IUB approves Alliant’s request to reconsider Duane Arnold Solar advance ratemaking principles

Iowa Utilities Board had asked Alliant to file information to meet Iowa law requirements

The Iowa Utilities Board on Thursday approved advance ratemaking principles for the Duane Arnold Solar I and II projects requested by Alliant Energy subsidiary Interstate Power and Light Company.

The order reverses the IUB’s order Nov. 9, 2022, which found Alliant had not met the statutory minimums for receiving advance ratemaking principles for Duane Arnold I and II, a battery storage facility, and an additional 200 megawatts of solar generation.

The IUB granted reconsideration of the November 9, 2022 order for Duane Arnold I and II, but not for the battery storage and extra solar generation projects, in an order issued Dec 29, 2022.

The IUB said in a release Thursday that Alliant had provided the information necessary to meet the statutory requirements. Iowa Code section 476.53 requires the IUB to approve advance ratemaking principles for renewable generation facilities once the utility has met the statutory requirements.

Requests for advance ratemaking principles enable utilities to establish regulatory treatment for certain aspects of electric generation facilities in advance of construction, but such cases do not immediately impact customers’ electrical base rates. If the utility proceeds with construction, a contested rate case must still be filed with the IUB once the new generation source is placed into service.

Thursday’s order approves five principles for Duane Arnold I and II; denies Alliant’s request for a limited energy adjustment clause (EAC) waiver; denies a return on equity for the projects, leaving that issue to be addressed in Alliant’s next general customer rate case; and does not approve a principle that would have excluded benefits from being shared with ratepayers until Duane Arnold I and II costs are recovered in rates.

Alliant has 30 days to accept the advance ratemaking principles approved in Thursday’s order.

Under Iowa Code, a rate-regulated public utility can seek advance ratemaking principles when it intends to construct (or acquire) an electric power generating facility to help serve its customer base with a nameplate capacity of at least 300 megawatts, a combined-cycle electric power generating facility, or an alternate energy production facility.

Alliant filed its application for advance ratemaking principles for the Duane Arnold Solar I and II projects Nov. 2, 2021, in IUB Docket No. RPU-2021-0003.