Understanding SAIDI
How we calculate. SAIDI (minutes) = Σ interruption customer-minutes ÷ customers served. The form uses the same arithmetic as the worked examples on this page. See our methodology and accuracy policy.
Real-world scenario: A typical SAIDI case uses customer-minutes interrupted 2400000 and customers served 100000. Enter the same figures below to reproduce the worked path.
What is SAIDI?
A distribution reliability KPI. Distinct from forced outage rate (generating-unit forced hours÷period) and availability factor.
- Same reporting period
- Customers served = average or end-of-period per policy
- Major event days may be excluded in filings—label your basis
The Formula
Worked Example
Common Use Cases
- Utility reliability reports: SAIDI tracking
- Board scorecards: interruption duration
- Benchmarking: peer SAIDI comparisons
Pro Tips
- State minutes vs hours
- Align IEEE 1366 / regulator exclusions
- Don’t mix generation FOR into SAIDI
Limitations: SAIDI results are educational energy and utilities planning aids—not engineering, grid-operations, or investment advice. Confirm definitions with your ISO/RTO, plant, and regulatory reporting standards.
FAQ
Same as forced outage rate?
No. FOR is generating-unit forced outage hours÷period. SAIDI averages customer interruption duration on the distribution system.
What if customers served is 0?
SAIDI is undefined—enter a positive customers-served count.
Authoritative References
For power system and plant performance concepts, consult: