AMEREN CORP

We use the words “our,” “we” or “us” with respect to certain information that relates to Ameren, Ameren Missouri, and Ameren Illinois, collectively. When appropriate, subsidiaries of Ameren Corporation are named specifically as their various business activities are discussed.

2023 PRP – Preferred Resource Plan, a nonbinding plan that Ameren Missouri filed with the MoPSC in September 2023 that includes Ameren Missouri’s preferred plan for meeting customers’ projected long-term energy needs.

2025 Change to the 2023 PRP– A change to Ameren’s 2023 PRP expected to be filed with the MoPSC in February 2025 reflecting certain modifications to Ameren Missouri’s preferred plan for meeting customers’ projected long-term energy needs.

Ameren – Ameren Corporation and its subsidiaries on a consolidated basis. In references to financing activities, acquisition activities, or liquidity arrangements, Ameren is defined as Ameren Corporation, the parent.

Ameren Companies – Ameren Corporation, Ameren Missouri, and Ameren Illinois, collectively, which are individual registrants within the Ameren consolidated group.

Ameren Illinois– Ameren Illinois Company, an Ameren Corporation subsidiary that operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois, doing business as Ameren Illinois.

Ameren Illinois Electric Distribution– An Ameren Corporation and Ameren Illinois financial reporting segment consisting of the rate-regulated electric distribution business of Ameren Illinois.

Ameren Illinois Natural Gas – An Ameren Corporation and Ameren Illinois financial reporting segment consisting of the rate-regulated natural gas distribution business of Ameren Illinois.

Ameren Illinois Transmission – An Ameren Illinois financial reporting segment consisting of the rate-regulated electric transmission business of Ameren Illinois.

Ameren Missouri– Union Electric Company and its subsidiary, AMF, on a consolidated basis. Union Electric Company is an Ameren Corporation subsidiary that operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri, doing business as Ameren Missouri. Ameren Missouri is a financial reporting segment of Ameren Corporation.

Ameren Services – Ameren Services Company, an Ameren Corporation subsidiary that provides support services, such as accounting, legal, treasury, and asset management services, to Ameren (parent) and its subsidiaries.

Ameren Transmission– An Ameren Corporation financial reporting segment primarily consisting of the aggregated electric transmission businesses of Ameren Illinois and ATXI.

AMF– Ameren Missouri Securitization Funding I, LLC, a special purpose entity wholly owned by Ameren Missouri, was formed in 2024, for the purpose of issuing and servicing securitized utility tariff bonds related to Rush Island Energy Center retirement costs.

ARO – Asset retirement obligation.

ATM program – At-the-market equity distribution program.

ATXI – Ameren Transmission Company of Illinois, an Ameren Corporation subsidiary that operates a FERC rate-regulated electric transmission business in the MISO.

Baseload – The minimum amount of electric power delivered or required over a given period of time at a steady rate.

Base rate – The service rate charged to customers, which varies by segmentation within customer classes, excludes rates applicable to riders, and is determined by the ratemaking process used to establish the annual revenue requirement applicable to such service.

Btu – British thermal unit, a standard unit for measuring the quantity of heat energy required to raise the temperature of one pound of water by one degree Fahrenheit.

CCN – Certificate of convenience and necessity.

CCR – Coal combustion residuals, which include fly ash, bottom ash, boiler slag, and flue gas desulfurization materials generated from burning coal to generate electricity.

CCR Rule – Coal Combustion Residuals Rule, an EPA rule that established requirements for the disposal of CCR in landfills and surface impoundments, and the operation and closure of such landfills and surface impoundments.

CDP – A not-for-profit entity that administers a global disclosure system related to environmental matters, among other things.

CEJA – Climate and Equitable Jobs Act, an Illinois law that, among other things, gives Ameren Illinois the option to establish new electric distribution rates through either a traditional regulatory rate review, which may be based on a future test year, or an MYRP for a four-year period.

CO 2 – Carbon dioxide.

CODMs – Chief operating decision makers.

COLI– Company-owned life insurance.

Customer demand charges – Revenues from nonresidential customers based on their peak demand during a specified time interval.

Cooling degree days – The summation of positive differences between the average daily temperature and a 65-degree Fahrenheit base. This statistic is useful as an indicator of electricity demand by residential and commercial customers for summer cooling.

Credit Agreements – The Illinois Credit Agreement and the Missouri Credit Agreement, collectively.

CSAPR – Cross-State Air Pollution Rule, an EPA rule that requires states that contribute to air pollution in downwind states to limit air emissions from fossil-fuel-fired electric generating units.

CT – Combustion turbine, used primarily for peaking electric generation capacity.

Deferred payment arrangement – A payment option that allows certain Ameren Missouri and Ameren Illinois retail customers to pay a utility bill balance over an extended period of time, generally up to 12 months.

Dekatherm – A standard unit of energy equivalent to approximately one million Btus.

DOE – Department of Energy, a United States government agency.

DRPlus – Ameren Corporation’s dividend reinvestment and direct stock purchase plan.

EMANI – European Mutual Association for Nuclear Insurance.

EPA – Environmental Protection Agency, a United States government agency.

ERISA – Employee Retirement Income Security Act of 1974, as amended.

Excess deferred income taxes – Amounts resulting from the revaluation of deferred income taxes subject to regulatory ratemaking, which will be refunded to customers. Deferred income taxes are revalued when federal or state income tax rates decrease, and the offset to the revaluation of deferred income taxes subject to regulatory ratemaking is recorded to a regulatory liability.

Exchange Act – Securities Exchange Act of 1934, as amended.

FAC – Fuel adjustment clause, a fuel and purchased power rate-adjustment mechanism that allows Ameren Missouri to recover or refund, through customer rates, 95% of the variance in net energy costs from the amount set in base rates without a traditional regulatory rate review, subject to MoPSC prudence reviews.

FEJA– Future Energy Jobs Act, an Illinois law that allows Ameren Illinois to earn a return on its electric energy-efficiency investments, decouples electric distribution revenues from sales volumes, offers customer rebates for installing distributed generation, and includes extensions and modifications of certain IEIMA performance-based framework provisions, among other things. The decoupling provisions ensure that electric distribution revenues are not affected by changes in sales volumes, including those resulting from deviations from normal weather conditions.

FERC – Federal Energy Regulatory Commission, a United States government agency that regulates utility businesses and associated activities of holding and related service companies, including Ameren (parent), Ameren Missouri, Ameren Illinois, ATXI, and Ameren Services.

GAAP – Generally accepted accounting principles in the United States.

Grid Plan– Multi-year integrated grid plan, a plan required to be filed with the ICC every four years under the CEJA, which outlines how Ameren Illinois expects to invest in electric distribution infrastructure in order to support grid modernization, clean energy, energy efficiency, and the state of Illinois’ renewable energy, equity, climate, electrification, and environmental goals.

Heating degree days – The summation of negative differences between the average daily temperature and a 65-degree Fahrenheit base. This statistic is useful as an indicator of demand for electricity and natural gas for winter heating by residential and commercial customers.

ICC – Illinois Commerce Commission, a state agency that regulates Illinois utility businesses, including Ameren Illinois and ATXI.

IEIMA – Illinois Energy Infrastructure Modernization Act, an Illinois law that established a performance-based formula process for determining electric distribution service rates. Ameren Illinois established electric distribution rates through 2023 under this law.

Illinois Credit Agreement– Ameren’s and Ameren Illinois’ $1.2 billion senior unsecured credit agreement, which expires in December 2028, unless extended.

IPA – Illinois Power Agency, a state government agency that has broad authority to assist in the procurement of electric power for residential and small commercial customers.

IRA– The Inflation Reduction Act of 2022, federal legislation enacted in August 2022, which includes various provisions, such as expanded production and investment tax credits for clean energy investments, transferability of certain tax credits to an unrelated party for cash, and a corporate alternative minimum tax on certain entities, among other things.

IRS – Internal Revenue Service, a United States government agency.

Kilowatthour – A measure of electricity consumption equivalent to the use of 1,000 watts of power over one hour.

MATS – Mercury and Air Toxics Standards, an EPA rule that limits emissions of mercury and other air toxics from coal- and oil-fired electric generating units.

MEEIA – A rate-adjustment mechanism allowed under the Missouri Energy Efficiency Investment Act, a Missouri law that allows electric utilities to recover costs and performance incentives, if any, related to MoPSC-approved customer energy-efficiency and demand response programs without a traditional regulatory rate review, subject to MoPSC prudence reviews.

MEEIA 2019– Ameren Missouri’s portfolio of customer energy-efficiency and demand response programs, recovery of lost electric revenues, and performance incentives for March 2019 through December 2024, pursuant to Missouri law, as approved by the MoPSC in December 2018.

MEEIA 2025 – Ameren Missouri’s portfolio of customer energy-efficiency and demand response programs, recovery of lost electric revenues, and performance incentives for January 2025 through February 2028, pursuant to Missouri law, as approved by the MoPSC in November 2024.

MGP – Manufactured gas plant.

MISO – Midcontinent Independent System Operator, Inc., an RTO.

Missouri Credit Agreement– Ameren’s and Ameren Missouri’s $1.4 billion senior unsecured credit agreement, which expires in December 2028, unless extended.

Mmbtu – One million Btus.

Money pool – Borrowing agreements among Ameren and its subsidiaries to coordinate and provide for certain short-term cash and working capital requirements.

Moody’s – Moody’s Investors Service, Inc., a credit rating agency.

MoOPC – Missouri Office of Public Counsel.

MoPSC – Missouri Public Service Commission, a state agency that regulates Missouri utility businesses, including Ameren Missouri.

MRO – Midwest Reliability Organization, one of the regional electric reliability councils organized for coordinating the planning and operation of the United States’ bulk power supply.

MTM – Mark-to-market.

MW – Megawatt.

MWh – Megawatthour, one thousand kilowatthours.

MYRP – Multi-year rate plan, a four-year electric distribution service rate plan allowed to be filed with the ICC under the CEJA. Under a multi-year rate plan, the ICC approves base rates for electric distribution service charged to customers for each calendar year of a four-year period. Ameren Illinois reconciles its actual revenue requirement to the ICC-approved electric distribution service rates on an annual basis, subject to a reconciliation cap with exclusions for certain costs and riders, and adjustments to the ICC-determined ROE for performance incentives and penalties.

Native load – End-use retail customers whom Ameren Missouri or Ameren Illinois is obligated to serve by statute, franchise, contract, or other regulatory requirement.

NAV – Net asset value per share.

NEIL – Nuclear Electric Insurance Limited, which includes all of its affiliated companies.

NERC – North American Electric Reliability Corporation.

Net energy costs– Net energy costs, as defined in the FAC, which include fuel, fuel transportation, certain fuel additives, ash disposal costs and revenues, emission allowances, and purchased power costs, net of off-system sales and capacity revenues. Substantially all transmission revenues and charges are excluded from net energy costs. All off-system sales from the High Prairie and Atchison energy centers are excluded as those sales are included in the RESRAM.

Net metering– Net metering allows customers who generate their own electricity or subscribe to receive output from eligible facilities to feed electricity they do not use back into the grid. Customers receive a credit for the energy they add to the grid.

NOx – Nitrogen oxides.

NPNS – Normal purchases and normal sales.

NRC – Nuclear Regulatory Commission, a United States government agency that regulates commercial nuclear power plants and uses of nuclear materials.

NSPS – New Source Performance Standards, provisions under the Clean Air Act.

NSR – New Source Review provisions of the Clean Air Act, which include Nonattainment New Source Review and Prevention of Significant Deterioration regulations.

NYSE – New York Stock Exchange, LLC.

OCI – Other comprehensive income (loss) as defined by GAAP.

Off-system sales revenues– Revenues from other than native load sales, including wholesale sales.

PGA – Purchased gas adjustment tariffs, a rate-adjustment mechanism that permits prudently incurred natural gas costs to be recovered directly from utility customers without a traditional regulatory rate review, subject to regulatory prudence reviews.

PHMSA – Pipeline and Hazardous Materials Safety Administration, a United States government agency.

PISA – Plant-in-service accounting regulatory mechanism, a mechanism under Missouri law that permits electric utilities to defer and recover 85% of the depreciation expense and earn a return at the applicable WACC on rate base for certain property, plant, and equipment placed in service, and not included in base rates, subject to MoPSC prudence reviews. The rate base on which the return is calculated incorporates qualifying capital expenditures not included in base rates, as well as changes in total accumulated depreciation excluding retirements and plant-related deferred income taxes. The regulatory asset for accumulated PISA deferrals earns a return at the applicable WACC. The PISA is effective through 2028, unless Ameren Missouri requests and receives MoPSC approval of an extension through 2033.

QIP– Qualifying infrastructure plant, a rate-adjustment mechanism that provided Ameren Illinois’ natural gas business with recovery of, and a return on, qualifying infrastructure plant investments that were placed in service between regulatory rate reviews, subject to ICC prudence reviews. The QIP expired in December 2023.

Rate base– The basis on which a rate-regulated utility is permitted to earn a WACC. This basis is the net investment in assets used to provide utility service, which generally consists of in-service property, plant, and equipment, net of accumulated depreciation and accumulated deferred income taxes, inventories, and, depending on jurisdiction, construction work in progress.

RBA– Revenue balancing adjustment rider, a rate-adjustment mechanism for Ameren Illinois’ electric distribution business that decouples electric distribution revenues approved by the ICC from actual sales volumes and/or wholesale and miscellaneous revenue and allows Ameren Illinois to adjust electric distribution service rates charged to customers without an MYRP or a traditional regulatory rate review, subject to ICC prudence reviews. The rider ensures that Ameren Illinois’ electric distribution revenues are not affected by changes in sales volumes, including those resulting from deviations from normal weather conditions, or wholesale and miscellaneous revenues.

Regulatory lag – The exposure to differences in costs incurred and actual sales volumes as compared with the associated amounts included in customer rates. Rate increase requests in traditional regulatory rate reviews can take up to 11 months to be acted upon by the MoPSC and the ICC. As a result, revenue increases authorized by regulators will lag changing costs and sales volumes when based on historical periods.

RESRAM – Renewable energy standard rate-adjustment mechanism, a regulatory mechanism allowed under Missouri law that enables Ameren Missouri to recover costs relating to compliance with Missouri’s renewable energy standard, including recovery of investments in wind generation and other renewables, and earn a return at the applicable WACC on those investments not already provided for in customer rates or any other recovery mechanism by adjusting customer rates on an annual basis without a traditional regulatory rate review, subject to MoPSC prudence reviews. RESRAM regulatory assets earn carrying costs at short-term interest rates.

Revenue requirement – The cost of providing utility service to customers, which is calculated as the sum of a utility’s recoverable operating expenses, a return at the weighted-average cost of capital on rate base, and an amount for income taxes, based on the currently applicable statutory income tax rates and amortization associated with excess deferred income taxes.

RFP – Request for proposal.

Rider – A rate-adjustment mechanism that allows for the recovery, or refund, through customer rates of amounts specified by the mechanism without a traditional regulatory rate review.

ROE – Return on common equity.

RTO – Regional transmission organization.

S&P – S&P Global Ratings, a credit rating agency.

SEC – Securities and Exchange Commission, a United States government agency.

SERC – SERC Reliability Corporation, one of the regional electric reliability councils organized for coordinating the planning and operation ofthe United States’ bulk power supply.

Smart Energy Plan – Ameren Missouri’s plan to upgrade Missouri’s electric grid through at least 2029. Planned upgrades include investments to improve reliability and accommodate more renewable energy.

SO 2 – Sulfur dioxide.

STEM – Science, technology, engineering, and math.

TCJA – The Tax Cuts and Jobs Act of 2017, federal income tax legislation enacted in December 2017, which significantly changed the tax laws applicable to business entities. The TCJA includes specific provisions related to regulated public utilities.

Test year – The selected period of time, typically a 12-month period, for which a utility’s historical or forecasted operating results are used to determine the revenue requirement in a regulatory rate review.

Tracker – a regulatory recovery mechanism that allows for the deferral of differences between actual costs incurred and base level expenses included in customer rates as a regulatory asset or liability. The difference is included in base rates and recovered from, or refunded to, customers over a period of time as determined in a subsequent regulatory rate review.

TSR – Total shareholder return, the cumulative return of a common stock or index over a specified period of time assuming all dividends are reinvested.

VBA – Volume balancing adjustment, a rate-adjustment mechanism for Ameren Illinois’ natural gas business that decouples natural gas revenues from actual sales volumes and allows Ameren Illinois to adjust customer rates without a traditional regulatory rate review, subject to ICC prudence reviews. The rider ensures that Ameren Illinois’ natural gas revenues are not affected by changes in sales volumes, including those resulting from deviations from normal weather conditions, for residential and small nonresidential customers.

WACC– Weighted-average cost of capital, which is the weighted-average cost of debt and equity, as allowed by the applicable regulator.

WNAR– Weather normalization adjustment rider, a rate-adjustment mechanism that allows Ameren Missouri to adjust natural gas delivery service rates charged to residential customers without a traditional regulatory rate review, subject to MoPSC prudence reviews, when deviations from normal weather conditions cause natural gas revenues to vary from the related revenue requirement approved by the MoPSC in the previous regulatory rate review.

Zero emission credit – A credit that represents the environmental attributes of one MWh of energy produced from certain zero emissions nuclear-powered generation facilities, which certain Illinois utilities are required to purchase pursuant to the FEJA.