The Average Service Availability Index (ASAI)^[1][2] is a reliability index commonly used by electric power utilities. ASAI is calculated as

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

where ${\displaystyle N_{i))$ is the number of customers and ${\displaystyle U_{i))$ is the annual outage time (in hours) for location ${\displaystyle i}$. 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)

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