Reliable electric service is a critical public need. Our nation’s economic success and security depend upon our ability to preserve this fundamental resource. The availability of 24/7 uninterrupted electricity is a basic societal expectation, especially in today’s digital, Internet of Things-connected world. As we modernize the grid, we are also improving reliability for customers.

Grid Reliability

We track our transmission and distribution reliability performance with several industrywide metrics. These indicators show us how reliable our system is and how our customers are impacted when it is not. They do not include major storms. The investments we are making in our transmission and distribution system improve reliability and operating efficiency and prepare the system for new technologies.

The System Average Interruption Duration Index (SAIDI) represents how many minutes the average customer experiences an interruption in electric service in a given year. During 2016, the AEP System SAIDI was 216.3 minutes, excluding major events, a 5.8 percent improvement from 2015. The growth of vegetation contributed to about 32 percent of SAIDI results and failure of distribution line equipment accounted for about 19 percent of SAIDI.

The System Average Interruption Frequency Index (SAIFI) represents the number of interruptions experienced by customers in a year. During 2016, the system’s SAIFI was 1.428, a 2.7 percent improvement from 2015. Vegetation and distribution line equipment failures were also the major contributors to SAIFI performance.

The Customer Average Interruption Duration Index (CAIDI) represents the average length of time it takes to restore service when an outage occurs. AEP’s 2016 CAIDI was 151.5 minutes, a 3.1 percent improvement from 2015.