.007 113.6
2018 349.2 1.34 260.5 121.4 1.051 115.5 338.5 1.193 283.8 346.4 1.325 261.5 117.2 1.028 114
2019 295.5 1.332 221.8 122.2 1.04 117.5 289.1 1.189 243 284.6 1.325 214.8 118.6 1.017 116.6
2020 456.1 1.385 329.3 116 1.013 114.5 460.5 1.238 371.9 491.9 1.44 341.7 119 1.037 114.7
2021 475.8 1.436 331.2 125.7 1.039 120.9 404.5 1.294 312.6 440 1.425 308.8 121.5 1.025 118.5
2022 333 1.426 233.5 131.1 1.09 120.2 324.7 1.315 246.9 335.5 1.405 238.8 125.7 1.064 118.1
2023 366.6 1.348 271.8 123.9 1.022 121.3 357.7 1.242 288 342 1.333 256.6 118.4 0.999 118.5

SAIDI = System Average Interruption Duration Index. It is the minutes of non-momentary electric interruptions, per year, the average customer experienced.
SAIFI = System Average Interruption Frequency Index. It is the number of non-momentary electric interruptions, per year, the average customer experienced.
CAIDI = Customer Average Interruption Duration Index. It is average number of minutes it takes to restore non-momentary electric interruptions.
IEEE refers to the IEEE 1366-2003 or the IEEE 1366-2012 standard. Any method combines data from utilities that use IEEE standard with data from utilities that do not.
For utilities using the IEEE method, a Major Event Day is any day that exceeds a daily SAIDI threshold called Tmed. Tmed is a duration statistic calculated from
daily SAIDI values from the past five years. For utilities not using IEEE methods, Major Events are self-determined by the reporting utility.
Loss of Supply Removed excludes outages due to loss of supply from the high-voltage/bulk power system.
For a five minute video explanation of these metrics, go to https://youtu.be/oVH9L0fCMTU.
Source: U.S. Energy Information Administration, Form EIA-861, Annual Electric Power Industry Report.