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A number of reliability indexes are used in the electric industry to make it easier to compare <br /> performance of electric utilities. These reliability indexes are: <br /> Average Service Availability Index (ASAI) <br /> ASAI is a measure of the average availability of the sub-transmission and distribution <br /> systems to serve customers. It is the ratio of the total customer minutes that service was <br /> available to the total customer minutes available in a time period. This is normally expressed <br /> as a percentage. <br /> ERMU's 2013 ASAI is 99.999% Availability. Last year was 99.999% Availability. <br /> Customer Average Interruption Duration Index (CAIDI) <br /> CAIDI is defined as the average duration (in minutes) of an interruption experienced <br /> by customers during a specific time frame. It is calculated by summing the customer <br /> minutes off during each interruption in the time period and dividing this by the number of <br /> customers experiencing one or more sustained interruptions during the time period. The <br /> resulting unit is minutes. The index enables utilities to report the average duration of a <br /> customer outage for those customers affected. <br /> ERMU's 2013 CAIDI is 118.23 minutes. Last year's CAIDI was 66 minutes. <br /> System Average Interruption Duration Index (SAIDI) <br /> SAIDI is defined as the average interruption duration for customers served during a specified <br /> time period. It is determined by summing the customer minutes off for each interruption <br /> during a specified time period and dividing that sum by the average number of customers <br /> served during that period. The unit is minutes. This index enables the utility to report how <br /> many minutes' customers would have been out of service if all customers were out at one <br /> time. <br /> ERMU's 2013 SAIDI is 5.97 minutes. Last year's SAIDI was 7.7 minutes. <br /> System Average Interruption Frequency Index (SAIFI) <br /> SAIFI is defined as the average number of times that a customer is interrupted during a <br /> specified time period. It is determined by dividing the total number of customers interrupted <br /> in a time period by the average number of customers served. The resulting unit is <br /> "interruptions per customer." <br /> ERMU's 2013 SAIFI is 0.0505. Last year's SAIFI was 0.117. <br /> Another statistic staff gets concerned about is the average length of any outage. Elk River <br /> Municipal Utilities' 2013 average length of outage was 120.61 minutes. In 2012 the average <br /> "+ l l Ei E R E R 11 <br /> Page 2 of 4 INATUREI <br /> Reliable Public <br /> Power Provider POWERED T o S E R V E <br /> 176 <br />