Average Service Availability Index

The Average Service Availability Index (ASAI) is a reliability index commonly used by electric power utilities. ASAI is calculated as

${\mbox{ASAI}}={\frac {\sum {N_{i}}\times 8760-\sum {U_{i}N_{i}}}{\sum {N_{i}}\times 8760}}$

where $N_{i}$ is the number of customers and $U_{i}$ is the annual outage time (in hours) for location $i$. ASAI can be represented in relation to SAIDI (when the annual SAIDI is given in hours, 8760 is the number of hours in a year)

${\mbox{ASAI}}=1-{\frac {\mbox{SAIDI}}{8760}}$