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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 as <br /> a percentage. <br /> ERMU's 2014 ASAI is 99.9913% Availability. ERMU's 2013 ASAI 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 by <br /> customers during a specific time frame. It is calculated by summing the customer minutes off <br /> during each interruption in the time period and dividing this by the number of customers <br /> experiencing one or more sustained interruptions during the time period. The resulting unit is <br /> minutes. The index enables utilities to report the average duration of a customer outage for those <br /> customers affected. <br /> ERMU's 2014 CAIDI is 199.884 minutes. ERMU's 2013 CAIDI was 118.23 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 during <br /> a specified time period and dividing that sum by the average number of customers served during <br /> that period. The unit is minutes. This index enables the utility to report how many minutes' <br /> customers would have been out of service if all customers were out at one time. <br /> ERMU's 2014 SAIDI is 44.056 minutes. ERMU's 2013 SAIDI was 5.97 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 specified <br /> time period. It is determined by dividing the total number of customers interrupted in a time <br /> period by the average number of customers served. The resulting unit is"interruptions per <br /> customer." <br /> ERMU's 2014 SAIFI is 0.22. ERMU's 2013 SAIFI was 0.0505. <br /> Another statistic staff gets concerned about is the average length of any outage. Elk River <br /> Municipal Utilities' 2014 average length of outage was 140.16 minutes. In 2013 the average <br /> length of outage was 116.84 minutes. Electric utilities with a high percentage of underground <br /> PONEDED D1 <br /> Page 2 of 3 NATURE <br /> Reliable Public <br /> Power Provider POWERED T o S E R V E <br /> 61 <br />