Significant Accounting Policies (Policy)	12 Months Ended
Dec. 31, 2023
Significant Accounting Policies [Line Items]
Principles of Consolidation	Principles of Consolidation: CMS Energy and Consumers prepare their consolidated financial statements in conformity with GAAP. CMS Energy’s consolidated financial statements comprise CMS Energy, Consumers, NorthStar Clean Energy, and all other entities in which CMS Energy has a controlling financial interest or is the primary beneficiary. Consumers’ consolidated financial statements comprise Consumers and all other entities in which it has a controlling financial interest. CMS Energy uses the equity method of accounting for investments in companies and partnerships that are not consolidated, where they have significant influence over operations and financial policies but are not the primary beneficiary. CMS Energy and Consumers eliminate intercompany transactions and balances.
Use of Estimates	Use of Estimates: CMS Energy and Consumers are required to make estimates using assumptions that may affect reported amounts and disclosures. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents and Restricted Cash and Cash Equivalents: Cash and cash equivalents include short-term, highly liquid investments with original maturities of three months or less. Restricted cash and cash equivalents are held primarily for the repayment of securitization bonds and funds held in escrow. Cash and cash equivalents may also be restricted to pay other contractual obligations such as leasing of coal railcars. These amounts are classified as current assets since they relate to payments that could or will occur within one year.
Restricted Cash and Cash Equivalents	Cash and Cash Equivalents and Restricted Cash and Cash Equivalents: Cash and cash equivalents include short-term, highly liquid investments with original maturities of three months or less. Restricted cash and cash equivalents are held primarily for the repayment of securitization bonds and funds held in escrow. Cash and cash equivalents may also be restricted to pay other contractual obligations such as leasing of coal railcars. These amounts are classified as current assets since they relate to payments that could or will occur within one year.
Contingencies	Contingencies: CMS Energy and Consumers record estimated loss contingencies on their consolidated financial statements when it is probable that a loss has been incurred and when the amount of loss can be reasonably estimated. For environmental remediation projects in which the timing of estimated expenditures is considered reliably determinable, CMS Energy and Consumers record the liability at its net present value, using a discount rate equal to the interest rate on monetary assets that are essentially risk-free and have maturities comparable to that of the environmental liability. Unless regulatory accounting applies, CMS Energy and Consumers expense legal fees as incurred; fees incurred but not yet billed are accrued based on estimates of work performed.
Debt Issuance Costs, Discounts, Premiums, and Refinancing Costs	Debt Issuance Costs, Discounts, Premiums, and Refinancing Costs: Upon the issuance of long-term debt, CMS Energy and Consumers defer issuance costs, discounts, and premiums and amortize those amounts over the terms of the associated debt. Debt issuance costs are presented as a direct deduction from the carrying amount of long-term debt on the balance sheet. Upon the refinancing of long-term debt, Consumers, as a regulated entity, defers any remaining unamortized issuance costs, discounts, and premiums associated with the refinanced debt and amortizes those amounts over the term of the newly issued debt. For the non‑regulated portions of CMS Energy’s business, any remaining unamortized issuance costs, discounts, and premiums associated with extinguished debt are charged to earnings.
Derivative Instruments	Derivative Instruments: In order to support ongoing operations, CMS Energy and Consumers may enter into contracts for the future purchase and sale of various commodities, such as electricity, natural gas, and coal. These forward contracts are generally long-term in nature and result in physical delivery of the commodity at a contracted price. Most of these contracts are not subject to derivative accounting for one or more of the following reasons: •they do not have a notional amount (that is, a number of units specified in a derivative instrument, such as MWh of electricity or bcf of natural gas) •they qualify for the normal purchases and sales exception •they cannot be net settled due in part to the absence of an active market for the commodity Consumers also uses FTRs to manage price risk related to electricity transmission congestion. An FTR is a financial instrument that entitles its holder to receive compensation or requires its holder to remit payment for congestion-related transmission charges. Consumers accounts for FTRs as derivatives and changes in the fair value of FTRs are deferred as regulatory assets or liabilities. For details regarding CMS Energy’s and Consumers’ derivative instruments recorded at fair value, see Note 5, Fair Value Measurements.
EPS	EPS: CMS Energy calculates basic and diluted EPS using the weighted-average number of shares of common stock and dilutive potential common stock outstanding during the period. Potential common stock, for purposes of determining diluted EPS, includes the effects of nonvested stock awards, forward equity sales, and convertible securities. CMS Energy computes the effect on potential common stock using the treasury stock method. Potentially dilutive common shares issuable upon conversion of the convertible senior notes are determined using the if-converted method for calculating diluted EPS. Diluted EPS excludes the impact of antidilutive securities, which are those securities resulting in an increase in EPS or a decrease in loss per share. For EPS computations, see Note 13, Earnings Per Share—CMS Energy. Nonvested Stock Awards CMS Energy’s nonvested stock awards are composed of participating and non‑participating securities. The participating securities accrue cash dividends when common stockholders receive dividends. Since the recipient is not required to return the dividends to CMS Energy if the recipient forfeits the award, the nonvested stock awards are considered participating securities. As such, the participating nonvested stock awards were included in the computation of basic EPS. The non‑participating securities accrue stock dividends that vest concurrently with the stock award. If the recipient forfeits the award, the stock dividends accrued on the non‑participating securities are also forfeited. Accordingly, the non‑participating awards and stock dividends were included in the computation of diluted EPS, but not in the computation of basic EPS. Forward Equity Sale Contracts CMS Energy has entered into forward equity sale contracts. These forward equity sale contracts are non‑participating securities. While the forward sale price in the forward equity sale contract is decreased on certain dates by certain predetermined amounts to reflect expected dividend payments, these price adjustments were set upon inception of the agreement and the forward contract does not give the owner the right to participate in undistributed earnings. Accordingly, the forward equity sale contracts were included in the computation of diluted EPS, but not in the computation of basic EPS. For further details on the forward equity sale contracts, see Note 4, Financings and Capitalization. Convertible Securities In May 2023, CMS Energy issued an aggregate principal amount of $800 million convertible senior notes. Potentially dilutive common shares issuable upon conversion of the convertible senior notes are determined using the if-converted method for calculating diluted EPS. Upon conversion, the convertible senior notes are required to be paid in cash with only amounts exceeding the principal permitted to be settled in shares. The convertible senior notes were anti-dilutive for the year ended December 31, 2023. For further details on CMS Energy’s convertible senior notes, see Note 4, Financings and Capitalization.
Impairment of Long-Lived Assets	Impairment of Long-lived Assets and Equity Method Investments: CMS Energy and Consumers perform tests of impairment if certain triggering events occur that indicate the carrying amount of an asset may not be recoverable or that there has been a decline in value that may be other than temporary. CMS Energy and Consumers evaluate long-lived assets held in use for impairment by calculating the undiscounted future cash flows expected to result from the use of the asset and its eventual disposition. If the undiscounted future cash flows are less than the carrying amount, CMS Energy and Consumers recognize an impairment loss equal to the amount by which the carrying amount exceeds the fair value. CMS Energy and Consumers estimate the fair value of the asset using quoted market prices, market prices of similar assets, or discounted future cash flow analyses.
Impairment of Equity Method Investments	CMS Energy also assesses equity method investments for impairment whenever there has been a decline in value that is other than temporary. This assessment requires CMS Energy to determine the fair value of the equity method investment. CMS Energy determines fair value using valuation methodologies, including discounted cash flows, and assesses the ability of the investee to sustain an earnings capacity that justifies the carrying amount of the investment. CMS Energy records an impairment if the fair value is less than the carrying amount and the decline in value is considered to be other than temporary.
Investment Tax Credits	Investment Tax Credits: CMS Energy and its subsidiaries use the flow-through method of accounting for investment tax credits. Under the flow-through method, the credit is recognized as a reduction to income tax expense when the related plant, property, and equipment is placed into service. For its regulated utility assets, Consumers amortizes its investment tax credits over the life of the related property in accordance with regulatory treatment.
Inventory - Gas and Coal	Inventory: CMS Energy and Consumers use the weighted-average cost method for valuing working gas, recoverable base gas in underground storage facilities, and materials and supplies inventory. CMS Energy and Consumers also use this method for valuing coal inventory, and they classify these amounts as generating plant fuel stock on their consolidated balance sheets.
Inventory - RECs and Emission Allowances	CMS Energy and Consumers account for RECs and emission allowances as inventory and use the weighted-average cost method to remove amounts from inventory. RECs and emission allowances are used to satisfy compliance obligations related to the generation of power. CMS Energy and Consumers classify these amounts within other assets on their consolidated balance sheets.
Inventory - Impairment	CMS Energy and Consumers evaluate inventory for impairment as required to ensure that its carrying value does not exceed the lower of cost or net realizable value.
MISO Transactions	MISO Transactions: MISO requires the submission of hourly day-ahead and real-time bids and offers for energy at locations across the MISO region. CMS Energy and Consumers account for MISO transactions on a net hourly basis in each of the real-time and day-ahead markets, netted across all MISO energy market locations. CMS Energy and Consumers record net hourly purchases in purchased and interchange power and net hourly sales in operating revenue on their consolidated statements of income. They record net billing adjustments upon receipt of settlement statements, record accruals for future net purchases and sales adjustments based on historical experience, and reconcile accruals to actual expenses and sales upon receipt of settlement statements.
Property Taxes	Property Taxes: Property taxes are based on the taxable value of CMS Energy’s and Consumers’ real and personal property assessed by local taxing authorities. CMS Energy and Consumers record property tax expense over the fiscal year of the taxing authority for which the taxes are levied. The deferred property tax balance represents the amount of CMS Energy’s and Consumers’ accrued property tax that will be recognized over future governmental fiscal periods. Other: For additional accounting policies, see:
Capitalization	Capitalization: CMS Energy and Consumers record plant, property, and equipment at original cost when placed into service. The cost includes labor, material, applicable taxes, overhead such as pension and other benefits, and AFUDC, if applicable. Consumers’ plant, property, and equipment is generally recoverable through its general ratemaking process. Software: CMS Energy and Consumers capitalize the costs to purchase and develop internal-use computer software. These costs are expensed evenly over the estimated useful life of the internal-use computer software. If computer software is integral to computer hardware, then its cost is capitalized and depreciated with the hardware.
Plant Retirement and Abandonment	With the exception of utility property for which the remaining book value has been securitized, mothballed utility property stays in rate base and continues to be depreciated at the same rate as before the mothball period. When utility property is retired or otherwise disposed of in the ordinary course of business, Consumers records the original cost to accumulated depreciation, along with associated cost of removal, net of salvage. CMS Energy and Consumers recognize gains or losses on the retirement or disposal of non‑regulated assets in income. Consumers records cost of removal collected from customers, but not spent, as a regulatory liability.
AFUDC	AFUDC: Consumers capitalizes AFUDC on regulated major construction projects. AFUDC represents the estimated cost of debt and authorized return-on-equity funds used to finance construction additions. Consumers records the offsetting credit as a reduction of interest for the amount representing the borrowed funds component and as other income for the equity funds component on the consolidated statements of income. When construction is completed and the property is placed in service, Consumers depreciates and recovers the capitalized AFUDC from customers over the life of the related asset.
Planned Major Maintenance Activities	CMS Energy and Consumers record property repairs and minor property replacement as maintenance expense. CMS Energy and Consumers record planned major maintenance activities as operating expense unless the cost represents the acquisition of additional long-lived assets or the replacement of an existing long-lived asset.
Lessee	Lessee CMS Energy and Consumers lease various assets from third parties, including coal-carrying railcars, real estate, service vehicles, and gas pipeline capacity. In addition, CMS Energy and Consumers account for several of their PPAs as leases. CMS Energy and Consumers do not record right-of-use assets or lease liabilities on their consolidated balance sheets for rentals with lease terms of 12 months or less, most of which are for the lease of real estate and service vehicles. Lease expense for these rentals is recognized on a straight-line basis over the lease term. CMS Energy and Consumers include future payments for all renewal options, fair market value extensions, and buyout provisions reasonably certain of exercise in their measurement of lease right-of-use assets and lease liabilities. In addition, certain leases for service vehicles contain end-of-lease adjustment clauses based on proceeds received from the sale or disposition of the vehicles. CMS Energy and Consumers also include executory costs in the measurement of their right-of-use assets and lease liabilities, except for maintenance costs related to their coal-carrying railcar leases. Most of Consumers’ PPAs contain provisions at the end of the initial contract terms to renew the agreements annually under mutually agreed‑upon terms at the time of renewal. Energy and capacity payments that vary depending on quantities delivered are recognized as variable lease costs when incurred. Consumers accounts for a PPA with one of CMS Energy’s equity method subsidiaries as a finance lease.
Asset Retirement Obligations	CMS Energy and Consumers record the fair value of the cost to remove assets at the end of their useful lives, if there is a legal obligation to remove them. If a reasonable estimate of fair value cannot be made in the period in which the ARO is incurred, such as for assets with indeterminate lives, the liability is recognized when a reasonable estimate of fair value can be made. CMS Energy and Consumers have not recorded liabilities associated with the closure of certain gas wells that have an indeterminate life. CMS Energy and Consumers have not recorded liabilities for assets that have immaterial cumulative disposal costs, such as substation batteries. CMS Energy and Consumers calculate the fair value of ARO liabilities using an expected present-value technique that reflects assumptions about costs and inflation, and uses a credit-adjusted risk-free rate to discount the expected cash flows. CMS Energy’s ARO liabilities are primarily at Consumers.
Retirement Benefits - Pension	The mortality assumption for benefit obligations was based on the Pri-2012 Mortality Table, with improvement scale MP-2021. The mortality assumption for net periodic benefit cost was based on the Pri-2012 Mortality Table, with improvement scale MP-2021 for 2023 and 2022 and improvement scale MP-2020 for 2021. 2The discount rate reflects the rate at which benefits could be effectively settled and is equal to the equivalent single rate resulting from a yield-curve analysis. This analysis incorporated the projected benefit payments specific to CMS Energy’s and Consumers’ DB Pension Plans and OPEB Plan and the yields on high-quality corporate bonds rated Aa or better. 3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023. 4CMS Energy and Consumers have elected to use a full-yield-curve approach in the estimation of service cost and interest cost; this approach applies individual spot rates along the yield curve to future projected benefit payments based on the time of payment. 5CMS Energy and Consumers determined the long-term rate of return using historical market returns, the present and expected future economic environment, the capital market principles of risk and return, and the expert opinions of individuals and firms with financial market knowledge. CMS Energy and Consumers considered the asset allocation of the portfolio in forecasting the future expected total return of the portfolio. The goal was to determine a long-term rate of return that could be incorporated into the planning of future cash flow requirements in conjunction with the change in the liability. Annually, CMS Energy and Consumers review for reasonableness and appropriateness the forecasted returns for various classes of assets used to construct an expected return model. CMS Energy’s and Consumers’ expected long-term rate of return on the assets of the DB Pension Plans was 7.20 percent in 2023. The actual return (loss) on the assets of the DB Pension Plans was 12.6 percent in 2023, (15.9) percent in 2022, and 12.0 percent in 2021. CMS Energy and Consumers amortize net gains and losses in excess of ten percent of the greater of the PBO or the MRV over the average remaining service period for DB Pension Plan A and the OPEB Plan and over the average remaining life expectancy of participants for DB Pension Plan B. For DB Pension Plan A, the estimated period of amortization of gains and losses was eight years for the years ended December 31, 2023, 2022, and 2021. For DB Pension Plan B, the estimated period of amortization of gains and losses was 17 years for the year ended December 31, 2023, and 18 years for the years ended December 31, 2022 and 2021. For the OPEB Plan, the estimated amortization period was nine years for the years ended December 31, 2023, 2022, and 2021. Prior service cost (credit) amortization is established in the year in which the prior service cost (credit) first occurred, and is based on the same amortization period for all future years until the prior service cost (credit) is fully amortized. CMS Energy and Consumers had new prior service costs for OPEB in 2020. The estimated period of amortization of these new prior service costs is eight years. CMS Energy and Consumers determine the MRV for the assets of the DB Pension Plans as the fair value of plan assets on the measurement date, adjusted by the gains or losses that will not be admitted into the MRV until future years. CMS Energy and Consumers reflect each year’s gain or loss in the MRV in equal amounts over a five‑year period beginning on the date the original amount was determined. CMS Energy and Consumers determine the MRV for OPEB Plan assets as the fair value of assets on the measurement date.
Retirement Benefits - Nonpension	The mortality assumption for benefit obligations was based on the Pri-2012 Mortality Table, with improvement scale MP-2021. The mortality assumption for net periodic benefit cost was based on the Pri-2012 Mortality Table, with improvement scale MP-2021 for 2023 and 2022 and improvement scale MP-2020 for 2021. 2The discount rate reflects the rate at which benefits could be effectively settled and is equal to the equivalent single rate resulting from a yield-curve analysis. This analysis incorporated the projected benefit payments specific to CMS Energy’s and Consumers’ DB Pension Plans and OPEB Plan and the yields on high-quality corporate bonds rated Aa or better. 3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023. 4CMS Energy and Consumers have elected to use a full-yield-curve approach in the estimation of service cost and interest cost; this approach applies individual spot rates along the yield curve to future projected benefit payments based on the time of payment. 5CMS Energy and Consumers determined the long-term rate of return using historical market returns, the present and expected future economic environment, the capital market principles of risk and return, and the expert opinions of individuals and firms with financial market knowledge. CMS Energy and Consumers considered the asset allocation of the portfolio in forecasting the future expected total return of the portfolio. The goal was to determine a long-term rate of return that could be incorporated into the planning of future cash flow requirements in conjunction with the change in the liability. Annually, CMS Energy and Consumers review for reasonableness and appropriateness the forecasted returns for various classes of assets used to construct an expected return model. CMS Energy’s and Consumers’ expected long-term rate of return on the assets of the DB Pension Plans was 7.20 percent in 2023. The actual return (loss) on the assets of the DB Pension Plans was 12.6 percent in 2023, (15.9) percent in 2022, and 12.0 percent in 2021. CMS Energy and Consumers amortize net gains and losses in excess of ten percent of the greater of the PBO or the MRV over the average remaining service period for DB Pension Plan A and the OPEB Plan and over the average remaining life expectancy of participants for DB Pension Plan B. For DB Pension Plan A, the estimated period of amortization of gains and losses was eight years for the years ended December 31, 2023, 2022, and 2021. For DB Pension Plan B, the estimated period of amortization of gains and losses was 17 years for the year ended December 31, 2023, and 18 years for the years ended December 31, 2022 and 2021. For the OPEB Plan, the estimated amortization period was nine years for the years ended December 31, 2023, 2022, and 2021. Prior service cost (credit) amortization is established in the year in which the prior service cost (credit) first occurred, and is based on the same amortization period for all future years until the prior service cost (credit) is fully amortized. CMS Energy and Consumers had new prior service costs for OPEB in 2020. The estimated period of amortization of these new prior service costs is eight years. CMS Energy and Consumers determine the MRV for the assets of the DB Pension Plans as the fair value of plan assets on the measurement date, adjusted by the gains or losses that will not be admitted into the MRV until future years. CMS Energy and Consumers reflect each year’s gain or loss in the MRV in equal amounts over a five‑year period beginning on the date the original amount was determined. CMS Energy and Consumers determine the MRV for OPEB Plan assets as the fair value of assets on the measurement date.
Income taxes	CMS Energy and its subsidiaries file a consolidated U.S. federal income tax return as well as a Michigan Corporate Income Tax return for the unitary business group and various other state unitary group combined income tax returns. Income taxes are allocated based on each company’s separate taxable income in accordance with the CMS Energy tax sharing agreement.
Accounts Receivable	Accounts Receivable and Unbilled Revenues: Accounts receivable comprise trade receivables and unbilled receivables. CMS Energy and Consumers record their accounts receivable at cost less an allowance for uncollectible accounts. The allowance is increased for uncollectible accounts expense and decreased for account write-offs net of recoveries. CMS Energy and Consumers establish the allowance based on historical losses, management’s assessment of existing economic conditions, customer payment trends, and reasonable and supported forecast information. CMS Energy and Consumers assess late payment fees on trade receivables based on contractual past-due terms established with customers. Accounts are written off when deemed uncollectible, which is generally when they become six months past due.
Consolidation, Variable Interest Entity	Newport Solar Holdings, NWO Holdco, Aviator Wind Equity Holdings, and Aviator Wind are VIEs. In accordance with the associated limited liability company agreements, the tax equity investors are guaranteed preferred returns from these entities. However, NorthStar Clean Energy manages and controls the entities’ operating activities. As a result, NorthStar Clean Energy is the primary beneficiary, as it has the power to direct the activities that most significantly impact the economic performance of the companies, as well as the obligation to absorb losses or the right to receive benefits from the companies.CMS Energy has variable interests in T.E.S. Filer City, Grayling, Genesee, and Craven. While CMS Energy owns 50 percent of each partnership, it is not the primary beneficiary of any of these partnerships because decision making is shared among unrelated parties, and no one party has the ability to direct the activities that most significantly impact the entities’ economic performance, such as operations and maintenance, plant dispatch, and fuel strategy. The partners must agree on all major decisions for each of the partnerships.
Consumers Energy Company
Significant Accounting Policies [Line Items]
Principles of Consolidation	Principles of Consolidation: CMS Energy and Consumers prepare their consolidated financial statements in conformity with GAAP. CMS Energy’s consolidated financial statements comprise CMS Energy, Consumers, NorthStar Clean Energy, and all other entities in which CMS Energy has a controlling financial interest or is the primary beneficiary. Consumers’ consolidated financial statements comprise Consumers and all other entities in which it has a controlling financial interest. CMS Energy uses the equity method of accounting for investments in companies and partnerships that are not consolidated, where they have significant influence over operations and financial policies but are not the primary beneficiary. CMS Energy and Consumers eliminate intercompany transactions and balances.
Use of Estimates	Use of Estimates: CMS Energy and Consumers are required to make estimates using assumptions that may affect reported amounts and disclosures. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents and Restricted Cash and Cash Equivalents: Cash and cash equivalents include short-term, highly liquid investments with original maturities of three months or less. Restricted cash and cash equivalents are held primarily for the repayment of securitization bonds and funds held in escrow. Cash and cash equivalents may also be restricted to pay other contractual obligations such as leasing of coal railcars. These amounts are classified as current assets since they relate to payments that could or will occur within one year.
Restricted Cash and Cash Equivalents	Cash and Cash Equivalents and Restricted Cash and Cash Equivalents: Cash and cash equivalents include short-term, highly liquid investments with original maturities of three months or less. Restricted cash and cash equivalents are held primarily for the repayment of securitization bonds and funds held in escrow. Cash and cash equivalents may also be restricted to pay other contractual obligations such as leasing of coal railcars. These amounts are classified as current assets since they relate to payments that could or will occur within one year.
Contingencies	Contingencies: CMS Energy and Consumers record estimated loss contingencies on their consolidated financial statements when it is probable that a loss has been incurred and when the amount of loss can be reasonably estimated. For environmental remediation projects in which the timing of estimated expenditures is considered reliably determinable, CMS Energy and Consumers record the liability at its net present value, using a discount rate equal to the interest rate on monetary assets that are essentially risk-free and have maturities comparable to that of the environmental liability. Unless regulatory accounting applies, CMS Energy and Consumers expense legal fees as incurred; fees incurred but not yet billed are accrued based on estimates of work performed.
Debt Issuance Costs, Discounts, Premiums, and Refinancing Costs	Debt Issuance Costs, Discounts, Premiums, and Refinancing Costs: Upon the issuance of long-term debt, CMS Energy and Consumers defer issuance costs, discounts, and premiums and amortize those amounts over the terms of the associated debt. Debt issuance costs are presented as a direct deduction from the carrying amount of long-term debt on the balance sheet. Upon the refinancing of long-term debt, Consumers, as a regulated entity, defers any remaining unamortized issuance costs, discounts, and premiums associated with the refinanced debt and amortizes those amounts over the term of the newly issued debt. For the non‑regulated portions of CMS Energy’s business, any remaining unamortized issuance costs, discounts, and premiums associated with extinguished debt are charged to earnings.
Derivative Instruments	Derivative Instruments: In order to support ongoing operations, CMS Energy and Consumers may enter into contracts for the future purchase and sale of various commodities, such as electricity, natural gas, and coal. These forward contracts are generally long-term in nature and result in physical delivery of the commodity at a contracted price. Most of these contracts are not subject to derivative accounting for one or more of the following reasons: •they do not have a notional amount (that is, a number of units specified in a derivative instrument, such as MWh of electricity or bcf of natural gas) •they qualify for the normal purchases and sales exception •they cannot be net settled due in part to the absence of an active market for the commodity Consumers also uses FTRs to manage price risk related to electricity transmission congestion. An FTR is a financial instrument that entitles its holder to receive compensation or requires its holder to remit payment for congestion-related transmission charges. Consumers accounts for FTRs as derivatives and changes in the fair value of FTRs are deferred as regulatory assets or liabilities. For details regarding CMS Energy’s and Consumers’ derivative instruments recorded at fair value, see Note 5, Fair Value Measurements.
Impairment of Long-Lived Assets	Impairment of Long-lived Assets and Equity Method Investments: CMS Energy and Consumers perform tests of impairment if certain triggering events occur that indicate the carrying amount of an asset may not be recoverable or that there has been a decline in value that may be other than temporary. CMS Energy and Consumers evaluate long-lived assets held in use for impairment by calculating the undiscounted future cash flows expected to result from the use of the asset and its eventual disposition. If the undiscounted future cash flows are less than the carrying amount, CMS Energy and Consumers recognize an impairment loss equal to the amount by which the carrying amount exceeds the fair value. CMS Energy and Consumers estimate the fair value of the asset using quoted market prices, market prices of similar assets, or discounted future cash flow analyses.
Investment Tax Credits	Investment Tax Credits: CMS Energy and its subsidiaries use the flow-through method of accounting for investment tax credits. Under the flow-through method, the credit is recognized as a reduction to income tax expense when the related plant, property, and equipment is placed into service. For its regulated utility assets, Consumers amortizes its investment tax credits over the life of the related property in accordance with regulatory treatment.
Inventory - Gas and Coal	Inventory: CMS Energy and Consumers use the weighted-average cost method for valuing working gas, recoverable base gas in underground storage facilities, and materials and supplies inventory. CMS Energy and Consumers also use this method for valuing coal inventory, and they classify these amounts as generating plant fuel stock on their consolidated balance sheets.
Inventory - RECs and Emission Allowances	CMS Energy and Consumers account for RECs and emission allowances as inventory and use the weighted-average cost method to remove amounts from inventory. RECs and emission allowances are used to satisfy compliance obligations related to the generation of power. CMS Energy and Consumers classify these amounts within other assets on their consolidated balance sheets.
Inventory - Impairment	CMS Energy and Consumers evaluate inventory for impairment as required to ensure that its carrying value does not exceed the lower of cost or net realizable value.
MISO Transactions	MISO Transactions: MISO requires the submission of hourly day-ahead and real-time bids and offers for energy at locations across the MISO region. CMS Energy and Consumers account for MISO transactions on a net hourly basis in each of the real-time and day-ahead markets, netted across all MISO energy market locations. CMS Energy and Consumers record net hourly purchases in purchased and interchange power and net hourly sales in operating revenue on their consolidated statements of income. They record net billing adjustments upon receipt of settlement statements, record accruals for future net purchases and sales adjustments based on historical experience, and reconcile accruals to actual expenses and sales upon receipt of settlement statements.
Property Taxes	Property Taxes: Property taxes are based on the taxable value of CMS Energy’s and Consumers’ real and personal property assessed by local taxing authorities. CMS Energy and Consumers record property tax expense over the fiscal year of the taxing authority for which the taxes are levied. The deferred property tax balance represents the amount of CMS Energy’s and Consumers’ accrued property tax that will be recognized over future governmental fiscal periods. Other: For additional accounting policies, see:
Government Assistance	Renewable Energy Grant: In 2013, Consumers received a $69 million renewable energy grant for Lake Winds® Energy Park, which began operations in 2012. This grant reduces Consumers’ cost of complying with Michigan’s renewable portfolio standard and, accordingly, reduces the overall renewable energy surcharge to be collected from customers. The regulatory liability recorded for the grant will be amortized over the life of Lake Winds® Energy Park. Consumers presents the amortization as a reduction to maintenance and other operating expenses on its consolidated statements of income.
Capitalization	Capitalization: CMS Energy and Consumers record plant, property, and equipment at original cost when placed into service. The cost includes labor, material, applicable taxes, overhead such as pension and other benefits, and AFUDC, if applicable. Consumers’ plant, property, and equipment is generally recoverable through its general ratemaking process. Software: CMS Energy and Consumers capitalize the costs to purchase and develop internal-use computer software. These costs are expensed evenly over the estimated useful life of the internal-use computer software. If computer software is integral to computer hardware, then its cost is capitalized and depreciated with the hardware.
Plant Retirement and Abandonment	With the exception of utility property for which the remaining book value has been securitized, mothballed utility property stays in rate base and continues to be depreciated at the same rate as before the mothball period. When utility property is retired or otherwise disposed of in the ordinary course of business, Consumers records the original cost to accumulated depreciation, along with associated cost of removal, net of salvage. CMS Energy and Consumers recognize gains or losses on the retirement or disposal of non‑regulated assets in income. Consumers records cost of removal collected from customers, but not spent, as a regulatory liability.
AFUDC	AFUDC: Consumers capitalizes AFUDC on regulated major construction projects. AFUDC represents the estimated cost of debt and authorized return-on-equity funds used to finance construction additions. Consumers records the offsetting credit as a reduction of interest for the amount representing the borrowed funds component and as other income for the equity funds component on the consolidated statements of income. When construction is completed and the property is placed in service, Consumers depreciates and recovers the capitalized AFUDC from customers over the life of the related asset.
Regulatory Depreciation and Amortization	Consumers depreciates utility property on an asset-group basis, in which it applies a single MPSC-approved depreciation rate to the gross investment in a particular class of property within the electric and gas segments. Consumers performs depreciation studies periodically to determine appropriate group lives.
Planned Major Maintenance Activities	CMS Energy and Consumers record property repairs and minor property replacement as maintenance expense. CMS Energy and Consumers record planned major maintenance activities as operating expense unless the cost represents the acquisition of additional long-lived assets or the replacement of an existing long-lived asset.
Lessee	Lessee CMS Energy and Consumers lease various assets from third parties, including coal-carrying railcars, real estate, service vehicles, and gas pipeline capacity. In addition, CMS Energy and Consumers account for several of their PPAs as leases. CMS Energy and Consumers do not record right-of-use assets or lease liabilities on their consolidated balance sheets for rentals with lease terms of 12 months or less, most of which are for the lease of real estate and service vehicles. Lease expense for these rentals is recognized on a straight-line basis over the lease term. CMS Energy and Consumers include future payments for all renewal options, fair market value extensions, and buyout provisions reasonably certain of exercise in their measurement of lease right-of-use assets and lease liabilities. In addition, certain leases for service vehicles contain end-of-lease adjustment clauses based on proceeds received from the sale or disposition of the vehicles. CMS Energy and Consumers also include executory costs in the measurement of their right-of-use assets and lease liabilities, except for maintenance costs related to their coal-carrying railcar leases. Most of Consumers’ PPAs contain provisions at the end of the initial contract terms to renew the agreements annually under mutually agreed‑upon terms at the time of renewal. Energy and capacity payments that vary depending on quantities delivered are recognized as variable lease costs when incurred. Consumers accounts for a PPA with one of CMS Energy’s equity method subsidiaries as a finance lease.
Asset Retirement Obligations	CMS Energy and Consumers record the fair value of the cost to remove assets at the end of their useful lives, if there is a legal obligation to remove them. If a reasonable estimate of fair value cannot be made in the period in which the ARO is incurred, such as for assets with indeterminate lives, the liability is recognized when a reasonable estimate of fair value can be made. CMS Energy and Consumers have not recorded liabilities associated with the closure of certain gas wells that have an indeterminate life. CMS Energy and Consumers have not recorded liabilities for assets that have immaterial cumulative disposal costs, such as substation batteries. CMS Energy and Consumers calculate the fair value of ARO liabilities using an expected present-value technique that reflects assumptions about costs and inflation, and uses a credit-adjusted risk-free rate to discount the expected cash flows. CMS Energy’s ARO liabilities are primarily at Consumers.
Retirement Benefits - Pension	The mortality assumption for benefit obligations was based on the Pri-2012 Mortality Table, with improvement scale MP-2021. The mortality assumption for net periodic benefit cost was based on the Pri-2012 Mortality Table, with improvement scale MP-2021 for 2023 and 2022 and improvement scale MP-2020 for 2021. 2The discount rate reflects the rate at which benefits could be effectively settled and is equal to the equivalent single rate resulting from a yield-curve analysis. This analysis incorporated the projected benefit payments specific to CMS Energy’s and Consumers’ DB Pension Plans and OPEB Plan and the yields on high-quality corporate bonds rated Aa or better. 3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023. 4CMS Energy and Consumers have elected to use a full-yield-curve approach in the estimation of service cost and interest cost; this approach applies individual spot rates along the yield curve to future projected benefit payments based on the time of payment. 5CMS Energy and Consumers determined the long-term rate of return using historical market returns, the present and expected future economic environment, the capital market principles of risk and return, and the expert opinions of individuals and firms with financial market knowledge. CMS Energy and Consumers considered the asset allocation of the portfolio in forecasting the future expected total return of the portfolio. The goal was to determine a long-term rate of return that could be incorporated into the planning of future cash flow requirements in conjunction with the change in the liability. Annually, CMS Energy and Consumers review for reasonableness and appropriateness the forecasted returns for various classes of assets used to construct an expected return model. CMS Energy’s and Consumers’ expected long-term rate of return on the assets of the DB Pension Plans was 7.20 percent in 2023. The actual return (loss) on the assets of the DB Pension Plans was 12.6 percent in 2023, (15.9) percent in 2022, and 12.0 percent in 2021. CMS Energy and Consumers amortize net gains and losses in excess of ten percent of the greater of the PBO or the MRV over the average remaining service period for DB Pension Plan A and the OPEB Plan and over the average remaining life expectancy of participants for DB Pension Plan B. For DB Pension Plan A, the estimated period of amortization of gains and losses was eight years for the years ended December 31, 2023, 2022, and 2021. For DB Pension Plan B, the estimated period of amortization of gains and losses was 17 years for the year ended December 31, 2023, and 18 years for the years ended December 31, 2022 and 2021. For the OPEB Plan, the estimated amortization period was nine years for the years ended December 31, 2023, 2022, and 2021. Prior service cost (credit) amortization is established in the year in which the prior service cost (credit) first occurred, and is based on the same amortization period for all future years until the prior service cost (credit) is fully amortized. CMS Energy and Consumers had new prior service costs for OPEB in 2020. The estimated period of amortization of these new prior service costs is eight years. CMS Energy and Consumers determine the MRV for the assets of the DB Pension Plans as the fair value of plan assets on the measurement date, adjusted by the gains or losses that will not be admitted into the MRV until future years. CMS Energy and Consumers reflect each year’s gain or loss in the MRV in equal amounts over a five‑year period beginning on the date the original amount was determined. CMS Energy and Consumers determine the MRV for OPEB Plan assets as the fair value of assets on the measurement date.
Retirement Benefits - Nonpension	The mortality assumption for benefit obligations was based on the Pri-2012 Mortality Table, with improvement scale MP-2021. The mortality assumption for net periodic benefit cost was based on the Pri-2012 Mortality Table, with improvement scale MP-2021 for 2023 and 2022 and improvement scale MP-2020 for 2021. 2The discount rate reflects the rate at which benefits could be effectively settled and is equal to the equivalent single rate resulting from a yield-curve analysis. This analysis incorporated the projected benefit payments specific to CMS Energy’s and Consumers’ DB Pension Plans and OPEB Plan and the yields on high-quality corporate bonds rated Aa or better. 3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023. 4CMS Energy and Consumers have elected to use a full-yield-curve approach in the estimation of service cost and interest cost; this approach applies individual spot rates along the yield curve to future projected benefit payments based on the time of payment. 5CMS Energy and Consumers determined the long-term rate of return using historical market returns, the present and expected future economic environment, the capital market principles of risk and return, and the expert opinions of individuals and firms with financial market knowledge. CMS Energy and Consumers considered the asset allocation of the portfolio in forecasting the future expected total return of the portfolio. The goal was to determine a long-term rate of return that could be incorporated into the planning of future cash flow requirements in conjunction with the change in the liability. Annually, CMS Energy and Consumers review for reasonableness and appropriateness the forecasted returns for various classes of assets used to construct an expected return model. CMS Energy’s and Consumers’ expected long-term rate of return on the assets of the DB Pension Plans was 7.20 percent in 2023. The actual return (loss) on the assets of the DB Pension Plans was 12.6 percent in 2023, (15.9) percent in 2022, and 12.0 percent in 2021. CMS Energy and Consumers amortize net gains and losses in excess of ten percent of the greater of the PBO or the MRV over the average remaining service period for DB Pension Plan A and the OPEB Plan and over the average remaining life expectancy of participants for DB Pension Plan B. For DB Pension Plan A, the estimated period of amortization of gains and losses was eight years for the years ended December 31, 2023, 2022, and 2021. For DB Pension Plan B, the estimated period of amortization of gains and losses was 17 years for the year ended December 31, 2023, and 18 years for the years ended December 31, 2022 and 2021. For the OPEB Plan, the estimated amortization period was nine years for the years ended December 31, 2023, 2022, and 2021. Prior service cost (credit) amortization is established in the year in which the prior service cost (credit) first occurred, and is based on the same amortization period for all future years until the prior service cost (credit) is fully amortized. CMS Energy and Consumers had new prior service costs for OPEB in 2020. The estimated period of amortization of these new prior service costs is eight years. CMS Energy and Consumers determine the MRV for the assets of the DB Pension Plans as the fair value of plan assets on the measurement date, adjusted by the gains or losses that will not be admitted into the MRV until future years. CMS Energy and Consumers reflect each year’s gain or loss in the MRV in equal amounts over a five‑year period beginning on the date the original amount was determined. CMS Energy and Consumers determine the MRV for OPEB Plan assets as the fair value of assets on the measurement date.
Income taxes	CMS Energy and its subsidiaries file a consolidated U.S. federal income tax return as well as a Michigan Corporate Income Tax return for the unitary business group and various other state unitary group combined income tax returns. Income taxes are allocated based on each company’s separate taxable income in accordance with the CMS Energy tax sharing agreement.
Consumers Utility Revenue	Consumers Utility Revenue: Consumers recognizes revenue primarily from the sale of electric and gas utility services at tariff-based rates regulated by the MPSC. Consumers’ customer base consists of a mix of residential, commercial, and diversified industrial customers. Consumers’ tariff-based sales performance obligations are described below. •Consumers has performance obligations for the service of standing ready to deliver electricity or natural gas to customers, and it satisfies these performance obligations over time. Consumers recognizes revenue at a fixed rate as it provides these services. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of Consumers’ service to stand ready to deliver. •Consumers has performance obligations for the service of delivering the commodity of electricity or natural gas to customers, and it satisfies these performance obligations upon delivery. Consumers recognizes revenue at a price per unit of electricity or natural gas delivered, based on the tariffs established by the MPSC. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of a bundled product comprising the commodity, electricity or natural gas, and the service of delivering such commodity. In some instances, Consumers has specific fixed-term contracts with large commercial and industrial customers to provide electricity or gas at certain tariff rates or to provide gas transportation services at contracted rates. The amount of electricity and gas to be delivered under these contracts and the associated future revenue to be received are generally dependent on the customers’ needs. Accordingly, Consumers recognizes revenues at the tariff or contracted rate as electricity or gas is delivered to the customer. Consumers also has other miscellaneous contracts with customers related to pole and other property rentals, appliance service plans, and utility contract work. Generally, these contracts are short term or evergreen in nature.
Accounts Receivable	Accounts Receivable and Unbilled Revenues: Accounts receivable comprise trade receivables and unbilled receivables. CMS Energy and Consumers record their accounts receivable at cost less an allowance for uncollectible accounts. The allowance is increased for uncollectible accounts expense and decreased for account write-offs net of recoveries. CMS Energy and Consumers establish the allowance based on historical losses, management’s assessment of existing economic conditions, customer payment trends, and reasonable and supported forecast information. CMS Energy and Consumers assess late payment fees on trade receivables based on contractual past-due terms established with customers. Accounts are written off when deemed uncollectible, which is generally when they become six months past due.
Unbilled Revenues	Consumers’ customers are billed monthly in cycles having billing dates that do not generally coincide with the end of a calendar month. This results in customers having received electricity or natural gas that they have not been billed for as of the month-end. Consumers estimates its unbilled revenues by applying an average billed rate to total unbilled deliveries for each customer class.
Alternative-revenue Programs	Alternative‑revenue Programs: Consumers accounts for its energy waste reduction incentive mechanism and financial compensation mechanism as alternative-revenue programs. Consumers recognizes revenue related to the energy waste reduction incentive as soon as energy savings exceed the annual targets established by the MPSC and recognizes revenue related to the financial compensation mechanism as payments are made on MPSC-approved PPAs. For additional information on these mechanisms, see Note 2, Regulatory Matters. Consumers does not reclassify revenue from its alternative-revenue program to revenue from contracts with customers at the time the amounts are collected from customers.

Significant Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2023

Significant Accounting Policies [Line Items]

Principles of Consolidation: CMS Energy and Consumers prepare their consolidated financial statements in conformity with GAAP. CMS Energy’s consolidated financial statements comprise CMS Energy, Consumers, NorthStar Clean Energy, and all other entities in which CMS Energy has a controlling financial interest or is the primary beneficiary. Consumers’ consolidated financial statements comprise Consumers and all other entities in which it has a controlling financial interest. CMS Energy uses the equity method of accounting for investments in companies and partnerships that are not consolidated, where they have significant influence over operations and financial policies but are not the primary beneficiary. CMS Energy and Consumers eliminate intercompany transactions and balances.

Use of Estimates

Use of Estimates: CMS Energy and Consumers are required to make estimates using assumptions that may affect reported amounts and disclosures. Actual results could differ from those estimates.

Cash and Cash Equivalents

Cash and Cash Equivalents and Restricted Cash and Cash Equivalents: Cash and cash equivalents include short-term, highly liquid investments with original maturities of three months or less. Restricted cash and cash equivalents are held primarily for the repayment of securitization bonds and funds held in escrow. Cash and cash equivalents may also be restricted to pay other contractual obligations such as leasing of coal railcars. These amounts are classified as current assets since they relate to payments that could or will occur within one year.

Restricted Cash and Cash Equivalents

Contingencies

Contingencies: CMS Energy and Consumers record estimated loss contingencies on their consolidated financial statements when it is probable that a loss has been incurred and when the amount of loss can be reasonably estimated. For environmental remediation projects in which the timing of estimated expenditures is considered reliably determinable, CMS Energy and Consumers record the liability at its net present value, using a discount rate equal to the interest rate on monetary assets that are essentially risk-free and have maturities comparable to that of the environmental liability. Unless regulatory accounting applies, CMS Energy and Consumers expense legal fees as incurred; fees incurred but not yet billed are accrued based on estimates of work performed.

Debt Issuance Costs, Discounts, Premiums, and Refinancing Costs

Debt Issuance Costs, Discounts, Premiums, and Refinancing Costs: Upon the issuance of long-term debt, CMS Energy and Consumers defer issuance costs, discounts, and premiums and amortize those amounts over the terms of the associated debt. Debt issuance costs are presented as a direct deduction from the carrying amount of long-term debt on the balance sheet. Upon the refinancing of long-term debt, Consumers, as a regulated entity, defers any remaining unamortized issuance costs, discounts, and premiums associated with the refinanced debt and amortizes those amounts over the term of the newly issued debt. For the non‑regulated portions of CMS Energy’s business, any remaining unamortized issuance costs, discounts, and premiums associated with extinguished debt are charged to earnings.

Derivative Instruments

Derivative Instruments: In order to support ongoing operations, CMS Energy and Consumers may enter into contracts for the future purchase and sale of various commodities, such as electricity, natural gas, and coal. These forward contracts are generally long-term in nature and result in physical delivery of the

commodity at a contracted price. Most of these contracts are not subject to derivative accounting for one or more of the following reasons:

•they do not have a notional amount (that is, a number of units specified in a derivative instrument, such as MWh of electricity or bcf of natural gas)

•they qualify for the normal purchases and sales exception

•they cannot be net settled due in part to the absence of an active market for the commodity

Consumers also uses FTRs to manage price risk related to electricity transmission congestion. An FTR is a financial instrument that entitles its holder to receive compensation or requires its holder to remit payment for congestion-related transmission charges. Consumers accounts for FTRs as derivatives and changes in the fair value of FTRs are deferred as regulatory assets or liabilities. For details regarding CMS Energy’s and Consumers’ derivative instruments recorded at fair value, see Note 5, Fair Value Measurements.

EPS

EPS: CMS Energy calculates basic and diluted EPS using the weighted-average number of shares of common stock and dilutive potential common stock outstanding during the period. Potential common stock, for purposes of determining diluted EPS, includes the effects of nonvested stock awards, forward equity sales, and convertible securities. CMS Energy computes the effect on potential common stock using the treasury stock method. Potentially dilutive common shares issuable upon conversion of the convertible senior notes are determined using the if-converted method for calculating diluted EPS. Diluted EPS excludes the impact of antidilutive securities, which are those securities resulting in an increase in EPS or a decrease in loss per share. For EPS computations, see Note 13, Earnings Per Share—CMS Energy.

Nonvested Stock Awards

CMS Energy’s nonvested stock awards are composed of participating and non‑participating securities. The participating securities accrue cash dividends when common stockholders receive dividends. Since the recipient is not required to return the dividends to CMS Energy if the recipient forfeits the award, the nonvested stock awards are considered participating securities. As such, the participating nonvested stock awards were included in the computation of basic EPS. The non‑participating securities accrue stock dividends that vest concurrently with the stock award. If the recipient forfeits the award, the stock dividends accrued on the non‑participating securities are also forfeited. Accordingly, the non‑participating awards and stock dividends were included in the computation of diluted EPS, but not in the computation of basic EPS.

Forward Equity Sale Contracts

CMS Energy has entered into forward equity sale contracts. These forward equity sale contracts are non‑participating securities. While the forward sale price in the forward equity sale contract is decreased on certain dates by certain predetermined amounts to reflect expected dividend payments, these price adjustments were set upon inception of the agreement and the forward contract does not give the owner the right to participate in undistributed earnings. Accordingly, the forward equity sale contracts were

included in the computation of diluted EPS, but not in the computation of basic EPS. For further details on the forward equity sale contracts, see Note 4, Financings and Capitalization.

Convertible Securities

In May 2023, CMS Energy issued an aggregate principal amount of $800 million convertible senior notes. Potentially dilutive common shares issuable upon conversion of the convertible senior notes are determined using the if-converted method for calculating diluted EPS. Upon conversion, the convertible senior notes are required to be paid in cash with only amounts exceeding the principal permitted to be settled in shares. The convertible senior notes were anti-dilutive for the year ended December 31, 2023. For further details on CMS Energy’s convertible senior notes, see Note 4, Financings and Capitalization.

Impairment of Long-Lived Assets

Impairment of Long-lived Assets and Equity Method Investments: CMS Energy and Consumers perform tests of impairment if certain triggering events occur that indicate the carrying amount of an asset may not be recoverable or that there has been a decline in value that may be other than temporary.

CMS Energy and Consumers evaluate long-lived assets held in use for impairment by calculating the undiscounted future cash flows expected to result from the use of the asset and its eventual disposition. If the undiscounted future cash flows are less than the carrying amount, CMS Energy and Consumers recognize an impairment loss equal to the amount by which the carrying amount exceeds the fair value. CMS Energy and Consumers estimate the fair value of the asset using quoted market prices, market prices of similar assets, or discounted future cash flow analyses.

Impairment of Equity Method Investments

CMS Energy also assesses equity method investments for impairment whenever there has been a decline in value that is other than temporary. This assessment requires CMS Energy to determine the fair value of the equity method investment. CMS Energy determines fair value using valuation methodologies, including discounted cash flows, and assesses the ability of the investee to sustain an earnings capacity that justifies the carrying amount of the investment. CMS Energy records an impairment if the fair value is less than the carrying amount and the decline in value is considered to be other than temporary.

Investment Tax Credits

Investment Tax Credits: CMS Energy and its subsidiaries use the flow-through method of accounting for investment tax credits. Under the flow-through method, the credit is recognized as a reduction to income tax expense when the related plant, property, and equipment is placed into service. For its regulated utility assets, Consumers amortizes its investment tax credits over the life of the related property in accordance with regulatory treatment.

Inventory - Gas and Coal

Inventory: CMS Energy and Consumers use the weighted-average cost method for valuing working gas, recoverable base gas in underground storage facilities, and materials and supplies inventory. CMS Energy

and Consumers also use this method for valuing coal inventory, and they classify these amounts as generating plant fuel stock on their consolidated balance sheets.

Inventory - RECs and Emission Allowances

CMS Energy and Consumers account for RECs and emission allowances as inventory and use the weighted-average cost method to remove amounts from inventory. RECs and emission allowances are used to satisfy compliance obligations related to the generation of power. CMS Energy and Consumers classify these amounts within other assets on their consolidated balance sheets.

Inventory - Impairment

CMS Energy and Consumers evaluate inventory for impairment as required to ensure that its carrying value does not exceed the lower of cost or net realizable value.

MISO Transactions

MISO Transactions: MISO requires the submission of hourly day-ahead and real-time bids and offers for energy at locations across the MISO region. CMS Energy and Consumers account for MISO transactions on a net hourly basis in each of the real-time and day-ahead markets, netted across all MISO energy market locations. CMS Energy and Consumers record net hourly purchases in purchased and interchange power and net hourly sales in operating revenue on their consolidated statements of income. They record net billing adjustments upon receipt of settlement statements, record accruals for future net purchases and sales adjustments based on historical experience, and reconcile accruals to actual expenses and sales upon receipt of settlement statements.

Property Taxes

Property Taxes: Property taxes are based on the taxable value of CMS Energy’s and Consumers’ real and personal property assessed by local taxing authorities. CMS Energy and Consumers record property tax expense over the fiscal year of the taxing authority for which the taxes are levied. The deferred property tax balance represents the amount of CMS Energy’s and Consumers’ accrued property tax that will be recognized over future governmental fiscal periods.

Other: For additional accounting policies, see:

Capitalization

Capitalization: CMS Energy and Consumers record plant, property, and equipment at original cost when placed into service. The cost includes labor, material, applicable taxes, overhead such as pension and other benefits, and AFUDC, if applicable. Consumers’ plant, property, and equipment is generally recoverable through its general ratemaking process.

Software: CMS Energy and Consumers capitalize the costs to purchase and develop internal-use computer software. These costs are expensed evenly over the estimated useful life of the internal-use computer software. If computer software is integral to computer hardware, then its cost is capitalized and depreciated with the hardware.

Plant Retirement and Abandonment

With the exception of utility property for which the remaining book value has been securitized, mothballed utility property stays in rate base and continues to be depreciated at the same rate as before the mothball period. When utility property is retired or otherwise disposed of in the ordinary course of business, Consumers records the original cost to accumulated depreciation, along with associated cost of removal, net of salvage. CMS Energy and Consumers recognize gains or losses on the retirement or disposal of non‑regulated assets in income. Consumers records cost of removal collected from customers, but not spent, as a regulatory liability.

AFUDC

AFUDC: Consumers capitalizes AFUDC on regulated major construction projects. AFUDC represents the estimated cost of debt and authorized return-on-equity funds used to finance construction additions. Consumers records the offsetting credit as a reduction of interest for the amount representing the borrowed funds component and as other income for the equity funds component on the consolidated statements of income. When construction is completed and the property is placed in service, Consumers depreciates and recovers the capitalized AFUDC from customers over the life of the related asset.

Planned Major Maintenance Activities

CMS Energy and Consumers record property repairs and minor property replacement as maintenance expense. CMS Energy and Consumers record planned major maintenance activities as operating expense unless the cost represents the acquisition of additional long-lived assets or the replacement of an existing long-lived asset.

Lessee

CMS Energy and Consumers lease various assets from third parties, including coal-carrying railcars, real estate, service vehicles, and gas pipeline capacity. In addition, CMS Energy and Consumers account for several of their PPAs as leases.

CMS Energy and Consumers do not record right-of-use assets or lease liabilities on their consolidated balance sheets for rentals with lease terms of 12 months or less, most of which are for the lease of real estate and service vehicles. Lease expense for these rentals is recognized on a straight-line basis over the lease term.

CMS Energy and Consumers include future payments for all renewal options, fair market value extensions, and buyout provisions reasonably certain of exercise in their measurement of lease right-of-use assets and lease liabilities. In addition, certain leases for service vehicles contain end-of-lease adjustment clauses based on proceeds received from the sale or disposition of the vehicles. CMS Energy and Consumers also include executory costs in the measurement of their right-of-use assets and lease liabilities, except for maintenance costs related to their coal-carrying railcar leases.

Most of Consumers’ PPAs contain provisions at the end of the initial contract terms to renew the agreements annually under mutually agreed‑upon terms at the time of renewal. Energy and capacity payments that vary depending on quantities delivered are recognized as variable lease costs when incurred. Consumers accounts for a PPA with one of CMS Energy’s equity method subsidiaries as a finance lease.

Asset Retirement Obligations

CMS Energy and Consumers record the fair value of the cost to remove assets at the end of their useful lives, if there is a legal obligation to remove them. If a reasonable estimate of fair value cannot be made in the period in which the ARO is incurred, such as for assets with indeterminate lives, the liability is recognized when a reasonable estimate of fair value can be made. CMS Energy and Consumers have not recorded liabilities associated with the closure of certain gas wells that have an indeterminate life. CMS Energy and Consumers have not recorded liabilities for assets that have immaterial cumulative disposal costs, such as substation batteries.

CMS Energy and Consumers calculate the fair value of ARO liabilities using an expected present-value technique that reflects assumptions about costs and inflation, and uses a credit-adjusted risk-free rate to discount the expected cash flows. CMS Energy’s ARO liabilities are primarily at Consumers.

Retirement Benefits - Pension

The mortality assumption for benefit obligations was based on the Pri-2012 Mortality Table, with improvement scale MP-2021. The mortality assumption for net periodic benefit cost was based on the Pri-2012 Mortality Table, with improvement scale MP-2021 for 2023 and 2022 and improvement scale MP-2020 for 2021.

2The discount rate reflects the rate at which benefits could be effectively settled and is equal to the equivalent single rate resulting from a yield-curve analysis. This analysis incorporated the projected benefit payments specific to CMS Energy’s and Consumers’ DB Pension Plans and OPEB Plan and the yields on high-quality corporate bonds rated Aa or better.

3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023.

4CMS Energy and Consumers have elected to use a full-yield-curve approach in the estimation of service cost and interest cost; this approach applies individual spot rates along the yield curve to future projected benefit payments based on the time of payment.

5CMS Energy and Consumers determined the long-term rate of return using historical market returns, the present and expected future economic environment, the capital market principles of risk and return, and the expert opinions of individuals and firms with financial market knowledge. CMS Energy and Consumers considered the asset allocation of the portfolio in forecasting the future expected total return of the portfolio. The goal was to determine a long-term rate of return that could be incorporated into the planning of future cash flow requirements in conjunction with the change in the liability. Annually, CMS Energy and Consumers review for reasonableness and appropriateness the forecasted returns for various classes of assets used to construct an expected return model. CMS Energy’s and Consumers’ expected long-term rate of return on the assets of the DB Pension Plans was 7.20 percent in 2023. The actual return (loss) on the assets of the DB Pension Plans was 12.6 percent in 2023, (15.9) percent in 2022, and 12.0 percent in 2021.

CMS Energy and Consumers amortize net gains and losses in excess of ten percent of the greater of the PBO or the MRV over the average remaining service period for DB Pension Plan A and the OPEB Plan and over the average remaining life expectancy of participants for DB Pension Plan B. For DB Pension Plan A, the estimated period of amortization of gains and losses was eight years for the years ended

December 31, 2023, 2022, and 2021. For DB Pension Plan B, the estimated period of amortization of gains and losses was 17 years for the year ended December 31, 2023, and 18 years for the years ended December 31, 2022 and 2021. For the OPEB Plan, the estimated amortization period was nine years for the years ended December 31, 2023, 2022, and 2021.

Prior service cost (credit) amortization is established in the year in which the prior service cost (credit) first occurred, and is based on the same amortization period for all future years until the prior service cost (credit) is fully amortized. CMS Energy and Consumers had new prior service costs for OPEB in 2020. The estimated period of amortization of these new prior service costs is eight years.

CMS Energy and Consumers determine the MRV for the assets of the DB Pension Plans as the fair value of plan assets on the measurement date, adjusted by the gains or losses that will not be admitted into the MRV until future years. CMS Energy and Consumers reflect each year’s gain or loss in the MRV in equal amounts over a five‑year period beginning on the date the original amount was determined. CMS Energy and Consumers determine the MRV for OPEB Plan assets as the fair value of assets on the measurement date.

Retirement Benefits - Nonpension

3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023.

Income taxes

CMS Energy and its subsidiaries file a consolidated U.S. federal income tax return as well as a Michigan Corporate Income Tax return for the unitary business group and various other state unitary group combined income tax returns. Income taxes are allocated based on each company’s separate taxable income in accordance with the CMS Energy tax sharing agreement.

Accounts Receivable

Accounts Receivable and Unbilled Revenues: Accounts receivable comprise trade receivables and unbilled receivables. CMS Energy and Consumers record their accounts receivable at cost less an allowance for uncollectible accounts. The allowance is increased for uncollectible accounts expense and decreased for account write-offs net of recoveries. CMS Energy and Consumers establish the allowance based on historical losses, management’s assessment of existing economic conditions, customer payment trends, and reasonable and supported forecast information. CMS Energy and Consumers assess late payment fees on trade receivables based on contractual past-due terms established with customers. Accounts are written off when deemed uncollectible, which is generally when they become six months past due.

Consolidation, Variable Interest Entity

Newport Solar Holdings, NWO Holdco, Aviator Wind Equity Holdings, and Aviator Wind are VIEs. In accordance with the associated limited liability company agreements, the tax equity investors are guaranteed preferred returns from these entities. However, NorthStar Clean Energy manages and controls the entities’ operating activities. As a result, NorthStar Clean Energy is the primary beneficiary, as it has the power to direct the activities that most significantly impact the economic performance of the companies, as well as the obligation to absorb losses or the right to receive benefits from the companies.CMS Energy has variable interests in T.E.S. Filer City, Grayling, Genesee, and Craven. While CMS Energy owns 50 percent of each partnership, it is not the primary beneficiary of any of these partnerships because decision making is shared among unrelated parties, and no one party has the ability to direct the activities that most significantly impact the entities’ economic performance, such as operations and maintenance, plant dispatch, and fuel strategy. The partners must agree on all major decisions for each of the partnerships.

Consumers Energy Company

Significant Accounting Policies [Line Items]

Principles of Consolidation

Use of Estimates

Use of Estimates: CMS Energy and Consumers are required to make estimates using assumptions that may affect reported amounts and disclosures. Actual results could differ from those estimates.

Cash and Cash Equivalents

Restricted Cash and Cash Equivalents

Contingencies

Debt Issuance Costs, Discounts, Premiums, and Refinancing Costs

Derivative Instruments

commodity at a contracted price. Most of these contracts are not subject to derivative accounting for one or more of the following reasons:

•they do not have a notional amount (that is, a number of units specified in a derivative instrument, such as MWh of electricity or bcf of natural gas)

•they qualify for the normal purchases and sales exception

•they cannot be net settled due in part to the absence of an active market for the commodity

Impairment of Long-Lived Assets

Investment Tax Credits

Inventory - Gas and Coal

and Consumers also use this method for valuing coal inventory, and they classify these amounts as generating plant fuel stock on their consolidated balance sheets.

Inventory - RECs and Emission Allowances

Inventory - Impairment

CMS Energy and Consumers evaluate inventory for impairment as required to ensure that its carrying value does not exceed the lower of cost or net realizable value.

MISO Transactions

Property Taxes

Other: For additional accounting policies, see:

Government Assistance

Renewable Energy Grant: In 2013, Consumers received a $69 million renewable energy grant for Lake Winds® Energy Park, which began operations in 2012. This grant reduces Consumers’ cost of complying with Michigan’s renewable portfolio standard and, accordingly, reduces the overall renewable energy surcharge to be collected from customers. The regulatory liability recorded for the grant will be amortized over the life of Lake Winds® Energy Park. Consumers presents the amortization as a reduction to maintenance and other operating expenses on its consolidated statements of income.

Capitalization

Plant Retirement and Abandonment

AFUDC

Regulatory Depreciation and Amortization

Consumers depreciates utility property on an asset-group basis, in which it applies a single MPSC-approved depreciation rate to the gross investment in a particular class of property within the electric and gas segments. Consumers performs depreciation studies periodically to determine appropriate group lives.

Planned Major Maintenance Activities

Lessee

Asset Retirement Obligations

Retirement Benefits - Pension

3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023.

Retirement Benefits - Nonpension

3The DB SERP no longer requires rate of compensation increase as the last active participant retired in 2023.

Income taxes

Consumers Utility Revenue

Consumers Utility Revenue: Consumers recognizes revenue primarily from the sale of electric and gas utility services at tariff-based rates regulated by the MPSC. Consumers’ customer base consists of a mix of residential, commercial, and diversified industrial customers. Consumers’ tariff-based sales performance obligations are described below.

•Consumers has performance obligations for the service of standing ready to deliver electricity or natural gas to customers, and it satisfies these performance obligations over time. Consumers recognizes revenue at a fixed rate as it provides these services. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of Consumers’ service to stand ready to deliver.

•Consumers has performance obligations for the service of delivering the commodity of electricity or natural gas to customers, and it satisfies these performance obligations upon delivery. Consumers recognizes revenue at a price per unit of electricity or natural gas delivered, based on the tariffs established by the MPSC. These arrangements generally do not have fixed terms and remain in effect as long as the customer consumes the utility service. The rates are set by the MPSC through the rate-making process and represent the stand-alone selling price of a bundled product comprising the commodity, electricity or natural gas, and the service of delivering such commodity.

In some instances, Consumers has specific fixed-term contracts with large commercial and industrial customers to provide electricity or gas at certain tariff rates or to provide gas transportation services at contracted rates. The amount of electricity and gas to be delivered under these contracts and the associated future revenue to be received are generally dependent on the customers’ needs. Accordingly, Consumers recognizes revenues at the tariff or contracted rate as electricity or gas is delivered to the customer. Consumers also has other miscellaneous contracts with customers related to pole and other property rentals, appliance service plans, and utility contract work. Generally, these contracts are short term or evergreen in nature.

Accounts Receivable

Unbilled Revenues

Consumers’ customers are billed monthly in cycles having billing dates that do not generally coincide with the end of a calendar month. This results in customers having received electricity or natural gas that they have not been billed for as of the month-end. Consumers estimates its unbilled revenues by applying an average billed rate to total unbilled deliveries for each customer class.

Alternative-revenue Programs

Alternative‑revenue Programs: Consumers accounts for its energy waste reduction incentive mechanism and financial compensation mechanism as alternative-revenue programs. Consumers recognizes revenue related to the energy waste reduction incentive as soon as energy savings exceed the annual targets established by the MPSC and recognizes revenue related to the financial compensation mechanism as payments are made on MPSC-approved PPAs. For additional information on these mechanisms, see Note 2, Regulatory Matters.

Consumers does not reclassify revenue from its alternative-revenue program to revenue from contracts with customers at the time the amounts are collected from customers.