Black Hills Power reduced its SAIDI from 2,642 minutes to 2 minutes — a 99.9% improvement through systematic grid hardening and underground cable replacement. Northern States Power Minnesota improved from 564 to 55 minutes through sustained capital investment. These utilities demonstrate that dramatic reliability improvements are achievable within a single regulatory period.
At the other end, Tampa Electric deteriorated from 100 to 4,240 minutes due to Hurricane Milton in 2024. Duke Energy Carolinas went from 247 to 7,804 minutes due to Hurricane Helene. These hurricane-driven outliers illustrate why regulators increasingly separate SAIDI with and without major event days — the IEEE MED standard included here captures total customer experience but conflates weather exposure with utility investment quality.
The most analytically useful resilience finding is identifying utilities that show deteriorating SAIDI in non-hurricane years — these signal structural grid investment gaps that rate proceedings should address. Utilities that improve SAIDI despite hurricane exposure through hardening investments demonstrate that weather vulnerability is not inevitable.
| Utility | St | SAIDI at First Report | SAIDI in 2024 | Change | Trend |
|---|
| Year | SAIDI | Long-run Change |
|---|---|---|
| 2024 | — | — |
| 2023 | — | — |