The Average Service Availability Index (ASAI)[1][2] is a reliability index commonly used by electric power utilities.
ASAI is calculated as
is the annual outage time (in hours) for location
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}}}