ASUI

The Average Service Unavailability Index (ASUI)^[1] is a reliability index commonly used by electric power utilities. It is calculated as

${\displaystyle {\mbox{ASUI}={\frac {\sum {U_{i}N_{i}{\sum {N_{i}\times 8760}=1-{\mbox{ASAI}$

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

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