Utilities use several indices to measure system reliability. Three of the most common indices are System Average Interruption Duration Index (SAIDI), System Average Interruption Frequency Index (SAIFI) and Momentary Average Interruption Frequency Index (MAIFI). SAIDI is an industry measurement for the annual outage minutes experienced by a utility's customers. SAIFI is an industry measurement representing the average number of power outages a customer will experience each year. MAIFI is very similar to SAIFI but it tracks the average frequency of momentary interruptions not exceeding five minutes. In all three indices, lower numbers indicate better performance from the utility.
Roseville Electric's SAIDI, SAIFI and MAIFI numbers, as compared to PG&E, SMUD and Redding Electric utilities, clearly represent Roseville Electric's excellent system reliability.