The Iowa Utilities Board (IUB) today issued an order that approves advance ratemaking principles for two solar projects, Duane Arnold I and II, requested by Interstate Power and Light Company, a subsidiary of Alliant Energy (Alliant).

Today’s order reverses the IUB’s November 9, 2022, order that 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 other projects, in an order issued December 29, 2022. In today’s order, the IUB found 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.  

The 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 today’s order. 

Under Iowa Code 476.53, 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, or a combined-cycle electric power generating facility, or an alternate energy production facility.

Alliant filed its application for advance ratemaking principles on November 2, 2021, in Docket No. RPU-2021-0003.