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Rate And Regulatory Matters | 9 Months Ended
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Sep. 30, 2025
Public Utilities, General Disclosures [Abstract] |
RATE AND REGULATORY MATTERS | RATE AND REGULATORY MATTERS Below is a summary of updates to significant regulatory proceedings and related legal proceedings. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of the Form 10-K for additional information and a summary of our regulatory frameworks. We are unable to predict the ultimate outcome of these matters, the timing of final decisions of the various agencies and courts, or the impact on our results of operations, financial position, or liquidity. Missouri Missouri Senate Bill 4 In April 2025, Missouri Senate Bill 4 was enacted and became effective in August 2025. The law includes certain provisions that affect the regulation of Ameren Missouri’s electric and natural gas businesses. These provisions create modifications to the PISA and integrated resource planning, require electric utilities to submit service tariff schedules for high-demand customers, allow the MoPSC to authorize inclusion of construction work in progress in rate base for new natural gas-fired generation facilities and new generation facilities approved through integrated resource planning, and allow natural gas utilities to file regulatory rate reviews using a future test year, among other things. Pursuant to the law, the PISA has been modified to include new natural gas generating units placed in service after the effective date of the law as qualifying property, plant, and equipment eligible for deferral and recovery of 85% of the related depreciation expense. These new natural gas generating units will also be included in the 85% of rate base allowed to earn a return at the applicable WACC under the PISA. The law also reduced the annual limit on increases to the electric service revenue requirement used to set customer rates, compared to the revenue requirement established in the immediately preceding rate order, due to the inclusion of incremental PISA deferrals in the revenue requirement. The annual limit in effect was 2.5% and changed to 2.25%, prorated monthly, for revenue requirements approved by the MoPSC after August 2025. Furthermore, the PISA's effective date has been extended through 2035, unless Ameren Missouri requests and receives MoPSC approval of an extension through 2040. The law also requires an electric utility to develop and submit to the MoPSC schedules that include its service tariff applicable to customers projected to have 100 MWs or more of demand. These schedules must reasonably ensure that such high-demand customers’ rates reflect a representative share of the costs incurred to serve them and further, must prevent other lower-demand customer rates from reflecting any unjust or unreasonable costs arising from service provided to these high-demand customers. In addition, the law made modifications to integrated resource planning, which requires Missouri electric utilities to file plans for meeting their customers' long-term energy needs. By August 2027, the MoPSC will publish a schedule for Missouri electric utilities to file integrated resource plans every four years. The MoPSC will be required to issue an order on the plans and shall determine whether the electric utility has submitted sufficient documentation and selected preferred resource plans representing a reasonable and prudent means of serving the utility's load obligations at just and reasonable rates. In making this determination, the MoPSC shall consider whether the plans appropriately balance specific factors described in the law. If the MoPSC approves the plans, requests for CCNs for new generation facilities to be constructed or acquired as a part of the approved plans shall be deemed necessary and convenient and the scope of the CCN proceedings to review projects will be limited. The approved generation facilities will also be eligible to include construction work in progress in rate base, subject to MoPSC approval, which would improve the timeliness of cash recovery. Utilities are not allowed to capitalize allowance for funds used during construction on amounts included in rate base under this provision. The amount of construction work in progress to be included in rate base is limited to prudently incurred expenditures made within the construction period for the facility. Further, outside of the integrated resource planning process discussed above, the law allows a Missouri electric utility to request that the MoPSC authorize the inclusion of construction work in progress for new natural gas-fired generation facilities in rate base. Under this provision, utilities are not allowed to capitalize allowance for funds used during construction on projects approved to include construction work in progress in rate base. The amount of construction work in progress to be included in rate base is limited to prudently incurred expenditures made within the construction period for the facility. The provisions allowing for the inclusion of construction work in progress on natural gas-fired generation in rate base expire in December 2035, unless Ameren Missouri requests and receives MoPSC approval of an extension through 2045. Also, beginning in July 2026 the law allows natural gas utilities to file regulatory rate reviews using a future test year, subject to MoPSC approval. If a natural gas utility is allowed to use a future test year, a reconciliation of the actual rate base and certain forecasted costs will be performed 45 days after the end of the test year. If a given year’s actual revenue requirement is less than the revenue requirement approved by the MoPSC due to changes in rate base or certain other costs, an adjustment is made to reduce natural gas operating revenues with an offset to a regulatory liability to reflect that test year’s amounts. The regulatory liability will then be refunded to customers in the next regulatory rate review and will accrue carrying costs at the applicable WACC. April 2025 MoPSC Electric Rate Order In April 2025, the MoPSC issued an order in Ameren Missouri’s 2024 electric service regulatory rate review, approving nonunanimous stipulations and agreements. The order authorizes an increase of $355 million to Ameren Missouri’s annual revenue requirement for electric retail service, effective June 1, 2025. The approved revenue requirement was based on infrastructure investments as of December 31, 2024. The order did not explicitly specify an ROE, capital structure, rate base, or any rate base disallowances. The order provides for the continued use of all existing riders and trackers. The order also changed annualized depreciation, regulatory asset and liability amortization amounts, and the base level of expenses for trackers. On an annualized basis, these changes reflect an increase in “Depreciation and amortization” of approximately $70 million, among other expense changes, on Ameren’s and Ameren Missouri’s consolidated statements of income. 2024 Natural Gas Delivery Service Regulatory Rate Order In July 2025, the MoPSC issued an order in Ameren Missouri’s 2024 natural gas delivery service regulatory rate review, approving a unanimous stipulation and agreement. The order authorizes an increase of $32 million to Ameren Missouri’s annual revenue requirement for natural gas delivery service, effective September 1, 2025. The order did not explicitly specify an ROE, capital structure, rate base, or any rate base disallowances. The order provides for the continued use of all of Ameren Missouri’s existing riders and trackers. Large Load Customer Rate Plan In November 2025, Ameren Missouri updated its May 2025 request with the MoPSC to modify its existing large primary service tariff to require customers requesting 75 MWs or more of demand and who are served at transmission level voltage to comply with additional tariff terms. The additional terms include a service term of 12 years plus a ramp period of up to five years to reach peak demand, minimum demand charges of 80% of contracted capacity, customer exit terms and fees, and customer credit and collateral requirements, among other terms. In addition, new customer programs would be available under this tariff, which allow customers to support renewable generation, battery storage, and/or nuclear generation through incremental payments. A decision by the MoPSC is expected by February 2026. Generation and Storage Facilities Ameren Missouri is party to agreements to acquire and/or construct various generation and storage facilities that are consistent with the 2025 Change to the 2023 PRP. The generation and storage facilities are eligible for recovery under the PISA. The following table provides information with respect to each facility:
| Agreement type | Facility size | Status of MoPSC CCN |  | In-service date(a)
Vandalia Solar Project(b) | Self-build | 50-MW | Approved March 2024 |  | Fourth quarter 2025
Bowling Green Solar Project(b) | Self-build | 50-MW | Approved March 2024 |  | First quarter 2026
Split Rail Solar Project(b) | Build-transfer(c) | 300-MW | Approved March 2024 |  | Mid-2026
Castle Bluff Natural Gas Project(d) | Self-build | 800-MW | Approved October 2024 |  | Fourth quarter 2027
Big Hollow Battery Energy Storage Project | Self-build | 400-MW | Filed June 2025(e) |  | Second quarter 2028
Big Hollow Natural Gas Project | Self-build | 800-MW | Filed June 2025(e) |  | Third quarter 2028
Reform Solar Project | Self-build | 250-MW | Filed August 2025(e) |  | Fourth quarter 2028
(a)In-service dates are dependent on the timing of regulatory approvals and construction completion, among other things. (b)These projects collectively represent approximately $0.8 billion of capital expenditures. (c)FERC approval of acquisition received November 2024. (d)This project represents approximately $0.9 billion of capital expenditures. (e)Ameren Missouri expects a decision by the MoPSC in the first half of 2026. MISO Long-Range Transmission Projects CCN In 2022, the MISO approved the first tranche of projects related to a preliminary long-range transmission planning roadmap of projects through 2039. A portion of these projects were assigned or awarded via a competitive bid process to various utilities, including Ameren. In 2024, ATXI filed requests for CCNs, among other things, with the MoPSC related to the MISO long-range transmission projects that it expects to construct within the MoPSC’s jurisdiction. In July 2025, the MoPSC issued an order approving a CCN for a portion of the projects and a decision on the remaining projects is expected in 2025. Illinois MYRP In December 2024, the ICC issued an order in connection with a revised Grid Plan and a revised MYRP filed by Ameren Illinois in March 2024, approving revenue requirements for electric distribution services for 2024 through 2027 of $1,206 million, $1,287 million, $1,367 million, and $1,421 million, respectively. Using the 2023 revenue requirement as a starting point, the approved revenue requirements in the ICC’s December 2024 order represent a cumulative four-year increase of $308 million. Rate changes consistent with the December 2024 order became effective in December 2024. In March 2025, Ameren Illinois filed an appeal of the ICC’s December 2024 order to the Illinois Appellate Court for the Fifth Judicial District to revise the allowed ROE and to include an asset associated with other postretirement benefits in the rate base, among other things. In addition, Ameren Illinois filed an appeal related to orders issued by the ICC in December 2023 and June 2024 related to the MYRP proceeding. The appellate court is under no deadline to address the appeals, and Ameren Illinois cannot predict the ultimate outcome of the appeals. 2024 Electric Distribution Service Revenue Requirement Reconciliation Adjustment In April 2025, Ameren Illinois filed for a reconciliation adjustment to its 2024 electric distribution service revenue requirement with the ICC. In September 2025, Ameren Illinois filed a revised reconciliation adjustment, requesting recovery of $60 million. The adjustment reflects Ameren Illinois’ actual 2024 recoverable costs, 2024 year-end rate base, and a capital structure composed of 50% common equity. In September 2025, the ICC staff submitted its calculation of the reconciliation adjustment, recommending recovery of $47 million. The ICC staff’s recommendation excluded an asset associated with other postretirement benefits from the rate base. An ICC decision in this proceeding is required by December 2025, and any approved adjustment would be collected from customers in 2026. Electric Customer Energy-Efficiency Investments In May 2025, Ameren Illinois filed its annual electric energy-efficiency formula rate update to increase its annual revenues by $12 million with the ICC. In August 2025, the ICC staff filed a recommendation supporting Ameren Illinois’ requested increase. An ICC decision in this proceeding is required by December 2025, with new rates effective in January 2026. Electric Energy Efficiency Plan In August 2025, the ICC issued an order approving Ameren Illinois’ energy-efficiency plan that includes annual investments in electric energy-efficiency programs of approximately $126 million per year from 2026 through 2029. The ICC has the ability to reduce the amount of electric energy-efficiency savings goals in future program years if there are insufficient cost-effective programs available, which could reduce the investments in electric energy-efficiency programs. 2025 Natural Gas Delivery Service Rate Review In January 2025, Ameren Illinois filed a request with the ICC seeking approval to increase its annual revenues for natural gas delivery service. In July 2025, Ameren Illinois filed a revised request seeking to increase its annual revenues by $135 million. The request is based on a 10.7% ROE, a capital structure composed of 52% common equity, and a rate base of $3.3 billion. Ameren Illinois used a 2026 future test year in this proceeding. In August 2025, the ICC staff filed a revised recommendation to increase Ameren Illinois’ annual revenues for natural gas delivery service by $104 million. The recommendation is based on a 9.93% ROE, a capital structure composed of 50% common equity, and a rate base of $3.2 billion. In addition, in August 2025, the Illinois Attorney General's office recommended an increase to annual revenues for natural gas delivery service of $55 million, based on a 9.45% ROE, a capital structure composed of 50% common equity, and a rate base of $3.0 billion. In October 2025, the administrative law judge issued a proposed order for an increase to annual revenues of $91 million. The order was consistent with the ICC staff’s recommendation with the exception of the exclusion of the non-service cost component of the net periodic benefit income related to other postretirement benefits in the annual revenue requirement. A decision by the ICC in this proceeding is required by early December 2025, with new rates expected to be effective in early December 2025. Ameren Illinois cannot predict the level of any delivery service rate change the ICC may approve, nor whether any rate change that may eventually be approved will be sufficient to enable Ameren Illinois to recover its costs and to earn a reasonable return on investments when the rate changes go into effect. MISO Long-Range Transmission Projects CCN In 2022, the MISO approved the first tranche of projects related to a preliminary long-range transmission planning roadmap of projects through 2039. A portion of these projects were assigned or awarded via a competitive bidding process to various utilities, including Ameren. In July 2025, the ICC issued an order approving a request filed by Ameren Illinois and ATXI for a CCN, among other things, related to the portion of the MISO long-range transmission projects they will construct within the ICC’s jurisdiction. Federal MISO Transmission Rate Incentives In 2024, the MISO approved a first set of second tranche projects related to its preliminary long-range transmission planning roadmap of projects through 2039. A portion of these projects were assigned to Ameren and are estimated to cost approximately $1.3 billion, based on the MISO’s cost estimate. In July 2025, the FERC approved transmission rate incentives relating to the second tranche projects assigned to Ameren. The incentives will allow construction work in progress to be included in rate base for projects constructed by ATXI, thereby improving the timeliness of cash recovery, and would allow recovery of prudently incurred costs, subject to FERC approval, for any portion of the projects if they are abandoned for reasons beyond the control of Ameren. ATXI will not capitalize allowance for funds used during construction on the related projects. FERC ROE Complaint Cases Since November 2013, the allowed base ROE for FERC-regulated transmission rate base under the MISO tariff has been subject to customer complaint cases and has been changed by various FERC orders. In October 2024, the FERC issued an order, which decreased the allowed base ROE from 10.02% to 9.98% and required refunds, with interest, for the periods from November 2013 to February 2015 and from late September 2016 forward. In January 2025, the MISO transmission owners, including Ameren Missouri, Ameren Illinois, and ATXI, filed an appeal of the October 2024 order to the United States Court of Appeals for the District of Columbia Circuit. In March 2025, the FERC issued an order rejecting all rehearing requests of the October 2024 order. In April 2025, the MISO transmission owners, including Ameren Missouri, Ameren Illinois, and ATXI, filed an appeal of the March 2025 order to the United States Court of Appeals for the District of Columbia Circuit. As of September 30, 2025, Ameren and Ameren Illinois had recorded liabilities in "Current regulatory liabilities" on their balance sheets of $7 million and $4 million, respectively, to reflect the expected refunds, including interest, associated with the allowed base ROE set by the October 2024 order.

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