Electric Reliability Measure Exceeds Goal

Published on December 06, 2023

Chart of SAIDI comparisons

In November, the Los Alamos Department of Public Utilities (DPU) exceeded a goal for electric reliability that felt unreachable in the not-too-distant past.

The DPU uses the SAIDI, short for System Average Interruption Duration Index, as a measure of reliability. Simply put, it is a calculation of the average amount of time that an electric customer can expect to be without power per year, and the lower the number, the better. A rolling average that is recalculated monthly, the DPU has a long-standing goal of 60 minutes.

At the end of November, DPU’s SAIDI dropped to 31 minutes. A year ago, DPU’s SAIDI was at 220 minutes and for the same month in 2021, it was at 90. For purposes of comparison, an annual SAIDI for both the state of New Mexico and the whole country (excluding territories) is published by the Energy Information Administration. For New Mexico, the SAIDI is 175 minutes, and for the United States, it is 333 minutes.

“We have aimed to keep our SAIDI below 60 for many years and it’s been up and down,” said Deputy Utility Manager Stephen Marez. “It’s a constantly moving measure, but when it gets as low as 31, it’s not a bad time to celebrate.”

The calculation to determine DPU’s SAIDI considers outages that occur on DPU’s electric system, the number of customers affected, the number of customers on the total system, and the number of minutes that span each outage. DPU works to increase reliability through underground and overhead infrastructure replacements and through an aggressive tree trimming program.