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2. CAIDI (customer average interruption duration index) <br />This is defined as the average length of an interruption weighted by the number of customers affected. <br />It is calculated by summing the customer minutes off during each interruption in the time period and <br />dividing this by the number of customers. experiencing one or more sustained interruptions during the <br />time period. The resulting unit is minutes. The index enables utilities to report the average duration <br />of a customer outage for those customers affected. <br />ERMU's 2009 CAIDI is 137 minutes. Last year's CAIDI was 28 minutes. <br />3. SAIDI (system average interruption duration index) <br />This is defined as the average interruption duration for customers served during a specified time <br />period. It is determined by summing the customer minutes off for each interruption during a specified <br />time period and dividing that sum by the average number of customers served during that period. The <br />unit is minutes. This index enables the utility to report how many minutes customers would have <br />been out of service if all customers were out at one time. <br />ERMU's 2009 SAIDI is 5.1 minutes. Last year's SAIDI was 17.3 minutes. <br />4. SAIFI (system average interruption frequency index) <br />This is defined as the average number of timers that a customer is interrupted during a specified time <br />period. It is determined by dividing the total number of customers interrupted in a time period by the <br />average number of customers served. The resulting unit is "interruptions per customer." <br />ERMU's 2009 SAIFI is 0.037. Last year's SAIFI was 0.618. <br />Another statistic staff gets concerned about is the average length of any outage. Elk River Municipal <br />Utilities' 2009 average length of outage is 109.3 minutes. Last year the average length of outage was <br />99.3 minutes. Electric utilities with a high percentage of underground facilities will exhibit higher length <br />of outage time than electric utilities with more overhead facilities. <br />Staff has reviewed these statistics in detail to find ways to improve. These statistics are very good <br />compared to other utilities. While other utility stats are difficult to obtain, these are some typical numbers <br />we have found: <br /> ERMU <br />2009 Connexus <br />2008 MN Power <br />2008 <br />CAIDI 137 min 78 min 100 min <br />SAIDI 5.1 min 29 min 114 min <br />SAIFI 0.037 0.372 1.140 <br />