SAIFI

The System Average Interruption Frequency Index (SAIFI) is commonly used as a reliability indicator by electric power utilities. SAIFI is the average number of interruptions that a customer would experience, and is calculated as

$\text{SAIFI}=\frac{\sum {\lambda }_i{N}_i}{N_T}$

where ${\lambda }_i$ is the failure rate, $N_i$ is the number of customers for location $i$ and $N_T$ is the total number of customers served. In other words,

$\text{SAIFI}=\frac{\text{total number of customer interruptions}}{\text{total number of customers served}}$

SAIFI is measured in units of interruptions per customer. It is usually measured over the course of a year, and according to IEEE Standard 1366-1998 the median value for North American utilities is approximately 1.10 interruptions per customer.

See also

• Average Service Availability Index (ASAI)
• ASIDI
• ASIFI
• ASUI
• CAIDI
• CAIFI
• CTAIDI
• MAIFI
• SAIDI
• SAIFI