ASUI

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

$$\mbox{ASUI} = \frac{\sum{U_i N_i}}{\sum{N_i} \times 8760} = 1- \mbox{ASAI}$$

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

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