Average Service Availability Index

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

$\text{ASAI}=\frac{\sum N_i\times 8760-\sum U_i{N}_i}{\sum N_i\times 8760}$

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)

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