System Average Interruption Duration Index (SAIDI)

SAIDI is the average number of hours of service interruption experienced by each customer in one year. Widely used by electricity distribution organizations, it is often used alongside System Average Interruption Frequency Index (SAIFI) to distinguish many short interruptions from a few longer interruptions.

The US Energy Information Administration collects SAIDI and SAIFI data for three categories of electricity distributor – municipals (owned by cities), co-ops (owned by members); and investor owned (owned by shareholders). In 2016, municipals’ customers experienced the lowest SAIDI and SAIFI of the three categories.