APS is one of the nation's most reliable utilities as measured by the average number and duration of service interruptions experienced by the typical customer. The company is a consistent top quartile performer for system reliability in the electric industry. We invest more than $1 billion in the energy grid every year. These investments include new and stronger infrastructure, and advanced grid technologies that will continue to make our top-tier power even more reliable.
We measure customer reliability through two critical standard industry metrics known as SAFI and SADI scores.
- System Average Interruption Frequency Index (SAIFI) which is a measure of the average number of interruptions a customer experiences in a year
- System Average Interruption Duration Index (SAIDI) which measures the number of interrupted minutes a customer experiences in a year.
APS has achieved excellent performance in both areas over the past decade, including reducing the frequency of customer outages by 30% and duration of customer outages by 19%. This accomplishment is the result of reliability programs, system improvement projects and investments in technology.