Reliability Stats

There are four indices that GUS Electric and the electric industry track to compile reliability statistics. GUS Electric participated in an Electric Distribution Reliability Best Practices Survey that benchmarked reliability statistics with nearly 100 electric utilities across the nation. A description of the indices, GUS Electric's current results, and the results of the benchmarking survey are as follows:

1.ASAI (Average Service Availability Index) - The ratio of total customer hours that service was available divided by the total customer hours demanded in a time period. It is expressed as a percent. GUS Electric's ASAI for calendar year 2005 was 99.994%. The benchmarking survey did not include this index.

2.CAIDI (Customer Average Interruption Duration Index) - Defined as the average length of an interruption, weighted by the number of customers affected, for customers interrupted during a specific time period. It is calculated by summing the customer-minutes off during each interruption in the time period and dividing the sum by the number of customers experiencing one or more sustained interruptions (greater than one minute) during the time period. The resulting unit is minutes. The index enables utilities to report the average duration of a customer outage. GUS Electric's CAIDI for calendar year 2005 was 146.60 minutes. The benchmarking survey CAIDI average was 320 minutes.

3.SAIDI (System Average Interruption Duration Index) - Defined as the average interruption duration for customers served during a specified time period. Determined by summing the customer-minutes off for each interruption during a specified time period and dividing the sum by the average number of customers served during that period. The unit is minutes. The index enables the utility to report how many minutes customers would have been out of service if all customers were out at one time. GUS Electric's SAIDI for calendar year 2005 was 31.51 minutes. The benchmarking survey SAIDI average was 95 minutes.

4.SAIFI (System Average Interruption Frequency Index) - Defined as the average number of times that a customer is interrupted during a specified time period. Determined by dividing the total number of customers interrupted in a time period by the average number of customers served. The index is calculated for interruptions of more than one minute (SAIFI-long) and less than one minute (SAIFI-short). The resulting unit is "interruptions per customer." GUS Electric's SAIFI for calendar year 2005 was .21 interruptions per customer. The benchmarking survey SAIFI average was 1.2 interruptions per customer.

GUS Electric starts by collecting data on outages throughout the year by way of field crews preparing Outage Reports with information like date the outage occurred, time the outage started, time of crew arrival at outage, time power was restored (both all at once and in stages), and the number of customers affected by the outage. We take the number of customers affected and multiply it by the number of minutes in the outage duration to calculate Customer Minutes.

The two main uses of this information are:

a. To provide a benchmark which assists us in determining if we are meeting industry standards and providing quality electric service and

b. To identify areas that experience multiple/frequent outages for preventive maintenance. GUS Electric has identified the need for an accelerated preventive maintenance program in our 5-year Strategic Plan. We are taking steps to insure our goals are met. GUS Electric has also expanded contract services for construction and maintenance so our own crews will be able to give our customers that personal attention everyone has grown to expect. When buying a home in Georgetown, make sure GUS Electric serves it!