UniSource Energy Services is providing a credit to customers who may have been impacted by a billing error that affected some users of time-of-use (TOU), demand and demand time-of-use pricing plans.

After a recent upgrade, the software we use to log energy use occasionally applied off-peak usage to on-peak periods to some customers’ bills by mistake. This happened for seven weeks, from mid-December 2023 to early February 2024, until the error was identified and resolved.

Most customers were not affected by this error. After a thorough review of usage data, we determined that about 1,000 customers may have experienced discrepancies of about 1 percent from their regular usage.

As part of our commitment to accurate billing, we re-billed all potentially misbilled usage at our lower, off-peak rates and assumed a “zero” demand for those periods. This will result in a credit that, in most cases, will be less than $10 for residential customers.

UniSource is notifying affected residential customers through bill messages, emails and letters. We’re also contacting medium and large commercial customers impacted by this issue.

We’re committed to fair and accurate billing and apologize for any inconvenience this incident has caused. Affected customers will see the credit on their next bill.

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