Supplemental Information (Tables)

12 Months Ended

Dec. 31, 2024

Supplemental Information [Abstract]

Schedule of Cash and Cash Equivalents Including Restricted Cash

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the balance sheets and the statements of cash flows as of December 31, 2024 and 2023:

	December 31, 2024						December 31, 2023
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
“Cash and cash equivalents”	$	7	$	—	$	—	$	25	$	—	$	—
Restricted cash included in “Other current assets”	15		7		6		13		5		5
Restricted cash included in “Other assets”	296		—		296		229		—		229
Restricted cash included in “Nuclear decommissioning trust fund”	10		10		—		5		5		—
Total cash, cash equivalents, and restricted cash	$	328	$	17	$	302	$	272	$	10	$	234

Schedule of Accounts, Notes, Loans and Financing Receivable

The following table provides a reconciliation of the beginning and ending amount of the allowance for doubtful accounts for the years ended December 31, 2024 and 2023:

	December 31, 2024						December 31, 2023
	Ameren Missouri		Ameren Illinois(a)		Ameren		Ameren Missouri		Ameren Illinois(a)		Ameren
Beginning balance at January 1	$	12	$	18	$	30	$	13	$	18	$	31
Bad debt expense	11		28		39		11		40		51
Charged to other accounts(b)	—		8		8		—		5		5
Net write-offs	(11)		(36)		(47)		(12)		(45)		(57)
Ending balance at December 31	$	12	$	18	$	30	$	12	$	18	$	30

(a)Ameren Illinois has rate-adjustment mechanisms that allow it to recover the difference between its actual net bad debt write-offs under GAAP, including those associated with receivables purchased from alternative retail electric suppliers, and the amount of net bad debt write-offs included in its base rates.

(b)Amounts associated with the allowance for doubtful accounts related to receivables purchased by Ameren Illinois from alternative retail electric suppliers, as required by the Illinois Public Utilities Act.

Schedule of Supplemental Balance Sheet Information Related to Operating Leases

The following table provides supplemental balance sheet information related to operating leases as of December 31, 2024:

	Ameren			Ameren Missouri
Other assets	$	72		$	69
Other current liabilities	5			4
Other deferred credits and liabilities	67			65
Weighted average remaining operating lease term	29 years			30 years
Weighted average discount rate(a)	5.3		%	5.3		%

(a)As an implicit rate is not readily determinable under most of our lease agreements, we use our incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. We use an implicit rate when readily determinable.

Schedule of Maturity of Operating Lease Liabilities

The following table presents Ameren’s and Ameren Missouri’s remaining maturities of operating lease liabilities as of December 31, 2024:

	Ameren		Ameren Missouri
2025	$	8	$	7
2026	5		4
2027	4		3
2028	4		4
2029	4		4
Thereafter	131		131
Total lease payments	$	156	$	153
Less imputed interest	84		84
Total	$	72	$	69

Schedule of Inventories

The following table presents the components of inventories for each of the Ameren Companies at December 31, 2024 and 2023:

	December 31, 2024						December 31, 2023
	Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois		Ameren
Fuel(a)	$	113	$	—	$	113	$	109	$	—	$	109
Natural gas stored underground	9		82		91		8		87		95
Materials, supplies, and other	392		162		558		391		138		529
Total inventories	$	514	$	244	$	762	$	508	$	225	$	733

(a)Consists of coal, oil, and propane.

Schedule of Asset Retirement Obligations

The following table provides a reconciliation of the beginning and ending carrying amount of AROs for the years ended December 31, 2024 and 2023:

	December 31, 2024									December 31, 2023
	Ameren Missouri			Ameren Illinois			Ameren			Ameren Missouri			Ameren Illinois			Ameren
Beginning balance at January 1	$	787	(a)	$	4	(b)	$	791	(a)	$	782		$	4		$	786
Liabilities incurred	21		(c)	—			21		(c)	—			—			—
Liabilities settled	(13)			—			(13)			(10)			—			(10)
Accretion(d)	35		(d)	—			35		(d)	33			—			33
Change in estimates	(7)			—			(7)			(18)			—			(18)
Ending balance at December 31	$	823	(a)(e)	$	4	(b)	$	827	(a)(e)	$	787	(a)	$	4	(b)	$	791	(a)

(a)Balance included $5 million and $19 million in “Other current liabilities” on the balance sheet as of December 31, 2024 and 2023, respectively.

(b)Included in “Other deferred credits and liabilities” on the balance sheet.

(c)In 2024, Ameren and Ameren Missouri recorded an ARO related to decommissioning for the Cass County, Boomtown, and Huck Finn energy centers. In addition, as a result of the 2024 CCR Rule, Ameren and Ameren Missouri recorded an increase to their AROs associated with CCR storage facilities. See Note 14 – Commitments and Contingencies for additional information.

(d)Accretion expense attributable to Ameren Missouri was recorded as a decrease to regulatory liabilities.

(e)The balance as of December 31, 2024, included an ARO related to the decommissioning of the Callaway Enter Center of $648 million.

Schedule of Excise Taxes

The following table presents the excise taxes recorded on a gross basis in “Operating Revenues – Electric,” “Operating Revenues – Natural gas” and “Operating Expenses – Taxes other than income taxes” on the statements of income for the years ended December 31, 2024, 2023, and 2022:

	2024		2023		2022
Ameren Missouri	$	169	$	166	$	162
Ameren Illinois	130		121		133
Ameren	$	299	$	287	$	295

Schedule of Rates and Amounts For Allowance for Funds Used During Construction

The following table presents the average rate that was applied to eligible construction work in progress and the amounts of allowance for funds used during construction capitalized in 2024, 2023, and 2022:

	2024			2023			2022
Average rate:
Ameren Missouri	6		%	6		%	5		%
Ameren Illinois	6		%	6		%	5		%
Ameren:
Allowance for equity funds used during construction	$	76		$	54		$	43
Allowance for borrowed funds used during construction	56			48			26
Total Ameren	$	132		$	102		$	69
Ameren Missouri:
Allowance for equity funds used during construction	$	58		$	30		$	24
Allowance for borrowed funds used during construction	39			27			13
Total Ameren Missouri	$	97		$	57		$	37
Ameren Illinois:
Allowance for equity funds used during construction	$	17		$	19		$	18
Allowance for borrowed funds used during construction	15			17			12
Total Ameren Illinois	$	32		$	36		$	30

Schedule of Earnings Per Share, Basic and Diluted

The following table reconciles the weighted-average number of common shares outstanding to the diluted weighted-average number of common shares outstanding for the years ended December 31, 2024, 2023, and 2022:

	2024	2023	2022
Weighted-average Common Shares Outstanding – Basic	266.8	262.8	258.4
Assumed settlement of performance share units and restricted stock units	0.5	0.6	1.0
Dilutive effect of forward sale agreements	0.1	—	0.1
Weighted-average Common Shares Outstanding – Diluted(a)	267.4	263.4	259.5

(a)There was an immaterial number of anti-dilutive securities excluded from the earnings per diluted share calculations for the years ended December 31, 2024, 2023, and 2022 related to performance share units and restricted stock units. Outstanding forward sale agreements as of December 31, 2024 that were anti-dilutive for the year ended December 31, 2024 were excluded from the earnings per diluted share calculation as calculated using the treasury stock method. The outstanding forward sale agreements as of December 31, 2023, were anti-dilutive for the year ended December 31, 2023, and excluded from the earnings per diluted share calculation as calculated using the treasury stock method. For additional information about the outstanding forward sale agreements, see Note 5 – Long-term Debt and Equity Financings.

Schedule of Cash Flow, Supplemental Disclosures

The following table provides noncash financing and investing activity excluded from the statements of cash flows for the years ended December 31, 2024, 2023, and 2022:

	December 31, 2024						December 31, 2023						December 31, 2022
	Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois
Investing
Accrued capital expenditures, including nuclear fuel expenditures	$	480	$	303	$	157	$	518	$	270	$	212	$	441	$	243	$	181
Net realized and unrealized gain (loss) – nuclear decommissioning trust fund	165		165		—		167		167		—		(218)		(218)		—
Return of investment in industrial development revenue bonds(a)	—		—		—		240		240		—		—		—		—
Financing
Issuance of common stock for stock-based compensation	$	16	$	—	$	—	$	40	$	—	$	—	$	31	$	—	$	—
Issuance of common stock under the DRPlus	7		—		—		7		—		—		8		—		—
Termination of a financing agreement(a)	—		—		—		240		240		—		—		—		—

(a)In January 2023, Ameren Missouri and Audrain County mutually agreed to terminate a financing obligation agreement related to the CT energy center in Audrain County, which was scheduled to expire in December 2023. No cash was exchanged in connection with the termination of the agreement as the $240 million principal amount of the financing obligation due from Ameren Missouri was equal to the amount of bond service payments due to Ameren Missouri.