Glendale staff: Grayson batteries near operation; tariff-refund process could return $10–15 million

Glendale Water and Power staff told the commission on June 1 that battery systems at the Grayson site have been installed on foundations, wired and are undergoing commissioning tests, and that the utility expects some or all of the system to enter commercial operation by the end of June.

“All are on their foundations. All are wired and all are being tested,” said Mr. Melon, who updated the commission on site progress and integration plans. He said the utility expects WZilla engines to be available by the end of July.

Melon also described ongoing work tied to recent tariff litigation affecting imported equipment. He said there is “a fair amount of chaos” around tariff definitions and that, as contracts are written, the contractor that owned the product when it crossed the border generally has the legal obligation to seek refunds. He said the utility may need to pay vendors up front and be paid back if contractors successfully recover duties.

When asked for an approximate dollar range, Melon said the staff estimate is “anywhere between 10 and 15 million.” The commission asked about how the refund flow would work; Melon said the refund path could be direct from federal authorities to the contractor and then to Glendale, or could pass through multiple subcontractor hands before reimbursing the utility.

Commissioners also discussed operational policy for battery depth-of-discharge and said staff will use a battery-management system and vendor monitoring (FlexGen) to coordinate operating parameters. Melon said the utility expects to avoid deep cycling routinely and will monitor charging and discharge behavior remotely.

No formal action was taken during the report; commissioners were invited to request follow-up details. Staff said they will return with clarifications about contractual responsibilities and any realized refund amounts as the contractor claims process advances.