Rate And Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2022

Public Utilities, General Disclosures [Abstract]

Schedule of Regulatory Frameworks and Significant Recovery Mechanisms

The following table presents the regulatory frameworks and significant regulatory recovery mechanisms for each of Ameren’s rate-regulated businesses, which are discussed in more detail below:

	Ameren Missouri	Ameren Illinois’ electric distribution business	Ameren Illinois’ natural gas delivery business	Ameren Illinois’ and ATXI’s electric transmission businesses
Regulatory framework	•Historical test year ratemaking •Natural gas revenues for residential customers adjusted for sales volume deviations resulting from weather through the WNAR	•Performance-based formula ratemaking(a) •Initial rates based on historical test year and expected net plant additions for the year before rates become effective •Revenues decoupled from sales volumes	•Future test year ratemaking •Revenues for residential and small nonresidential customers decoupled from sales volumes through the VBA	•Formula ratemaking •Initial rates based on future test year •Revenues decoupled from sales volumes
Regulatory mechanisms	•PISA Riders: •RESRAM •FAC •MEEIA •PGA •WNAR Trackers: •Pension and postretirement benefit costs •Certain excess deferred income taxes •Renewable energy standard costs •Property taxes	•Electric distribution service and energy-efficiency revenue requirement reconciliation adjustments Riders: •Power procurement •Transmission services •Renewable energy credit compliance •Zero emission credits •Certain environmental costs •Bad debt write-offs •Costs of certain asbestos-related claims	Riders: •QIP(b) •PGA •VBA •Energy-efficiency program costs •Certain environmental costs •Bad debt write-offs •Invested capital taxes	•Revenue requirement reconciliation adjustment

(a)Ameren Illinois used the IEIMA performance-based formula ratemaking framework to establish annual electric distribution customer rates effective through 2023. In January 2023, Ameren Illinois filed an MYRP to establish rates effective beginning in 2024. See below for additional information regarding the MYRP filed in January 2023.

(b)Without legislative action, the QIP will expire after December 2023.

Schedule of Solar Projects

The following table provides information with respect to each build-transfer agreement:

	Boomtown Solar Project	Huck Finn Solar Project
Agreement date	February 2022	June 2022
Facility size	150-MW	200-MW
Location	Southeastern Illinois	Central Missouri
Status of MoPSC certificate of convenience and necessity	Requested in July 2022(a)	Approved February 2023(b)
Status of FERC approval of acquisition	Expect to request by mid-2023	Requested in November 2022
Expected completion date(c)	As early as fourth quarter 2024	As early as fourth quarter 2024

(a)In December 2022, the MoPSC staff filed a recommendation that the MoPSC should not approve Ameren Missouri’s request for a certificate of convenience and necessity for the Boomtown Solar Project, arguing Ameren Missouri did not adequately demonstrate the facility is needed to continue providing service to customers. Ameren Missouri expects a decision by the MoPSC by April 2023.

(b)In February 2023, the MoPSC issued an order approving a nonunanimous stipulation and agreement regarding a requested certificate of convenience and necessity for the Huck Finn Solar Project.

(c)The expected completion dates may be impacted by the timing of regulatory approvals and potential sourcing issues resulting from a United States Department of Commerce investigation of solar panel components imported from four Southeast Asian countries initiated in late March 2022 and the detention of certain solar panel components sourced from China as a result of the Uyghur Forced Labor Prevention Act that became effective in June 2022.

Schedule of MYRP details

The following table includes the forecasted revenue requirement, the requested ROE, the requested capital structure common equity percentage, and the forecasted average annual rate base for 2024 through 2027, as reflected in Ameren Illinois’ MYRP:

Year	Forecasted Revenue Requirement (in millions)	Requested ROE	Requested Capital Structure Common Equity Percentage(a)	Forecasted Average Annual Rate Base (in billions)
2024	$1,282	10.5%	53.99%	$4.3
2025	$1,373	10.5%	53.97%	$4.6
2026	$1,477	10.5%	54.02%	$5.0
2027	$1,556	10.5%	54.03%	$5.3

(a)A capital structure of up to and including 50% common equity is deemed prudent and reasonable by law. A higher equity ratio requires specific ICC approval.

Schedule Of Regulatory Assets And Liabilities

The following table presents our regulatory assets and regulatory liabilities at December 31, 2022 and 2021:

	2022						2021
	Ameren Missouri		Ameren Illinois		Ameren		Ameren Missouri		Ameren Illinois		Ameren
Regulatory assets:
Under-recovered FAC(a)	$	140	$	—	$	140	$	47	$	—	$	47
Under-recovered Illinois electric power costs(b)	—		33		33		—		3		3
Under-recovered PGA(b)(c)	23		—		23		49		114		163
MTM derivative losses(d)	68		68		136		77		125		202
IEIMA revenue requirement reconciliation adjustment(e)(f)	—		134		134		—		42		42
FERC revenue requirement reconciliation adjustment(g)	—		11		33		—		18		43
Under-recovered VBA(h)	—		—		—		—		17		17
Income taxes(i)	111		72		185		115		69		185
Callaway refueling and maintenance outage costs(j)	33		—		33		14		—		14
Unamortized loss on reacquired debt(k)	47		7		54		50		13		63
Environmental cost riders(l)	—		64		64		—		70		70
Storm costs(f)(m)	—		14		14		—		17		17
Allowance for funds used during construction for pollution control equipment(f)(n)	11		—		11		13		—		13
Customer generation rebate program(f)(o)	—		50		50		—		47		47
PISA(f)(p)	320		—		320		244		—		244
Certain Meramec Energy Center costs(q)	51		—		51		—		—		—
FEJA energy-efficiency rider(f)(r)	—		416		416		—		350		350
Other	44		39		83		41		47		88
Total regulatory assets	$	848	$	908	$	1,780	$	650	$	932	$	1,608
Less: current regulatory assets	(254)		(87)		(354)		(127)		(180)		(319)
Noncurrent regulatory assets	$	594	$	821	$	1,426	$	523	$	752	$	1,289
Regulatory liabilities:
Over-recovered FAC(a)	$	4	$	—	$	4	$	19	$	—	$	19
Over-recovered Illinois electric power costs(b)	—		—		—		—		13		13
Over-recovered PGA(b)	—		10		10		—		1		1
MTM derivative gains(d)	51		40		91		50		41		91
Income taxes(i)	1,095		749		1,931		1,208		770		2,066
Cost of removal(s)	1,064		989		2,091		1,028		929		1,988
AROs(t)	365		—		365		603		—		603
Bad debt rider(u)	—		21		21		—		19		19
Pension and postretirement benefit costs(v)	242		162		404		399		392		791
Pension and postretirement benefit costs tracker(w)	60		—		60		28		—		28
Renewable energy credits and zero emission credits(x)	—		373		373		—		246		246
RESRAM(y)	2		—		2		19		—		19
Excess income taxes collected in 2018(z)	7		—		7		25		—		25
Other	51		33		86		32		17		52
Total regulatory liabilities	$	2,941	$	2,377	$	5,445	$	3,411	$	2,428	$	5,961
Less: current regulatory liabilities	(70)		(64)		(136)		(57)		(54)		$	(113)
Noncurrent regulatory liabilities	$	2,871	$	2,313	$	5,309	$	3,354	$	2,374	$	5,848

(a)Under-recovered or over-recovered fuel costs to be recovered or refunded through the FAC. Specific accumulation periods aggregate the under-recovered or over-recovered costs over four months, any related adjustments that occur over the following four months, and the recovery from, or refund to, customers that occurs over the next eight months.

(b)Under-recovered or over-recovered costs from utility customers. Amounts will be recovered from, or refunded to, customers within one year of the deferral.

(c)As a result of the significant increase in customer demand and prices for natural gas and electricity experienced in mid-February 2021 due to extremely cold weather, for the month of February 2021, Ameren Missouri and Ameren Illinois had under-recovered costs under their PGA clauses of $53 million and $221 million, respectively. Pursuant to an October 2021 MoPSC order, the collection period for Ameren Missouri’s cumulative PGA under-recovery as of August 2021, which includes the February 2021 under-recovery, was extended from 12 months to 36 months, beginning November 2021. Ameren Illinois collected its February 2021 PGA under-recovery over 18 months beginning April 2021.

(d)Deferral of commodity-related derivative MTM losses or gains. See Note 7 – Derivative Financial Instruments for additional information.

(e)The difference between Ameren Illinois’ electric distribution service annual revenue requirement calculated under the performance-based formula ratemaking framework and the revenue requirement included in customer rates for that year. Any under-recovery or over-recovery will be recovered from, or refunded to, customers with interest within two years.

(f)These assets earn a return at the applicable WACC.

(g)Ameren Illinois’ and ATXI’s annual revenue requirement reconciliation calculated pursuant to the FERC’s electric transmission formula ratemaking framework. Any under-recovery or over-recovery will be recovered from, or refunded to, customers within two years.

(h)Under-recovered natural gas revenue caused by sales volume deviations from weather normalized sales approved by the ICC in rate regulatory reviews. Each year’s amount will be recovered from customers from April through December of the following year.

(i)The regulatory assets represent amounts that will be recovered from customers for deferred income taxes related to the equity component of allowance for funds used during construction and the effects of tax rate increases. The regulatory liabilities represent amounts that will be refunded to customers for deferred income taxes related to depreciation differences, other tax liabilities, and the unamortized portion of investment tax credits recorded at rates in excess of current statutory rates. Amounts associated with the equity component of allowance for funds used during construction and the unamortized portion of investment tax credits will be amortized over the expected life of the related assets. For net regulatory liabilities related to deferred income taxes recorded at rates other than the current statutory rate, the weighted-average remaining amortization periods at Ameren, Ameren Missouri, and Ameren Illinois are 38, 31, and 44 years.

(j)Maintenance expenses related to scheduled refueling and maintenance outages at Ameren Missouri’s Callaway Energy Center. Amounts are amortized over the period between refueling and maintenance outages, which has historically been approximately 18 months.

(k)Losses related to reacquired debt. These amounts are being amortized over the lives of the related new debt issuances or the original lives of the old debt issuances if no new debt was issued.

(l)The recoverable portion of accrued environmental site liabilities that will be collected from electric and natural gas customers through ICC-approved cost recovery riders. The period of recovery will depend on the timing of remediation expenditures. See Note 14 – Commitments and Contingencies for additional information.

(m)Storm costs from 2020, 2021, and 2022 deferred in accordance with the IEIMA. These costs are being amortized over five-year periods beginning in the year the storm occurred.

(n)The MoPSC’s May 2010 electric rate order allowed Ameren Missouri to record an allowance for funds used during construction for pollution control equipment at its Sioux Energy Center until the cost of that equipment was included in customer rates beginning in 2011. These costs are being amortized over the expected life of the Sioux Energy Center, currently through 2028. Ameren Missouri’s electric rate increase request discussed above reflects extending the retirement date of the Sioux Energy Center from 2028 to 2030.

(o)Costs associated with Ameren Illinois’ customer generation rebate program. Costs are amortized over a 15-year period, beginning in the year rebates are paid.

(p)Under the PISA, Ameren Missouri is permitted to defer and recover 85% of the depreciation expense and earn a return at the applicable WACC on investments in certain property, plant, and equipment placed in service and not included in base rates. Accumulated PISA deferrals, which also earn a return at the applicable WACC, are added to rate base prospectively and amortized over a period of 20 years following a regulatory rate review.

(q)Certain costs associated with the Meramec Energy Center, which were authorized for recovery by the December 2021 MoPSC electric rate order discussed above. These costs are being collected over five years beginning in February 2022.

(r)The electric energy-efficiency investments are being amortized over their weighted-average useful lives beginning in the period in which they were made, with current remaining amortization periods ranging from four to 12 years.

(s)Estimated funds collected from customers to pay for the future removal cost of property, plant, and equipment retired from service, net of salvage.

(t)The ARO regulatory liability includes the nuclear decommissioning trust fund balance ($958 million and $1,159 million at December 31, 2022 and 2021, respectively), net of recoverable removal costs for AROs ($593 million and $556 million at December 31, 2022 and 2021, respectively). See Note 1 – Summary of Significant Accounting Policies – Asset Retirement Obligations.

(u)A rider for the difference between the level of bad debt write-offs, net of any subsequent recoveries, incurred by Ameren Illinois and the level of such costs included in electric distribution and natural gas delivery service rates. Under-recovered or over-recovered costs for each year are collected from, or refunded to, customers over a twelve-month period beginning June the following year.

(v)Over-recovered costs are being amortized in proportion to the recognition of prior service costs (credits) and actuarial losses (gains) attributable to Ameren’s pension plan and postretirement benefit plans. See Note 10 – Retirement Benefits for additional information.

(w)A regulatory recovery mechanism for the difference between the level of pension and postretirement benefit costs incurred by Ameren Missouri and the level of such costs included in customer rates. The period of refund varies based on MoPSC approval in a regulatory rate review. For costs incurred prior to 2022, the weighted-average remaining amortization period is four years. For costs incurred during 2022, the amortization period will be determined the 2022 electric service regulatory rate review discussed above.

(x)Funds collected for the purchase of renewable energy credits and zero emission credits through IPA procurements. The balance will be amortized as the credits are purchased.

(y)Over-recovered costs associated with Ameren Missouri’s compliance with the state of Missouri’s renewable energy standard. Under-recovered or over-recovered costs are aggregated over a twelve-month period beginning each August and are amortized over a twelve-month period beginning February the following year.

(z)The excess amount collected in rates related to the TCJA from January 1, 2018, through July 31, 2018. Pursuant to the December 2021 MoPSC electric rate order discussed above, the regulatory liability is being amortized over a 15-month period, which began in March 2022.