Average Service Availability Index

The Average Service Availability Index (ASAI){{cite web |url-status=dead

\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}