UniSource’s electric service ranks among the most reliable in the industry as we rose to the challenge of serving our customers’ changing energy needs amid record-setting heat waves and a public health crisis.
Over the last four years, we have consistently achieved top-quartile reliability rankings among electric utilities across the country. Industry rankings are based on the System Average Interruption Duration Index (SAIDI), a metric that represents the average length of time a customer is without service due to weather, maintenance, equipment failure and other factors.
After posting a SAIDI of about 103 minutes in 2017, we improved our scores in 2018 and 2019 to about 48 and 58 minutes, respectively. In 2020, despite record heat that placed constant stress on our infrastructure and equipment, we achieved a SAIDI of 43 minutes.
Although our SAIDI score did increase in 2021 to about 48 minutes due to variable summer monsoon activity, a comparison of 3-year average SAIDI scores shows overall improvement from a 2016-2018 value of 71 minutes to a 2019-2021 value of 50 minutes.
Continual maintenance and key prevention programs helped us achieve high reliability in recent years.
“We follow rigorous maintenance practices while continuing to strengthen the grid and ensuring future reliability for customers,” said Roberto Guevara, Director of Gas, Electric and Operational Excellence for UniSource. “Our commitment to delivering reliable service to customers shows in our consistently high SAIDI scores.”
UniSource uses several methods to assess needed distribution improvements. Our engineers evaluate distribution circuits based on reliability, demand, and other factors to help prioritize work and identify areas that need to be patrolled by journeyman linemen, who also identify maintenance needs. At our substations, we continually evaluate the condition of equipment using time-based inspections and online monitors to help determine maintenance, testing, or replacement needs.
Other improvements to transmission lines, substations and communication systems have supported the integration of renewable resources while helping us better serve customers’ energy needs.
“Our continuing efforts over the last several years have resulted in a more resilient system and reliable service for customers,” Guevara said.