SAIDI
System Average Interruption Duration Index – average total duration of power interruptions per customer in a period
What is SAIDI?
The System Average Interruption Duration Index, known as SAIDI, is the average total time a customer is without supply in a period. It is a standard reliability measure for electricity, gas and water networks.
It shows how long customers experience outages, and regulators often use it to judge network performance.
How this KPI is measured
- Function
- Operations & Supply Chain
- Sub-function
- Asset Reliability
- Industry
- Energy & Utilities
- Type
- Lagging
- Impact
- Operational
- Unit
- min
- Measurement frequency
- Monthly
- Formula
- Sum of (outage duration × customers affected) / Total customers served
How to calculate it
Add up, for each outage, the duration multiplied by the number of customers affected, and divide by the total number of customers served.
For example, if outages caused 6,000,000 customer-minutes of interruption across 100,000 customers, SAIDI is 60 minutes per customer.
Use consistent rules on which outages count, such as excluding planned work or major events, according to the regulatory definition.
Where it is used
Meeting regulatory targets
Report reliability.
Prioritising network investment
Find weak areas.
Comparing periods and regions
Track improvement.
How to improve it
Tips and common mistakes
- Use with SAIFI to separate frequency from duration.
- Follow the exact definition your regulator uses.
- Look at worst-served customers as well as the average.
More Operations & Supply Chain kpi library
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