ASUI

The Average Service Unavailability Index (ASUI)^[1] is a reliability index commonly used by electric power utilities. It is calculated as $ASUI = \frac{\sum U_{i} N_{i}}{\sum N_{i} \times 8760} = 1 - ASAI$

where $N_{i}$ is the number of customers and $U_{i}$ is the annual outage time (in hours) for location $i$ . ASUI can be represented in relation to SAIDI (where annual SAIDI is given in hours) as

$ASUI = \frac{SAIDI}{8760}$