ASUI

The Average Service Unavailability Index (ASUI) is a reliability index commonly used by electric power utilities. It is calculated as $\text{ASUI}=\frac{\sum U_i{N}_i}{\sum N_i\times 8760}=1-\text{ASAI}$ 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 $\text{ASUI}=\frac{\text{SAIDI}}{8760}$