The Average Service Availability Index (ASAI) is a

reliability index Reliability index is an attempt to quantitatively assess the reliability of a system using a single numerical value. The set of reliability indices varies depending on the field of engineering, multiple different indices may be used to characterize ...

commonly used by

electric power Electric power is the rate of transfer of electrical energy within a electric circuit, circuit. Its SI unit is the watt, the general unit of power (physics), power, defined as one joule per second. Standard prefixes apply to watts as with oth ...

utilities A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service (often also providing a service using that infrastructure). Public utilities are subject to forms of public control and r ...

. ASAI is calculated as

\mbox = \frac

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 A Ṣa‘īdī (, Coptic language, Coptic: ⲣⲉⲙⲣⲏⲥ ''Remris'') is a person from Upper Egypt (, Coptic language, Coptic: ⲙⲁⲣⲏⲥ ''Maris''). Etymology The word literally means "from Ṣa‘īd" (i.e. Upper Egypt), and can al ...

(when the annual SAIDI is given in hours, 8760 is the number of hours in a year)

\mbox = 1 - \frac

References

{{Reliability indices Electric power distribution Reliability indices