The national median SAIDI of 209 minutes in 2024 reflects significant hurricane-driven deterioration. Hurricane Helene and Hurricane Milton caused catastrophic outages across the Carolinas and Florida — Duke Energy Carolinas SC recorded 7,804 minutes (130 hours) and Tampa Electric recorded 4,240 minutes. SAIDI includes major event days per IEEE standard, making 2024 a clear outlier driven by weather severity rather than utility performance.
SAIDI measures total minutes without power per customer per year. SAIFI measures how many times customers lose power. CAIDI — the ratio of the two — measures average outage duration. A high CAIDI with moderate SAIFI signals long individual outages typical of transmission failures. A high SAIFI with low CAIDI signals frequent brief outages typical of distribution-level faults.
Black Hills Power at 2 minutes SAIDI in 2024 demonstrates that exceptional reliability is achievable. The 7,802-minute gap between best and worst performers in 2024 is the largest in the dataset history and reflects both weather exposure differences and the cumulative effect of grid investment decisions over decades.
| Utility | St | SAIDI (min/yr) | SAIFI (outages/yr) | CAIDI (min/outage) | Change vs First Year |
|---|
| Year | SAIDI | SAIFI | CAIDI |
|---|---|---|---|
| 2024 | 209 min | 1.34x | 156 min |
| 2023 | 142 min | 1.18x | 120 min |
| 2022 | 151 min | 1.18x | 128 min |
| 2021 | 159 min | 1.26x | 126 min |
| 2020 | 126 min | 1.22x | 103 min |