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Item 8. Financial Statements and Supplementary Data

2025-02-21 compared with 2024-02-16 · 356 added, 388 removed, 1786 unchanged (29% of the section changed)

27 unchanged sentences

The regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital.

Regulatory assets represent incurred costs that have been deferred and are probable of recovery in future customer rates.

Regulatory liabilities represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred.

Regulatory assets generally represent incurred costs that have been deferred and are probable of recovery in future customer rates.

Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred.

The Company’s regulatory assets and regulatory liabilities are recognized in accordance with the rulings of the regulatory agencies.

11 unchanged sentences

• We read relevant regulatory orders, interpretations, filings made by the Company or its stakeholders, and other publicly available information issued by the regulatory agencies that pertain to the Company.

We evaluated the external information and assessed whether there are matters in such information that would be contradictory to management’s assertion of probability of recovery of certain regulatory assets or refund of regulatory liabilities.

• We inspected minutes of the board of directors and other committees of the Company, regulatory orders and other filings with the regulatory agencies to identify evidence that may contradict management’s assertion regarding probability of abandonment or that may have an impact on the recorded balances.

20 unchanged sentences

Other operation and maintenance:

Asset valuation charge for IPL’s Lansing Generating Station 60 — —

Other 676 675 704

Depreciation and amortization 772 676 671

6 unchanged sentences

Allowance for funds used during construction ( 75 ) ( 100 ) ( 60 )

Other ( 3 ) 3 6

Total other (income) and deductions 310 236 220

1 unchanged sentence

Income tax expense (benefit) ( 114 ) 4 22

Net income 703 686 674

Preferred dividend requirements of Interstate Power and Light Company — — 15

Net income attributable to Alliant Energy common shareowners $ 690 $ 703 $ 686

65 unchanged sentences

Deferred tax expense (benefit) and tax credits ( 117 ) 14 13

Equity component of allowance for funds used during construction ( 74 ) ( 44 ) ( 18 )

Asset valuation charge for IPL’s Lansing Generating Station 60 — —

Other ( 22 ) ( 39 ) ( 17 )

1 unchanged sentence

Accounts receivable ( 547 ) ( 414 ) ( 672 )

Materials and supplies ( 62 ) ( 27 ) ( 13 )

Regulatory assets 70 24 ( 108 )

2 unchanged sentences

Regulatory liabilities ( 103 ) ( 149 ) 22

Derivative liabilities 19 70 ( 17 )

Deferred income taxes (a) 259 84 4

13 unchanged sentences

Proceeds from issuance of common stock, net 23 246 25

Payments to redeem cumulative preferred stock of IPL — — ( 200 )

Proceeds from issuance of long-term debt 1,613 1,455 1,338

7 unchanged sentences

Supplemental cash flows information:

Cash (paid) refunded during the period for:

Cash (paid) received during the period for:

Interest ($ 434 ) ($ 378 ) ($ 311 )

4 unchanged sentences

Beneficial interest obtained in exchange for securitized accounts receivable $ 163 $ 216 $ 185

(a) 2023 includes $ 98 million of proceeds from renewable tax credits transferred to other corporate taxpayers

(a) 2024 and 2023 include $ 216 million and $ 98 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers

Refer to accompanying Combined Notes to Consolidated Financial Statements.

2 unchanged sentences

CONSOLIDATED STATEMENTS OF EQUITY

Total Alliant Energy Common Equity

Accumulated Shares in Cumulative

Additional Other Deferred Preferred

Common Paid-In Retained Comprehensive Compensation Stock Total

Stock Capital Earnings Income (Loss) Trust of IPL Equity

Accumulated Shares in

Additional Other Deferred Total

Common Paid-In Retained Comprehensive Compensation Common

Stock Capital Earnings Income Trust Equity

(in millions)

5 unchanged sentences

Equity-based compensation plans and other 3 1 ( 1 ) 3

Redemption of IPL’s cumulative preferred stock ( 200 ) ( 200 )

Other comprehensive income, net of tax 1 1

Ending balance 3 2,777 3,509 — ( 13 ) 6,276

2 unchanged sentences

( 456 ) ( 456 )

Shareowner Direct Plan issuances 25 25

At-the-market offering program, net and Shareowner Direct Plan issuances 246 246

Equity-based compensation plans and other 7 7

Other comprehensive income, net of tax 1 1

Ending balance 3 3,030 3,756 1 ( 13 ) 6,777

2 unchanged sentences

( 492 ) ( 492 )

At-the-market offering program, net and Shareowner Direct Plan issuances 246 246

Shareowner Direct Plan issuances 23 23

Equity-based compensation plans and other 7 ( 1 ) 6

Other comprehensive income, net of tax 1 1

Ending balance $ 3 $ 3,060 $ 3,954 $ 1 ($ 14 ) $ 7,004

29 unchanged sentences

The regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital.

Regulatory assets represent incurred costs that have been deferred and are probable of recovery in future customer rates.

Regulatory liabilities represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred.

Regulatory assets generally represent incurred costs that have been deferred and are probable of recovery in future customer rates.

Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred.

The Company’s regulatory assets and regulatory liabilities are recognized in accordance with the rulings of the regulatory agencies.

11 unchanged sentences

• We evaluated the Company’s disclosures related to the impacts of rate regulation and regulatory developments, including disclosures related to certain regulatory balances recorded.

18 unchanged sentences

Other operation and maintenance:

Asset valuation charge for IPL’s Lansing Generating Station 60 — —

Other 358 353 369

Depreciation and amortization 404 388 381

5 unchanged sentences

Allowance for funds used during construction ( 43 ) ( 21 ) ( 11 )

Other ( 12 ) 2 6

Total other (income) and deductions 122 136 143

2 unchanged sentences

Net income $ 362 $ 366 $ 360

Preferred dividend requirements — — 15

Net income available for common stock $ 366 $ 360 $ 350

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of IPL’s common stock outstanding during the periods presented.

22 unchanged sentences

Current maturities of long-term debt $ 300 $ 500

Commercial paper 50 —

Accounts payable 263 262

Accounts payable to associated companies 47 51

Accrued taxes 77 50

1 unchanged sentence

Regulatory liabilities 54 72

Other 101 141

Total current liabilities 928 1,025

25 unchanged sentences

Depreciation and amortization 404 388 381

Deferred tax expense (benefit) and tax credits ( 91 ) 8 ( 13 )

Asset valuation charge for IPL’s Lansing Generating Station 60 — —

Other ( 12 ) ( 10 ) ( 8 )

1 unchanged sentence

Accounts receivable ( 544 ) ( 437 ) ( 611 )

Materials and supplies ( 39 ) ( 13 ) ( 7 )

Regulatory assets ( 2 ) 58 56

2 unchanged sentences

Regulatory liabilities ( 61 ) ( 92 ) 53

Derivative liabilities ( 16 ) 42 ( 8 )

Deferred income taxes (a) 178 36 ( 24 )

10 unchanged sentences

Capital contributions from parent 325 80 —

Payments to redeem cumulative preferred stock — — ( 200 )

Proceeds from issuance of long-term debt 643 296 —

Payments to retire long-term debt ( 500 ) — —

Net change in commercial paper 50 — —

Other ( 15 ) 7 4

4 unchanged sentences

Supplemental cash flows information:

Cash (paid) refunded during the period for:

Cash (paid) received during the period for:

Interest ($ 169 ) ($ 150 ) ($ 148 )

4 unchanged sentences

Beneficial interest obtained in exchange for securitized accounts receivable $ 163 $ 216 $ 185

(a) 2023 includes $ 76 million of proceeds from renewable tax credits transferred to other corporate taxpayers

(a) 2024 and 2023 includes $ 117 million and $ 76 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers

Refer to accompanying Combined Notes to Consolidated Financial Statements.

2 unchanged sentences

CONSOLIDATED STATEMENTS OF EQUITY

Total IPL Common Equity

Additional Cumulative

Common Paid-In Retained Preferred Total

Stock Capital Earnings Stock Equity

Additional Total

Common Paid-In Retained Common

Stock Capital Earnings Equity

(in millions)

Beginning balance $ 33 $ 2,807 $ 929 $ 3,769

Net income available for common stock 350 350

Net income 360 360

Common stock dividends ( 321 ) ( 321 )

Capital contributions from parent 50 50

Redemption of cumulative preferred stock ( 200 ) ( 200 )

Ending balance 33 2,807 968 3,808

Net income available for common stock 360 360

Net income 366 366

Common stock dividends ( 280 ) ( 280 )

Capital contributions from parent 80 80

Ending balance 33 2,887 1,054 3,974

Net income available for common stock 366 366

Net income 362 362

Common stock dividends ( 200 ) ( 200 )

31 unchanged sentences

The regulation of rates is premised on the full recovery of prudently incurred costs and a reasonable rate of return on invested capital.

Regulatory assets represent incurred costs that have been deferred and are probable of recovery in future customer rates.

Regulatory liabilities represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred.

Regulatory assets generally represent incurred costs that have been deferred and are probable of recovery in future customer rates.

Regulatory liabilities generally represent obligations to make refunds to customers or amounts collected in rates for which the costs have not yet been incurred.

The Company’s regulatory assets and regulatory liabilities are recognized in accordance with the rulings of the regulatory agencies.

11 unchanged sentences

28 unchanged sentences

Income before income taxes 356 405 381

Income tax expense (benefit) 60 66 ( 51 )

Income taxes 11 60 66

Net income $ 345 $ 345 $ 315

54 unchanged sentences

Depreciation and amortization 357 280 283

Deferred tax expense (benefit) and tax credits ( 13 ) 4 ( 79 )

Equity component of allowance for funds used during construction ( 23 ) ( 59 ) ( 36 )

1 unchanged sentence

Other changes in assets and liabilities:

Accounts receivable 23 ( 53 ) 3

Regulatory assets 72 ( 34 ) ( 163 )

3 unchanged sentences

Deferred income taxes (a) 84 50 32

Pension and other benefit obligations ( 19 ) ( 19 ) ( 63 )

Other ( 62 ) 33 ( 141 )

13 unchanged sentences

Net cash flows from financing activities 7 370 737

Net increase (decrease) in cash, cash equivalents and restricted cash 2 3 ( 1 )

Net increase in cash, cash equivalents and restricted cash 44 2 3

Cash, cash equivalents and restricted cash at beginning of period 7 5 2

1 unchanged sentence

Supplemental cash flows information:

Cash paid during the period for:

Cash (paid) received during the period for:

Interest ($ 163 ) ($ 146 ) ($ 111 )

3 unchanged sentences

Accrued capital expenditures $ 87 $ 217 $ 319

(a) 2023 includes $ 22 million of proceeds from renewable tax credits transferred to other corporate taxpayers

(a) 2024 and 2023 includes $ 99 million and $ 22 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers

Refer to accompanying Combined Notes to Consolidated Financial Statements.

2 unchanged sentences

CONSOLIDATED STATEMENTS OF EQUITY

Common Paid-In Retained Total

Additional Total

Common Paid-In Retained Common

Stock Capital Earnings Equity

4 unchanged sentences

Capital contributions from parent 530 530

Other ( 1 ) ( 1 )

Ending balance 66 2,233 1,192 3,491

2 unchanged sentences

Capital contributions from parent 245 245

Other ( 1 ) ( 1 )

Ending balance 66 2,478 1,353 3,897

17 unchanged sentences

IPL also sells electricity to wholesale customers in Minnesota, Illinois and Iowa, and is engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa.

In July 2025, IPL’s wholesale power agreement with Southern Minnesota Energy Cooperative will expire.

WPL’s financial statements include the accounts of WPL and its consolidated subsidiaries.

8 unchanged sentences

ATI, a wholly-owned subsidiary of AEF, holds all of Alliant Energy’s interest in ATC Holdings.

Corporate venture investments includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy.

Corporate venture investments includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help identify and research innovative technologies and business models within the emerging energy economy.

The non-utility wind farm includes a 50 % cash equity ownership interest in a 225 MW wind farm located in Oklahoma.

35 unchanged sentences

The Inflation Reduction Act of 2022 provides the ability to transfer renewable tax credits to other corporate taxpayers.

In 2023, IPL and WPL entered into agreements to transfer renewable tax credits from certain wind, solar and battery storage facilities to other corporate taxpayers in exchange for cash.

Alliant Energy, IPL and WPL have elected to record transfers of renewable tax credits as part of income taxes.

In 2023 and 2024, IPL and WPL entered into agreements to transfer renewable tax credits from certain wind, solar and energy storage facilities to other corporate taxpayers in exchange for cash.

Alliant Energy, IPL and WPL have elected to record transfers of renewable tax credits as part of income taxes, and cash received from the transfer of renewable tax credits is recorded in cash flows from operating activities.

For renewable tax credits subject to future transfer, a valuation allowance is recorded for the difference between the tax value of the credits and the expected sales price.

Renewable tax credits and any related valuation allowances are derecognized when control of the tax credits is transferred to other corporate taxpayers.

A majority of the differences between actual renewable tax credits and renewable tax credits used to determine rates are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers.

The cash received from the transfer of renewable tax credits is recorded in cash flows from operating activities.

Beginning October 1, 2024, IPL’s renewable energy rider was discontinued, and production tax credits, excluding production tax credits from the refurbishment of existing wind farms, are credited to IPL’s retail electric customers through its fuel-related cost recovery mechanism.

Investment tax credits resulting from IPL’s renewable generation and energy storage projects that are not yet included in base rates may be utilized to offset any revenue deficiency on an annual basis up to IPL’s return on common equity threshold;

any remaining investment tax credits, net of the cost of transferability, that are not used to offset any revenue deficiency, will be deferred by IPL and carried forward to offset any revenue deficiency in future years.

At WPL, pursuant to escrow treatment approved by the PSCW, the difference between actual solar and energy storage tax credits and the amount of renewable tax credits collected from customers as electric revenues is recognized in “Income taxes” in Alliant Energy’s and WPL’s income statements.

An offsetting amount is recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and WPL’s balance sheets until reflected in future billings to customers.

Refer to Notes 1 1 and 1 6 (d) for further discussion of the transfer of renewable tax credits to other corporate taxpayers, including related valuation allowances and indemnification requirements, respectively.

NOTE 1 (d) Cash, Cash Equivalents and Restricted Cash - Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days.

At December 31, 2023, Alliant Energy’s and IPL’s cash and cash equivalents included $ 45 million of money market fund investments, with a weighted average interest rate of 5 %.

At December 31, 2023 and 2022, Alliant Energy’s restricted cash related to requirements in Sheboygan Power, LLC’s debt agreement.

At December 31, 2024, Alliant Energy’s, IPL’s and WPL’s cash and cash equivalents included $ 52 million, $ 9 million, and $ 43 million, respectively, of money market fund investments, with weighted average interest rates of 4 %.

At December 31, 2024 and 2023, Alliant Energy’s restricted cash was not material.

NOTE 1 (e) Property, Plant and Equipment -

5 unchanged sentences

However, if regulators have approved recovery of the remaining net book value of property, plant and equipment that is retired early, or such approval by regulators is probable, the remaining net book value is reclassified from property, plant and equipment to regulatory assets upon retirement.

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Depreciation - IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions.

3 unchanged sentences

These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions.

Depreciation expense is included within the recoverable cost of service

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component of rates collected from customers.

Depreciation expense is included within the recoverable cost of service component of rates collected from customers.

The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:

5 unchanged sentences

Other 4.6 % 6.2 % 6.1 % 4.4 % 4.6 % 4.9 %

In October 2024, the IUC issued an order approving the implementation of updated depreciation rates for IPL effective October 1, 2024.

IPL estimates the new average rates of depreciation for its electric generation and electric distribution properties will be approximately 3.8 % and 3.0 %, respectively, during 2025.

AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting.

3 unchanged sentences

2024 2023 2022

IPL (Wind generation CWIP) 6.9 % 6.9 % 7.0 %

IPL (other CWIP) 7.0 % 7.0 % 7.2 %

IPL 7.0 % 7.0 % 7.0 %

WPL (retail jurisdiction) 7.4 % 7.4 % 7.0 %

1 unchanged sentence

In accordance with their respective regulatory commission decisions, IPL applies its AFUDC rates to 100 % of applicable CWIP balances, and WPL generally applies its AFUDC rates to 50 % of applicable CWIP balances and the remaining 50 % of applicable CWIP balances earns a return on such balances as part of its rate base.

WPL may apply its AFUDC rates to 100 % of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order, including the first and second solar generation CAs.

WPL may be authorized to apply its AFUDC rates to 100 % of the retail portion of the CWIP balances for construction projects requiring a CA or CPCN that were approved by the PSCW after its then most recent rate order.

Non-utility and Other Property -

12 unchanged sentences

As of December 31, 2024, the related amounts accrued for IPL and WPL were not material.

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IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by MISO.

3 unchanged sentences

Taxes Collected from Customers - Sales or various other taxes collected by certain of Alliant Energy’s subsidiaries on behalf of other agencies are recorded on a net basis and are not included in revenues.

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Other - Alliant Energy, IPL and WPL do not disclose the value of unsatisfied performance obligations for:

27 unchanged sentences

The cumulative effects of the under-/over-collection of these costs are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.

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WPL Retail - Electric transmission service expense is recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings.

3 unchanged sentences

Electric transmission service expense is allocated to and recovered from these customers based on a load ratio share computation.

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Cost of Gas Sold - Costs are incurred for the purchase, transportation and storage of natural gas to serve IPL’s and WPL’s gas customers and the costs associated with the natural gas delivered to customers are charged to “Cost of gas sold” in the income statements.

7 unchanged sentences

The cumulative effects of the under-/over-collection of these costs for IPL and WPL are recorded in regulatory assets or regulatory liabilities on the balance sheets until they are reflected in future billings to customers.

Renewable Energy Rider - IPL recovers a return of, as well as earns a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through a renewable energy rider.

Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, are also included in the rider.

This cost recovery mechanism provides for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits.

Changes in the under-/over-collection of these costs are recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements.

Renewable Energy Rider - IPL utilized a renewable energy rider prior to its discontinuation on October 1, 2024, effective with the IUC’s order for IPL’s retail electric rate review for the October 2024 through September 2025 Test Period.

Prior to October 1, 2024, IPL recovered a return of, as well as earned a return on, its wind generation placed in service in 2019 and 2020 from its retail electric customers through the renewable energy rider.

Other applicable costs and tax benefits associated with this wind generation, excluding operation and maintenance expenses, were also included in the rider.

This cost recovery mechanism provided for annual adjustments to electric rates charged to IPL’s retail electric customers for actual renewable energy costs and tax benefits.

Changes in the under-/over-collection of these costs were recognized in “Electric utility revenue” in Alliant Energy’s and IPL’s income statements.

The cumulative effects of the under-/over-collection of these costs for IPL are recorded in regulatory assets or regulatory liabilities on Alliant Energy’s and IPL’s balance sheets until they are reflected in future billings to customers.

Refer to Note 1(c) for further discussion of the treatment of IPL’s renewable tax credits for rate-making purposes.

NOTE 1 (h) Financial Instruments - Financial instruments are periodically used for risk management purposes to mitigate exposures to fluctuations in certain commodity prices, transmission congestion costs and interest rates.

8 unchanged sentences

If IPL or WPL are disallowed recovery of any portion of, or are only allowed a partial return on, the carrying value of their regulated property, plant and equipment that is under construction, has been recently completed or is probable of abandonment, or conclude it is probable recovery or a full return will be disallowed, then an impairment charge is recognized.

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Property, Plant and Equipment of Non-utility Operations - Property, plant and equipment of non-utility operations are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable.

7 unchanged sentences

The liability is accreted to its present value and the capitalized cost is depreciated over the useful life of the related asset.

Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated

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operations are recorded to regulatory assets on the balance sheets.

Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory assets on the balance sheets.

Revisions in estimated cash flows for IPL’s and WPL’s regulated operations are recorded as an increase or decrease to the ARO liability, with an offset to the asset cost, unless the asset is already retired and then the offset is recorded to regulatory assets or regulatory liabilities on the balance sheets.

3 unchanged sentences

Any gains or losses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory liabilities or regulatory assets on the balance sheets.

Refer to Note 13 for details of an ARO charge for steam assets at IPL in 2024.

NOTE 1 (k) Debt Issuance and Retirement Costs - Debt issuance costs and debt premiums or discounts are presented on the balance sheets as a direct adjustment to the carrying amount of the related debt liability, and are deferred and amortized over the expected life of each debt issue, considering maturity dates and, if applicable, redemption rights held by others.

21 unchanged sentences

Finance lease expense is comprised of depreciation and amortization, and interest expenses.

Finance lease assets related to leased land for solar generation are amortized on a straight-line basis over the lease term, and are accounted for as operating leases for rate-making purposes.

Finance lease assets related to leased land for solar generation are accounted for as operating leases for rate-making purposes.

All other finance lease assets are depreciated on a straight-line basis over the shorter of the useful life of the underlying asset or the lease term.

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REGULATORY MATTERS

4 unchanged sentences

At December 31, regulatory assets were comprised of the following items (in millions):

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Alliant Energy IPL WPL

1 unchanged sentence

Tax-related $ 989 $ 934 $ 870 $ 831 $ 119 $ 103

AROs 401 194 281 160 120 34

Pension and OPEB costs 315 347 157 171 158 176

Assets retired early 180 273 168 259 12 14

AROs 194 151 160 110 34 41

Commodity cost recovery 68 120 2 12 66 108

Derivatives 60 102 15 34 45 68

Non-service pension and OPEB costs 51 46 19 18 32 28

WPL’s Western Wisconsin gas distribution expansion investments 42 44 — — 42 44

3 unchanged sentences

At December 31, 2024, IPL and WPL had $ 199 million and $ 23 million, respectively, of regulatory assets that were not earning a return on investment.

IPL’s regulatory assets that were not earning a return consisted primarily of retired analog electric meters, emission allowances and costs for certain construction projects.

IPL’s regulatory assets that were not earning a return consisted primarily of the retired Lansing Generating Station, retired analog electric meters, emission allowances and costs for certain construction projects.

WPL’s regulatory assets that were not earning a return consisted primarily of costs for certain construction projects.

2 unchanged sentences

These temporary differences for IPL include the impacts of qualifying deductions for repairs expenditures, allocation of mixed service costs, and Iowa accelerated tax depreciation, which all contribute to lower current income tax expense during the first part of an asset’s useful life and higher current income tax expense during the latter part of an asset’s useful life.

Conversely, cost of removal obligations contribute to higher current income tax expense during the first part of an asset’s useful life and lower current income tax expense during the latter part of an asset’s useful life.

These regulatory assets will be recovered from customers in the future when these temporary differences reverse resulting in additional current income tax expense used to determine customers’ rates.

Refer to Note 11 for discussion of Iowa Tax Reform, which resulted in a decrease in Alliant Energy’s and IPL’s tax-related regulatory assets in 2024.

Pension and other postretirement benefits costs - The IUB, PSCW and FERC have authorized IPL and WPL to record the previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss on the balance sheets, as these amounts are expected to be recovered in future rates.

AROs - Alliant Energy, IPL and WPL believe it is probable that certain differences between expenses accrued for AROs related to their utility operations and expenses recovered currently in rates will be recoverable in future rates, and are deferring the differences as regulatory assets.

Refer to Note 13 for discussion of the recognition of additional ARO regulatory assets in 2024, substantially resulting from the enactment of the revised CCR Rule.

Pension and other postretirement benefits costs - The IUC, PSCW and FERC have authorized IPL and WPL to record the previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss on the balance sheets, as these amounts are expected to be recovered in future rates.

These regulatory assets will be increased or decreased as the net actuarial gains or losses, and prior service costs or credits, are subsequently amortized and recognized as a component of net periodic benefit costs.

4 unchanged sentences

Details regarding the recovery of the remaining net book value of these assets from IPL’s and WPL’s customers are as follows (dollars in millions):

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Entity Asset Retirement Date Regulatory Asset Balance as of Dec.

Recovery Regulatory Approval

IPL Lansing 2023 $ 216 Return of and return on remaining net book value through 2037 FERC and pending with the IUB (a)

IPL Analog electric meters 2019 20 Return of remaining net book value through 2028 IUB and FERC

IPL Sutherland Units 1 and 3 2017 12 Return of and return on remaining net book value through 2027 IUB and FERC

Kapp Unit 2 2018 11 Return of and return on remaining net book value through 2029 IUB and FERC

IPL Lansing 2023 $ 131 Return of (IUC and FERC) and return on (FERC) remaining net book value through 2037 (a) IUC and FERC (b)

IPL Analog electric meters 2019 15 Return of remaining net book value through 2028 IUC and FERC

IPL Sutherland Units 1 and 3 2017 15 Return of and return on remaining net book value through 2027 (a) IUC and FERC

Kapp Unit 2 2018 7 Return of and return on remaining net book value through 2029 (a) IUC and FERC

WPL Edgewater Unit 4 2018 12 Return of and return on remaining net book value through 2028 PSCW and FERC

(a) IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a request with the IUB for continued recovery of the remaining net book value of Lansing through 2037.

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In 2023, in conjunction with IPL's retirement of the Lansing Generating Station, IPL reclassified the remaining net book value of the associated AROs from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets.

(a) The remaining regulatory asset balances include differences between expected and actual cost of removal obligations.

(b) IPL was previously allowed a full recovery of and a full return on the Lansing Generation Station from both its retail and wholesale customers.

The IUC’s September 2024 order for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period includes a return of the remaining net book value of Lansing, but does not include a return on the remaining net book value of Lansing, effective October 1, 2024.

As a result, the return on the remaining net book value is no longer recoverable from IPL’s retail electric customers, and a pre-tax non-cash charge of $ 60 million was recorded to “Asset valuation charge for IPL’s Lansing Generating Station” in Alliant Energy’s and IPL’s income statements in 2024, with a corresponding decrease in Alliant Energy’s and IPL’s assets retired early regulatory assets.

Commodity cost recovery - Refer to Note 1(g) for details of IPL’s and WPL’s commodity cost recovery mechanisms.

The cost recovery mechanism for WPL’s retail electric customers is based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test periods and fuel monitoring ranges determined by the PSCW during each retail electric rate proceeding or in a separate fuel cost plan approval proceeding.

In 2021, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $ 37 million deferral as of December 31, 2022, which was collected in 2023 from its retail electric customers, plus interest.

In 2022, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $ 117 million deferral as of December 31, 2022, which WPL is collecting from October 2023 through December 2025 from its retail electric customers, plus interest ($ 12 million was collected in 2023).

In 2023, actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $ 34 million regulatory liability as of December 31, 2023, which is expected to be addressed in a future regulatory proceeding.

In 2023, WPL’s actual fuel-related costs fell outside these fuel monitoring ranges, resulting in a $ 34 million regulatory liability as of December 31, 2023, which was refunded in 2024 to its retail electric customers, plus interest.

Derivatives - In accordance with IPL’s and WPL’s fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recoverable from customers in the future after any losses are realized, and gains from derivative instruments are refundable to customers in the future after any gains are realized.

1 unchanged sentence

Refer to Note 1 4 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during 2024, which resulted in comparable changes to regulatory assets/liabilities on the balance sheets.

Non-service pension and OPEB costs - Non-service pension and OPEB costs are recorded to regulatory assets to reflect the impacts of rate-making, and are recovered from IPL’s and WPL’s electric and gas customers through depreciation expense based on the depreciation rates for plant in-service.

WPL’s Western Wisconsin gas distribution expansion investments - WPL made contributions in aid of construction to a third party for investments as part of its Western Wisconsin gas distribution expansion project.

1 unchanged sentence

IPL’s DAEC PPA Amendment - In 2020, IPL made a buyout payment of $ 110 million in exchange for shortening the term of its DAEC PPA by 5 years.

The buyout payment, including a return on, is being recovered from IPL’s retail and wholesale customers from 2021 through the end of 2025, and is currently being amortized to “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements.

The buyout payment, including a return on, is being recovered from IPL’s retail and wholesale customers from 2021 through 2025, and is currently being amortized to “Electric production fuel and purchased power” in Alliant Energy’s and IPL’s income statements.

Regulatory Liabilities - At December 31, regulatory liabilities were comprised of the following items (in millions):

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Commodity cost recovery 17 48 12 13 5 35

WPL’s West Riverside liquidated damages 1 32 — — 1 32

Other 29 85 14 56 15 29

$ 1,028 $ 1,130 $ 546 $ 644 $ 482 $ 486

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Tax-related regulatory liabilities reduce revenue requirement calculations utilized in IPL’s and WPL’s respective rate proceedings.

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These rules limit the rate at which these tax benefits are allowed to be passed on to customers.

The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities was primarily due to tax benefits resulting from WPL electing investment tax credit treatment for its Cassville solar facility in 2024.

A majority of these benefits will be addressed in a future regulatory proceeding, with a portion of the benefits passed on to WPL’s electric customers in 2024 and 2025.

Cost of removal obligations - Alliant Energy, IPL and WPL collect in rates future removal costs for many assets that do not have associated AROs or that have removal costs in addition to AROs.

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Cash payments related to cost of removal obligations are included in “Other” in cash flows used for investing activities.

WPL’s West Riverside liquidated damages - Pursuant to terms included in the related West Riverside construction procurement contracts, WPL reached agreement with the contractor on liquidated damages in 2020.

A significant portion of the liquidated damages was settled by WPL offsetting amounts owed to the contractor that were previously withheld for

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payment, which were non-cash investing activities.

Pursuant to PSCW authorization, WPL’s amortization of liquidated damages related to West Riverside construction procurement contracts was used to offset increases in WPL’s retail electric 2022/2023 Test Period revenue requirement, resulting in decreases in regulatory liabilities on Alliant Energy’s and WPL’s balance sheets and decreases in depreciation and amortization expenses in Alliant Energy’s and WPL’s income statements in 2023.

Rate Reviews -

WPL’s Retail Electric and Gas Rate Reviews (2022/2023 Forward-looking Test Period) - In December 2021, the PSCW issued an order authorizing annual base rate increases of $ 114 million and $ 15 million for WPL’s retail electric and gas customers, respectively, covering the 2022/2023 forward-looking Test Period, which was based on a stipulated agreement between WPL and certain stakeholders.

The key drivers for the annual base rate increases include higher retail fuel-related costs in 2022, lower excess deferred income tax benefits in 2022 and 2023 and revenue requirement impacts of increasing electric and gas rate base, including investments in solar generation.

In addition, the PSCW authorized WPL to receive a recovery of and a return on the remaining net book value of Edgewater Unit 5 through 2023.

WPL's settlement extended, with certain modifications, an earnings sharing mechanism through 2023.

Retail electric rate changes were effective on January 1, 2022 and extended through the end of 2023.

Retail gas rate changes were effective on January 1, 2022 and extended through the end of 2022.

In December 2022, the PSCW issued an order authorizing an additional annual base rate increase of $ 9 million for WPL’s retail gas customers, covering the 2023 forward-looking Test Period, which reflects changes in weighted average cost of capital, updated depreciation rates and modifications to certain regulatory asset and regulatory liability amortizations.

These retail gas rate changes were effective on January 1, 2023 and extended through the end of 2023.

WPL’s Retail Electric and Gas Rate Reviews (2024/2025 Forward-looking Test Period) - In December 2023, the PSCW issued an order authorizing annual base rate increases of $ 49 million and $ 13 million for WPL’s retail electric and gas customers, respectively, effective January 1, 2024, for the 2024 forward-looking Test Period.

The PSCW’s order also authorized WPL to implement an additional $ 60 million increase in annual rates for its retail electric customers, effective January 1, 2025, for the 2025 forward-looking Test Period.

The key drivers for the annual base rate increases include revenue requirement impacts of increasing electric and gas rate base, including investments in solar generation and energy storage.

In addition, the PSCW’s order extended, with certain modifications, an earnings sharing mechanism through the end of 2025.

The PSCW also authorized WPL to defer the incremental under-/over-collection of solar and energy storage renewable tax credits that are outside of the approved amounts, which are included in the tax-related lines of the regulatory assets and regulatory liabilities tables above.

Refer to Note 3 for discussion of PSCW orders approving deferral of, and the deferral of a return on, incremental solar generation construction costs in 2024 and 2025.

WPL’s Retail Fuel-related Rate Filing (2021 Forward-looking Test Period) - In 2023, WPL collected $ 37 million, plus interest, from its retail electric customers related to actual fuel-related costs for 2021 that were higher than fuel-related costs used to determine rates for such period.

IPL’s Retail Electric and Gas Rate Reviews (October 2024 through September 2025 Forward-looking Test Period) - In September 2024, the IUC issued an order authorizing annual base rate increases of $ 185 million for IPL’s retail electric customers, with customers receiving partially offsetting credits for the first 12 months through a tax benefit rider, and $ 10 million for IPL’s retail gas customers, for the October 2024 through September 2025 forward-looking Test Period.

Rate changes were effective October 1, 2024.

The IUC’s order also reflects the following:

• Electric earnings sharing mechanism beginning in calendar year 2025, where IPL would apply excess earnings to the remaining net book value of IPL’s highest earning asset with advance ratemaking principles (currently the Emery Generation Station) based on its authorized return on common equity;

• Investment tax credits resulting from renewable generation and energy storage projects may be utilized to offset any revenue deficiency on an annual basis up to IPL’s return on common equity threshold;

• Discontinuation of the renewable energy rider.

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PROPERTY, PLANT AND EQUIPMENT

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Electric plant:

Generation in service (a) $ 9,180 $ 8,060 $ 5,025 $ 4,962 $ 4,155 $ 3,098

Generation in service (a)(b) $ 11,156 $ 9,180 $ 5,924 $ 5,025 $ 5,232 $ 4,155

Distribution in service 7,811 7,314 4,344 4,091 3,467 3,223

Other in service 595 567 385 356 210 211

Anticipated to be retired early (b) 1,629 2,103 — 491 1,629 1,612

Anticipated to be retired early (c) 784 1,629 — — 784 1,629

Total electric plant 20,346 18,690 10,653 9,472 9,693 9,218

Gas plant in service 1,863 1,791 981 951 882 840

Other plant in service 653 624 411 402 242 222

Accumulated depreciation (b) ( 5,924 ) ( 5,690 ) ( 3,180 ) ( 3,149 ) ( 2,744 ) ( 2,541 )

Other plant in service (d) 734 653 456 411 278 242

Accumulated depreciation (c) ( 6,229 ) ( 5,924 ) ( 3,360 ) ( 3,180 ) ( 2,869 ) ( 2,744 )

Net plant 16,714 15,210 8,730 7,654 7,984 7,556

Leased Sheboygan Falls Energy Facility, net (c) — — — — 79 15

Leased Sheboygan Falls Energy Facility, net (e) — — — — 74 79

Leased land for solar generation, net 189 172 53 33 136 139

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Non-utility and other:

Non-utility Generation, net (d) 68 71 — — — —

Corporate Services and other, net (e) 455 423 — — — —

Non-utility Generation, net (f) 103 68 — — — —

Corporate Services and other, net (g) 475 455 — — — —

Total non-utility and other 578 523 — — — —

Total property, plant and equipment $ 18,701 $ 17,157 $ 9,336 $ 8,298 $ 8,861 $ 8,415

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(a) Alliant Energy and WPL currently expect estimated construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed amounts previously approved by the PSCW by approximately $ 180 million.

In February 2024, the PSCW issued an oral decision approving WPL’s deferral request to seek recovery of these costs in a future regulatory proceeding.

Alliant Energy and IPL currently expect the estimated construction costs associated with IPL’s 400 MW of new solar generation will exceed the cost target of $ 1,650 /kilowatt, including AFUDC and transmission upgrade costs among other costs, approved in the IUB’s advance rate-making principles by approximately 10 %.

Alliant Energy, IPL and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of December 31, 2023 given construction costs were reasonably and prudently incurred.

(b) In 2023, IPL retired Lansing and reclassified the remaining net book value of this EGU from property, plant and equipment to a regulatory asset on Alliant Energy’s and IPL’s balance sheets.

In 2020 and 2021, WPL received approval from MISO to retire Edgewater Unit 5, and Columbia Units 1 and 2, respectively.

WPL currently anticipates retiring Edgewater Unit 5 by June 1, 2025, and Columbia Units 1 and 2 by June 1, 2026.

Alliant Energy and WPL concluded that Edgewater Unit 5 and Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2023.

WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, Alliant Energy and WPL concluded that no disallowance was required as of December 31, 2023.

As of December 31, 2023, net book values were $ 504 million for Edgewater Unit 5, and $ 428 million for Columbia Units 1 and 2 in aggregate.

(c) Less accumulated amortization of $ 112 million and $ 106 million for WPL as of December 31, 2023 and 2022, respectively.

(a) Alliant Energy and WPL currently expect construction costs associated with WPL’s approximately 1,100 MW of new solar generation will exceed the construction cost estimates previously approved by the PSCW by approximately $ 205 million.

In 2024, the PSCW issued orders approving deferral of, and the deferral of a return on, the incremental solar generation construction costs in 2024 and 2025.

Alliant Energy and WPL concluded that there was not a probable disallowance of the higher rate base amounts as of December 31, 2024 given construction costs were reasonably and prudently incurred.

(b) In September 2024, the IUC approved IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period, which allows IPL to recover construction costs associated with its 400 MW of new solar generation, including AFUDC and transmission upgrade costs among other costs, above the original cost target of $ 1,650 /kilowatt up to $ 1,837.5 /kilowatt.

The costs up to the original cost target of $ 1,650 /kilowatt will earn a return on common equity of 10.25 %.

The costs between $ 1,650 /kilowatt and $ 1,837.5 /kilowatt will earn a return on common equity that is the same as other assets without advance rate-making principles, without having to establish that such costs were reasonably and prudently incurred.

Alliant Energy and IPL currently do not expect these construction costs will exceed $ 1,837.5 /kilowatt.

WPL currently plans to cease coal operations at Columbia Units 1 and 2 by the end of 2029, as well as evaluate the conversion of Columbia Unit 1 and/or Unit 2 to natural gas.

Alliant Energy and WPL concluded that Columbia Units 1 and 2 met the criteria to be considered probable of abandonment as of December 31, 2024.

As of December 31, 2024 and 2023, the net book value of Columbia Units 1 and 2 in aggregate was $ 413 million and $ 428 million, respectively.

As of December 31, 2023, WPL anticipated retiring Edgewater Unit 5 by June 1, 2025, and Alliant Energy and WPL concluded that Edgewater Unit 5 met the criteria to be considered probable of abandonment.

In May 2024, WPL announced updated plans to convert Edgewater Unit 5 to natural gas by 2028, subject to regulatory approvals.

As a result, as of December 31, 2024, Alliant Energy and WPL concluded that Edgewater Unit 5 no longer meets the criteria to be considered probable of abandonment.

WPL is currently allowed a full recovery of and a full return on these EGUs from both its retail and wholesale customers, and as a result, as of December 31, 2024, Alliant Energy and WPL concluded that no disallowance was probable.

(d) Includes IPL’s steam service assets, which are fully depreciated as of December 31, 2024.

IPL’s steam customers are each under contract through 2025 for taking minimum quantities of annual steam usage, with certain conditions.

(e) Less accumulated amortization of $ 116 million and $ 112 million for WPL as of December 31, 2024 and 2023, respectively.

Refer to Note 9 for discussion of WPL’s renewal of this lease in 2024.

For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.

(d) Less accumulated depreciation of $ 75 million and $ 71 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

(e) Less accumulated depreciation of $ 275 million and $ 269 million for Alliant Energy as of December 31, 2023 and 2022, respectively.

(f) Less accumulated depreciation of $ 78 million and $ 75 million for Alliant Energy as of December 31, 2024 and 2023, respectively.

(g) Less accumulated depreciation of $ 289 million and $ 275 million for Alliant Energy as of December 31, 2024 and 2023, respectively.

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AFUDC - AFUDC represents costs to finance construction additions, including a return on equity component and cost of debt component as required by regulatory accounting.

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Non-utility Generation - The Sheboygan Falls Energy Facility was placed in service in 2005 and is depreciated using the straight-line method over a 35 -year period.

Corporate Services and Other - Property, plant and equipment related to Corporate Services include a customer billing and information system for IPL and WPL and other computer software, and the corporate headquarters building located in Madison, Wisconsin.

The customer billing and information system is amortized using the straight-line method over a 12 -year period.

The majority of the remaining software is amortized over a 5 -year period.

Corporate Services and Other - Property, plant and equipment related to Corporate Services include computer software, and the corporate headquarters building located in Madison, Wisconsin.

The majority of the software is amortized over a 5 -year period.

Other property, plant and equipment include Travero assets (a short-line rail freight service in Iowa;

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All Corporate Services and Other property, plant and equipment are depreciated using the straight-line method over periods ranging from 5 to 30 years.

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JOINTLY-OWNED ELECTRIC UTILITY PLANT

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Louisa Unit 1 4.0 % 43 23 —

Columbia Units 1-2 53.5 % 818 361 6

Columbia Units 1-2 and Energy Storage System 53.5 % 859 378 6

West Riverside Energy Center and Solar Facility (a) 56.6 % 449 59 5

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Alliant Energy $ 2,496 $ 992 $ 45

(a) In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc.

acquired partial ownership interests in West Riverside.

The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.

(a) In 2023 and 2024, WEC Energy Group, Inc.

and Madison Gas and Electric Company acquired partial ownership interests in West Riverside.

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NOTE 5 (a) Accounts Receivable - Details for accounts receivable included on the balance sheets as of December 31 were as follows (in millions):

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In 2024, gross write-offs for accounts receivable were as follows (in millions):

Originated in 2022 Originated in 2023

Originated in 2023

Originated in 2024

Alliant Energy $ 12 $ 14

NOTE 5 (b) Sales of Accounts Receivable - IPL maintains a Receivables Agreement whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities.

The purchase commitment from the third party to which IPL sells its receivables expires in March 2024.

IPL currently expects to amend and extend the purchase commitment.

In March 2024, IPL amended and extended through March 2026 the purchase commitment from the third party to which it sells its receivables.

IPL pays a monthly fee to the third party that varies based on interest rates, limits on cash proceeds and cash amounts received from the third party.

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The limit on cash proceeds fluctuates between $ 5 million and $ 110 million, which IPL may change periodically throughout the year.

As of December 31, 2023, the limit on cash proceeds was $ 5 million and IPL had

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$ 4 million of available capacity under its sales of accounts receivable program.

As of December 31, 2024, the limit on cash proceeds was $ 110 million and IPL had $ 40 million of available capacity under its sales of accounts receivable program.

Cash proceeds are used by IPL to meet short-term financing needs, and cannot exceed the current limit or amount of receivables available for sale, whichever is less.

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Write-offs, net of recoveries 12 12 9

Effective January 2024, the limit on cash proceeds under the Receivables Agreement is $ 110 million.

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Unconsolidated Equity Investments - Alliant Energy’s unconsolidated investments accounted for under the equity method of accounting are as follows (in millions):

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ATC Holdco LLC holds Duke-American Transmission Company, LLC, a joint venture between Duke Energy Corporation and ATC, that owns electric transmission infrastructure in North America.

Refer to Note 17(g) for discussion of a reduction in earnings recorded in 2022 related to a court decision, which is currently expected to reduce the base return on equity authorized for MISO transmission owners, including ATC.

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Refer to Note 1 6 (g) for discussion of a reduction in earnings recorded in 2022 related to a court decision, and subsequent FERC order, which reduced the base return on equity authorized for MISO transmission owners, including ATC.

Non-utility Wind Farm in Oklahoma - The non-utility wind farm located in Oklahoma provides electricity to a third-party under a long-term PPA, and has both cash and tax equity ownership.

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Refer to Note 1 6 (d) for discussion of the guarantee.

Corporate Venture Investments - Alliant Energy has various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy.

Corporate Venture Investments - Alliant Energy has various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help identify and research innovative technologies and business models within the emerging energy economy.

COMMON EQUITY

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At-the-Market Offering Program - In December 2022, Alliant Energy filed a prospectus supplement to sell up to $ 225 million of its common stock through an at-the-market offering program.

As of December 31, 2023, Alliant Energy issued 4,372,561 shares of common stock through this program and received cash proceeds of $ 223 million, net of $ 2 million in commissions and fees.

In 2023, Alliant Energy issued 4,372,561 shares of common stock through this program and received cash proceeds of $ 223 million, net of $ 2 million in commissions and fees.

The proceeds from the issuances of common stock were used for general corporate purposes.

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Shareowner Direct Plan - Alliant Energy satisfies its requirements under the Shareowner Direct Plan (dividend reinvestment and stock purchase plan) by acquiring Alliant Energy common stock through original issue, rather than on the open market.

PREFERRED STOCK

In 2021, IPL redeemed all 8,000,000 outstanding shares of its 5.1 % cumulative preferred stock at the $ 25 per share par value for $ 200 million plus accrued and unpaid dividends up to the redemption date.

In 2021, Alliant Energy and IPL recorded a $ 5 million non-cash charge related to this transaction in “Preferred dividend requirements” in their income statements.

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NOTE 8 (a) Short-term Debt - Alliant Energy and its subsidiaries maintain committed bank lines of credit to provide short-term borrowing flexibility and back-stop liquidity for commercial paper outstanding.

At December 31, 2023, the short-term borrowing capacity under a single credit facility agreement totaled $ 1 billion ($ 450 million for Alliant Energy at the parent company level, $ 150 million for IPL and $ 400 million for WPL).

Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $ 500 million, $ 400 million and $ 500 million, respectively, within the $ 1 billion total commitment.

At December 31, 2024, the short-term borrowing capacity under a single credit facility agreement, which expires in December 2029, totaled $ 1.3 billion ($ 600 million for Alliant Energy at the parent company level, $ 300 million for IPL and $ 400 million for WPL).

Subject to certain conditions, Alliant Energy (at the parent company level), IPL and WPL may each reallocate and change its sublimit up to $ 1 billion, $ 400 million and $ 500 million, respectively, within the $ 1.3 billion total commitment.

Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper classified as short-term debt was as follows (dollars in millions):

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Amount outstanding $ 558 $ 475 $ 50 $ — $ 183 $ 318

Weighted average interest rates 5.5 % 4.6 % N/A N/A 5.4 % 4.5 %

Weighted average interest rates 4.5 % 5.5 % 4.6 % N/A 4.5 % 5.4 %

Available credit facility capacity $ 742 $ 525 $ 250 $ 150 $ 217 $ 82

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Weighted average interest rates 5.3 % 5.2 % 5.1 % 5.3 % 5.4 % 5.1 %

In January 2024, Alliant Energy, IPL and WPL extended their single credit facility agreement, which currently expires in December 2028, and reallocated credit facility capacity amounts to $ 350 million for Alliant Energy at the parent company level, $ 150 million for IPL and $ 500 million for WPL, within the $ 1 billion total commitment.

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300 300 — 300 300 —

6.45 %, due 2033

100 100 — 100 100 —

4.95 %, due 2034 (b)

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300 300 — 300 300 —

3.1 %, due 2051

5.45 %, due 2054 (b)

300 300 — — — —

3.25 % (Retired in 2024)

— — — 500 500 —

4,125 4,125 — 3,975 3,975 —

Debentures (a):

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600 — 600 600 — 600

4.95 % due 2033

300 — 300 300 — 300

5.375 %, due 2034 (c)

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575 — — 575 — —

AEF 5.4 % senior notes, due 2027 (with Alliant Energy as guarantor) (a)(f)

375 — — — — —

AEF 4.25 % senior notes, due 2028 (with Alliant Energy as guarantor) (a)

300 — — 300 — —

AEF 5.95 % senior notes, due 2029 (with Alliant Energy as guarantor) (a)(f)

AEF 5.95 % senior notes, due 2029 (with Alliant Energy as guarantor) (a)

300 — — 300 — —

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350 — — 350 — —

Sheboygan Power, LLC 5.06 % senior secured notes, due 2024 (secured by the Sheboygan Falls Energy Facility and related assets) (a)

AEF 3.75 % senior notes (with Alliant Energy as guarantor) (Retired in 2023)

AEF term loan credit agreement, 6 % at December 31, 2023 (with Alliant Energy as guarantor) (Retired in 2024) (d)

— — — 300 — —

Other, 1 % at December 31, 2023, due 2024 to 2025

Sheboygan Power, LLC 5.06 % senior secured notes (secured by the Sheboygan Falls Energy Facility and related assets) (Retired in 2024)

2,400 — — 2,034 — —

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Treasury rates at the time of redemption.

(b) In September 2023, IPL issued $ 300 million of 5.7 % senior debentures due 2033.

The net proceeds from the issuance were used to reduce cash amounts received from its sales of accounts receivable program, reduce commercial paper classified as long-term debt, for general corporate purposes and/or were placed in money market fund investments.

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(b) In September 2024, IPL issued $ 350 million of 4.95 % senior debentures due 2034 and $ 300 million of 5.45 % senior debentures due 2054.

A portion of the net proceeds was used for the retirement of IPL’s $ 500 million 3.25 % senior debentures, and the remainder of the net proceeds was used for general corporate purposes.

The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds was disbursed for the development and acquisition of its solar EGUs.

(d) In January 2023, AEF entered into a $ 300 million interest rate swap maturing in January 2026 to mitigate interest rate risk.

Under the terms of the swap, AEF exchanged a variable interest rate for a fixed interest rate of 3.93 % on a portion of its variable-rate term loan borrowings.

In December 2023, AEF retired the remaining $ 100 million variable-rate term loan borrowings.

Refer to Note 15 for additional information on the interest rate swap.

The debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds was disbursed for the development and acquisition of WPL’s solar EGUs.

(d) In March 2024, AEF entered into a $ 300 million variable rate term loan credit agreement, which amended and restated the term loan credit agreement that expired in March 2024, and retired the $ 300 million variable rate term loan set forth therein.

AEF’s restated agreement includes an option to increase the amount outstanding with one or more additional term loans in an aggregate amount not to exceed $ 100 million.

Refer to Note 1 4 for information on AEF’s related interest rate swap.

(e) Refer to “ Convertible Senior Notes ” below for additional information.

(f) In November 2023, AEF issued $ 300 million of 5.95 % senior notes due 2029.

The net proceeds from AEF’s issuance were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes.

(f) In June 2024, AEF issued $ 375 million of 5.4 % senior notes due 2027.

The net proceeds were used to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes.

(g) There were no significant sinking fund requirements related to the outstanding long-term debt.

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If Alliant Energy undergoes a fundamental change (as defined in the related Indenture), then, subject to certain conditions, holders of the Notes may require Alliant Energy to repurchase for cash all or any portion of its Notes at a fundamental change repurchase price equal to 100 % of the principal amount of the Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

As of December 31, 2023, the conditions allowing holders of the Notes to convert their Notes were not met, and as a result, the Notes were classified as “Long-term debt, net” on Alliant Energy’s balance sheet.

As of December 31, 2023, the net carrying amount of the Notes was $ 568 million, with unamortized debt issuance costs of $ 7 million, and the estimated fair value (Level 2) of the Notes was $ 572 million.

As of December 31, 2024, the conditions allowing holders of the Notes to convert their Notes were not met.

As of December 31, 2024 and 2023, the Notes were classified on Alliant Energy’s balance sheets as “Current maturities of long-term debt” and “Long-term debt, net,” respectively.

As of December 31, 2024 and 2023, the net carrying amount of the Notes was $ 571 million and $ 568 million , with unamortized debt issuance costs of $ 4 million and $ 7 million, and the estimated fair value (Level 2) of the Notes was $ 591 million and $ 572 million.

As of December 31, 2024, there were no shares of Alliant Energy’s common stock related to the potential conversion of the Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the Notes.

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Five-Year Schedule of Long-term Debt Maturities - At December 31, 2024, long-term debt maturities for 2025 through 2029 were as follows (in millions):

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Alliant Energy $ 600 $ 775 $ 675 $ 800 $ 950

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Fair Value of Long-term Debt - Refer to Note 1 5 for information on the fair value of long-term debt outstanding.

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In 2024, WPL renewed this financing lease through 2044.

This lease contains one remaining lease renewal period, which is not included in the finance lease obligation.

There are no lease renewal periods remaining.

For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s amounts below.

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Leased land for solar generation $ — $ — — $ — $ — —

— — 11 5 — 17

Other liabilities:

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Total finance lease liabilities $ 189 $ 53 $ 214 $ 172 $ 33 $ 228

Weighted average remaining lease term 33 years 29 years 27 years 34 years N/A 28 years

Weighted average discount rate 5 % 5 % 5 % 5 % N/A 5 %

Weighted average remaining lease term 31 years 28 years 28 years 33 years 29 years 27 years

Weighted average discount rate 5 % 5 % 5 % 5 % 5 % 5 %

Alliant Energy IPL WPL

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Total finance lease expense $ 8 $ 7 $ 3 $ 2 $ 1 $ — $ 14 $ 14 $ 13

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Finance lease liabilities arising from obtaining leased assets, which represent non-cash financing activities, were as follows (in millions):

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$ 20 $ 34 $ 20 $ 33 $ — $ 71

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Expected Maturities - As of December 31, 2024, expected maturities of lease liabilities were as follows (in millions):

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IPL’s and WPL’s retail electric and gas revenues include sales to residential, commercial and industrial customers.

IPL’s and WPL’s retail electric and gas customer prices are based on IPL’s and WPL’s cost of service and are determined through general rate review proceedings and various tariff filings with the IUB and PSCW, respectively.

Such tariff-based services provide electricity or gas to customers without a defined contractual term.

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freight brokerage services;

wind turbine blade recycling services;

and a rail-served warehouse in Iowa.

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Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

Disaggregation of revenues from contracts with customers is provided for each reportable segment (IPL and WPL), as well as by customer class within electric and gas sales, as follows (in millions):

Alliant Energy IPL WPL

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Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes.

In 2024, Alliant Energy’s and IPL’s effective income tax rates were impacted by the pre-tax non-cash charge of $ 60 million for IPL’s Lansing Generation Station discussed in Note 2 .

Alliant Energy IPL WPL

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Production tax credits ( 31 ) ( 17 ) ( 18 ) ( 46 ) ( 31 ) ( 34 ) ( 20 ) ( 7 ) ( 5 )

Investment tax credits ( 3 ) — — ( 2 ) — — ( 3 ) — —

Amortization of excess deferred taxes (Refer to Note 2 )

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Effect of rate-making on property-related differences ( 5 ) ( 4 ) ( 1 ) ( 10 ) ( 5 ) ( 1 ) ( 1 ) ( 3 ) ( 2 )

Adjustment for prior period taxes — 1 1 — 1 2 — — —

Other items, net 1 1 — ( 1 ) — 2 — 1 —

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Federal tax credits 2033-2044 605 426 166

Valuation Allowances - Refer to N ote 1 (c) for discussion of valuation allowances recorded in 2023 related to the expected transfer of renewable tax credits to other corporate taxpayers.

Valuation Allowances - Refer to N ote 1 (c) for discussion of valuation allowances related to the expected transfer of renewable tax credits to other corporate taxpayers.

Uncertain Tax Positions - At December 31, 2024, 2023 and 2022, there were no uncertain tax positions or penalties accrued related to uncertain tax positions.

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Iowa Tax Reform - In 2018, Iowa tax reform was enacted, resulting in a reduction in the Iowa income tax rate from 12 % to 9.8 %, effective January 1, 2021, and the elimination of the deduction for federal income taxes, effective January 1, 2022, for taxes related to 2020 and prior.

In March 2022, additional Iowa tax reform was enacted.

Annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if certain state income tax revenue triggers are satisfied.

Iowa Tax Reform - Pursuant to Iowa tax reform enacted in 2022, annually, and by each November 1, the Iowa Department of Revenue will establish corporate income tax rates for the next tax year based on net corporate income tax receipts for the prior tax year, and reduce such rates if the minimum receipt threshold is met.

These corporate income tax rate reductions are currently expected to occur over a period of several years, with a target corporate income tax rate of 5.5 %, compared to the 9.8 % Iowa corporate income tax rate in effect at the time the Iowa tax reform was enacted.

In September 2022 and September 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4 % effective January 1, 2023, and 7.1 % effective January 1, 2024, respectively.

In 2022 and 2023, the Iowa Department of Revenue announced an Iowa corporate income tax rate of 8.4 % effective January 1, 2023, and 7.1 % effective January 1, 2024, respectively.

Deferred tax assets and liabilities are measured at the enacted tax rate expected to be applied when temporary differences are to be realized or settled.

Given the announcements of the new Iowa corporate income tax rates, Alliant Energy’s and IPL’s deferred tax liabilities were remeasured in 2022 and 2023 based upon the new rates effective January 1, 2023 and January 1, 2024, which resulted in a $ 77 million and $ 74 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in 2022 and 2023, respectively.

The reduction in tax-related regulatory assets is expected to provide cost benefits to IPL’s customers in the future.

Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rates effective January 1, 2023 and January 1, 2024, which resulted in charges of $ 8 million and $ 10 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred income tax liabilities on Alliant Energy’s balance sheets in 2022 and 2023, respectively.

In addition, Iowa tax reform made Iowa state income taxes fully deductible for the purpose of determining Iowa state income tax obligations beginning with the 2023 tax year.

Alliant Energy reflected the deduction of the additional Iowa state income taxes in its 2023 Iowa state income tax return filed in 2024, which resulted in a $ 26 million reduction of Alliant Energy’s and IPL’s tax-related regulatory assets and a corresponding decrease in their deferred tax liabilities in 2024.

The reductions in tax-related regulatory assets are expected to provide cost benefits to IPL’s customers in the future.

Alliant Energy parent company’s deferred tax assets were remeasured based upon the new rates effective January 1, 2023 and January 1, 2024, and the deduction of Iowa state income taxes included in Alliant Energy’s 2023 Iowa state income tax return filed in 2024, which resulted in charges of $ 8 million, $ 10 million and $ 11 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred income tax liabilities on Alliant Energy’s balance sheets in 2022, 2023 and 2024, respectively.

Alliant Energy is currently unable to predict with certainty the timing or amount of any future rate reductions.

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For IPL and WPL, amounts below represent the amounts for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans.

Assumptions - The assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows:

Assumptions - The weighted-average assumptions for defined benefit pension and OPEB plans at the measurement date of December 31 were as follows:

Defined Benefit Pension Plans OPEB Plans

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Rate of compensation increase 3.75 % 3.30 % 3.30 % N/A N/A N/A

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Qualified Defined Benefit Pension Plan OPEB Plans

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Rate of compensation increase 3.50 % 3.30 % 3.30 % N/A N/A N/A

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Expected rate of return on plan assets - The expected rate of return on plan assets is based on projected asset class returns using target allocations.

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(c) Unrecognized net actuarial gains or losses in excess of 10% of the greater of the plans’ benefit obligations or assets are amortized over the average future service lives of plan participants, except for the Alliant Energy Cash Balance Pension Plan where gains or losses outside the 10% threshold are amortized over the time period the participants are expected to receive benefits.

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(d) Settlement losses related to payments made to retired executives of Alliant Energy and lump sum payments related to IPL’s and WPL’s qualified defined benefit pension plans.

In 2022, the majority of Alliant Energy’s, IPL’s, and WPL’s pension settlement losses were recognized as regulatory assets in accordance with regulatory treatment, and $ 7 million was included in “Other (income) and deductions” in Alliant Energy’s and IPL’s income statements related to IPL’s qualified defined benefit pension plan.

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Benefit Plan Assets and Obligations - A reconciliation of the funded status of qualified and non-qualified defined benefit pension and OPEB plans to the amounts recognized on the balance sheets at December 31 was as follows (in millions):

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Net actuarial loss $ 135 $ 148 $ — $ 3

Prior service credit — — — —

$ 148 $ 165 $ 3 $ 6

In 2023, actuarial losses related to benefit obligations for defined benefit pension plans were primarily due to decreases in the discount rates.

In 2022, actuarial gains related to benefit obligations for defined benefit pension and OPEB plans were primarily due to increases in the discount rates.

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Accumulated benefit obligations, aggregate amounts applicable to defined benefit pension and OPEB plans with accumulated benefit obligations in excess of plan assets, as well as defined benefit pension plans with projected benefit obligations in excess of plan assets as of the December 31 measurement date are as follows (in millions):

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Fair value of plan assets 715 732 N/A N/A

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Defined Benefit Pension Plans OPEB Plans

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Plans with accumulated benefit obligations in excess of plan assets:

Accumulated benefit obligations 377 379 65 68

Fair value of plan assets 352 344 61 58

Accumulated benefit obligations 362 377 N/A 65

Fair value of plan assets 340 352 N/A 61

Plans with projected benefit obligations in excess of plan assets:

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$ 95 $ 91 $ 89 $ 89 $ 88 $ 391

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IPL 2025 2026 2027 2028 2029 2030 - 2034

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$ 40 $ 37 $ 37 $ 36 $ 36 $ 167

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Investment Strategy for Plan Assets - Investment strategies for defined benefit pension and OPEB plan assets combine preservation of principal and prudent risk-taking to protect the integrity of plan assets, in order to meet the obligations to plan participants while minimizing benefit costs over the long term.

Investment risk of plan assets is mitigated through diversification, including equity, fixed income and global asset strategies.

Global asset strategies may include investments in global equity, global debt and currencies.

Defined Benefit Pension Plan Assets - The asset mix of defined benefit pension plans is governed by allocation targets.

Investment risk of plan assets is mitigated through an asset mix, which is governed by allocation targets.

The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges.

An overlay management service is also used to help maintain target allocations and meet liquidity needs.

The overlay manager is authorized to use derivative financial instruments to facilitate this service.

For separately managed accounts, prohibited investments include, but are not limited to, direct ownership of real estate, oil and gas limited partnerships, securities of the managers’ firms or affiliate firms, and Alliant Energy securities.

The allocations shown below exclude market exposure obtained through the overlay management service.

Defined Benefit Pension Plan Assets - Defined benefit pension plan assets have a long-term investment time horizon and are classified into return-seeking and liability-hedging portfolios.

The return-seeking portfolio includes:

public equities with different market capitalization, investment style and geography;

liquid alternative securities, which include hedge fund strategies;

and fixed income investments, which include, but are not limited to, high-yield bonds, emerging market debt, bank loans and private credit bonds.

The liability-hedging portfolio includes:

fixed-income investments including investment grade instruments of government and corporate issuers, as well as private placements and securitized assets;

and fixed income derivative contracts for liability and interest rate hedging positions.

At December 31, 2024, the current target ranges and actual allocations for the defined benefit pension plan assets were as follows:

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Allocation Allocation

Cash and equivalents 0 % - 5 % 2 %

Equity securities 47 % - 67 % 56 %

Global asset securities 0 % - 15 % 5 %

Fixed income securities 27 % - 47 % 37 %

Public equity securities 32 % - 49 % 44 %

Liquid alternative securities 0 % - 12 % 6 %

Return-seeking fixed income securities 4 % - 18 % 8 %

Liability-hedging fixed income securities (including cash and equivalents) 34 % - 53 % 42 %

Other Postretirement Benefits Plan Assets - OPEB plan assets are comprised of specific assets within certain defined benefit pension plans (401(h) assets) as well as assets held in VEBA trusts.

For VEBA trusts with assets greater than $ 5 million and the WPL 401(h) assets, the mix among asset classes is governed by allocation targets.

The asset allocation is monitored regularly, and appropriate steps are taken as needed to rebalance the assets within the prescribed ranges.

At December 31, 2023, the current target ranges and actual allocations for VEBA trusts with assets greater than $ 5 million and the WPL 401(h) assets were as follows:

For asset pools with a long-term investment time horizon, investments include public equities with different market capitalization, investment style and geography, and fixed income securities including investment grade instruments of government and corporate issuers.

At December 31, 2024, the current target ranges and actual allocations for assets with a long-term investment horizon were as follows:

Target Range Actual

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Cash and equivalents 0 % - 5 % 1 %

Equity securities 0 % - 55 % 36 %

Public equity securities 0 % - 40 % 27 %

Fixed income securities 40 % - 100 % 72 %

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Refer to Note 1 5 for discussion of levels within the fair value hierarchy.

Level 1 items include investments in securities held in registered investment companies and directly held equity securities, which are valued at the closing price reported in the active market in which the securities are traded.

Level 2 items include cash and equivalents and fixed income securities.

Cash and equivalents include money market fund investments and cash collateral supporting derivative financial instruments.

Fixed income securities include corporate and government bonds, which are valued at the closing price reported in the active market for similar assets in which the individual securities are traded or based on yields currently available on comparable securities of issuers with similar credit ratings.

Level 1 items include investments in securities held in registered investment companies, which are valued at the closing price reported in the active market in which the securities are traded.

Level 2 items include cash and equivalents consisting of money market fund investments and cash collateral supporting derivative financial instruments.

Certain investments that are measured at fair value using the net asset value practical expedient have not been classified in the fair value hierarchy.

These fair value amounts are included below to reconcile the fair value hierarchy to the respective total plan assets.

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At December 31, the fair values of qualified and non-qualified defined benefit pension plan assets were as follows (in millions):

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Accrued investment income — 2

Due to brokers, net (pending trades with brokers) ( 1 ) —

Total pension plan assets $ 715 $ 732

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Fair Level Level Level Fair Level Level Level

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Equity securities 20 20 — — 8 8 — —

Global asset securities — — — — 1 1 — —

Fixed income securities 52 52 — — 47 47 — —

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Total OPEB plan assets $ 59 $ 61

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Fair Level Level Level Fair Level Level Level

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Costs related to the 401(k) savings plans, which are partially based on the participants’ contributions and include allocated costs associated with Corporate Services employees for IPL and WPL, were as follows (in millions):

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Alliant Energy IPL WPL

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401(k) costs $ 31 $ 30 $ 28 $ 14 $ 14 $ 13 $ 15 $ 14 $ 13

Restructuring and Voluntary Employee Separation Charges - In 2024, Alliant Energy announced restructuring activities, including offering certain employees a voluntary separation package.

Approximately 5 % of total Alliant Energy employees accepted the package, and as a result of the restructuring activities, Alliant Energy, IPL and WPL recorded pre-tax charges of $ 29 million, $ 14 million and $ 13 million, respectively, in 2024.

These charges were primarily recorded in “Other operation and maintenance” expenses in the income statements.

NOTE 12 (b) Equity-based Compensation Plans - In 2020, Alliant Energy’s shareowners approved the 2020 OIP, which permits the grant of shares of Alliant Energy common stock, restricted stock, restricted stock units, performance shares, performance units, and other stock-based or cash-based awards to key employees.

At December 31, 2023, performance shares and restricted stock units (performance- and time-vesting) were outstanding under the 2020 OIP, and 8 million shares of Alliant Energy common stock remained available for grants under the 2020 OIP.

At December 31, 2024, performance shares and restricted stock units were outstanding under the 2020 OIP, and 7 million shares of Alliant Energy common stock remained available for grants under the 2020 OIP.

Alliant Energy satisfies share payouts related to equity awards through the issuance of new shares of its common stock.

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As of December 31, 2024, 564,743 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

Performance Shares - Equity Awards - Payouts of performance shares are contingent upon achievement over a three-year period of specified performance criteria, which currently is total shareowner return relative to an investor-owned utility peer group.

Performance Shares (Total Shareowner Return Metric) - Payouts of certain performance shares are contingent upon achievement over a three-year period of specified performance criteria, which currently is total shareowner return relative to an investor-owned utility peer group.

Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards.

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Nonvested awards, December 31 289,399 51.31 233,954 52.60 190,273 54.13

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Restricted Stock Units - Equity Awards - Payouts of restricted stock units are based on the expiration of a three-year time-vesting period.

Restricted Stock Units - Payouts of restricted stock units are based on the expiration of a three-year time-vesting period.

Restricted stock unit grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards.

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A summary of the restricted stock units activity was as follows:

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2024 2023 2022

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Date Fair Value

Nonvested units, January 1 198,275 $ 54.53 217,819 $ 50.54 146,549 $ 51.54

Nonvested awards, January 1 234,259 $ 52.58 198,275 $ 54.53 217,819 $ 50.54

Granted 129,854 48.69 106,124 52.77 77,122 56.88

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Forfeited ( 3,524 ) 48.40 ( 14,795 ) 54.53 ( 13,896 ) 55.53

Nonvested units, December 31 234,259 52.58 198,275 54.53 217,819 50.54

Performance Restricted Stock Units - Equity Awards - Payouts of performance restricted stock units are based upon achievement of certain performance targets during a three-year performance period, which currently includes specified growth of consolidated net income from continuing operations, as well as a diversity metric for the 2022 and 2023 grants.

The actual number of units that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200 % of the target number of units under each award type.

If minimum performance targets are not met during the performance period, these units are forfeited.

Performance restricted stock units are to be paid out in shares and are accounted for as equity awards.

The fair value of each performance restricted stock unit is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award.

Nonvested awards, December 31 289,148 51.85 234,259 52.58 198,275 54.53

Performance Shares (Net Income and Workforce Composition Metrics) (formerly granted as Performance Restricted Stock Units) - Payouts of certain performance shares are contingent upon achievement over a three-year period of specific performance criteria, which currently is specified growth of cumulative consolidated net income from continuing operations, as well as a workforce composition metric.

Performance shares grants are to be paid out in shares of Alliant Energy common stock and are accounted for as equity awards.

The fair value of each of these performance shares is based on the closing market price of one share of Alliant Energy common stock on the grant date of the award.

The actual number of these performance shares that will be paid out upon vesting is dependent upon actual performance and may range from zero to 200 % of the target number of shares under each award type.

If minimum performance targets are not met during the performance period, these performance shares are forfeited.

Compensation expense is recorded ratably over the performance period based on a probability assessment of payouts for the awards at each reporting period.

A summary of the performance restricted stock units activity, with amounts representing the target number of units, was as follows:

A summary of the performance shares activity, with amounts representing the target number of awards, was as follows:

2024 2023 2022

Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value Units Weighted Average Grant Date Fair Value

Nonvested units, January 1 199,874 $ 54.74 196,429 $ 50.74 197,463 $ 47.31

Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value Shares Weighted Average Grant Date Fair Value

Nonvested awards, January 1 257,639 $ 52.76 199,874 $ 54.74 196,429 $ 50.74

Granted 146,143 48.55 124,217 52.71 84,670 57.01

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Forfeited ( 5,230 ) 48.40 ( 13,021 ) 55.47 ( 10,124 ) 55.92

Nonvested units, December 31 257,639 52.76 199,874 54.74 196,429 50.74

Nonvested awards, December 31 330,700 51.81 257,639 52.76 199,874 54.74

NOTE 12 (c) Deferred Compensation Plan - Alliant Energy maintains a DCP under which certain key employees may defer up to 100 % of base salary and short-term cash incentive compensation and members of its Board of Directors may elect to defer all or part of their retainer and committee fees.

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Key employees and Board of Directors members may elect to have their deferrals credited to a company stock account, an interest account, equity accounts or mutual fund accounts based on certain benchmark funds.

Company Stock Account - The DCP does not permit diversification of deferrals credited to the company stock account and all distributions from participants’ company stock accounts are made in the form of shares of Alliant Energy common stock.

Company Stock Account - The DCP does not permit reallocation of deferrals credited to the company stock account and all distributions from participants’ company stock accounts are made in the form of shares of Alliant Energy common stock.

The deferred compensation obligations for participants’ company stock accounts are recorded in “Additional paid-in capital” and the shares of Alliant Energy common stock held in a rabbi trust to satisfy this obligation are recorded in “Shares in deferred compensation trust” on Alliant Energy’s balance sheets.

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ASSET RETIREMENT OBLIGATIONS

Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, wind farms, active ash landfills, ash ponds, solar generation, above ground storage tanks and batteries.

Recognized AROs relate to legal obligations for the removal, closure, dismantlement and management of several assets including, but not limited to, active and inactive ash landfills, ash ponds, wind farms, groundwater, solar facilities, above ground storage tanks and batteries.

Recognized AROs also include legal obligations for the management and final disposition of asbestos and polychlorinated biphenyls.

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Liabilities settled ( 8 ) ( 51 ) ( 6 ) ( 44 ) ( 2 ) ( 7 )

Liabilities incurred 16 6 1 — 15 6

Liabilities incurred (a) 409 16 201 1 208 15

Accretion expense 19 8 8 5 11 3

Balance, December 31 $ 663 $ 246 $ 350 $ 148 $ 313 $ 98

(a) In 2024, substantially due to the enactment of the revised CCR Rule, which significantly expands the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities, Alliant Energy, IPL and WPL initially recorded additional AROs, additional ARO regulatory assets for EGUs no longer in operation, additional property, plant and equipment for EGUs still in operation, and a pre-tax non-cash charge of $ 20 million recorded to “Other operation and maintenance” in Alliant Energy’s and IPL’s income statements for the portion allocated to IPL’s steam business for IPL’s Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews.

The amounts initially recorded in 2024 are expected to be adjusted in the future as additional information is obtained for the specific site closure plans, including the determination of whether or not individual sites are considered legal obligations and the acceptance and approval of compliance approaches, which could change management assumptions and result in a material change to the recorded amounts.

DERIVATIVE INSTRUMENTS

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Notional Amounts - As of December 31, 2024, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

Electricity FTRs Natural Gas

MWhs Years MWhs Years Dths Years

Electricity FTRs Natural Gas Diesel Fuel

MWhs Years MWhs Years Dths Years Gallons Years

Alliant Energy 1,422 2025-2026 10,232 2025 147,894 2025-2032 2,520 2025

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Non-current derivative liabilities 32 47 2 8 30 39

In 2023, Alliant Energy’s, IPL’s and WPL’s derivative assets decreased primarily due to settlements of natural gas and electricity contracts, and lower natural gas prices.

Alliant Energy’s, IPL’s and WPL’s non-current derivative liabilities increased primarily due to lower natural gas prices.

Alliant Energy’s and IPL’s current derivative liabilities decreased primarily due to settlements of natural gas contracts.

In 2024, Alliant Energy’s, IPL’s and WPL’s derivative liabilities decreased primarily due to settlements of natural gas contracts and higher natural gas prices.

Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets.

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Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings.

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In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid.

At December 31, 2023 and 2022, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.

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At December 31, 2024 and 2023, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different th an amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.

Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets.

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The related interest rate derivative was valued based on quoted prices that utilize current market interest rate forecasts.

As of December 31, 2023, $ 1 million of non-current interest rate derivative assets was recorded in “Deferred charges and other” on Alliant Energy’s balance sheet.

As of both December 31, 2024 and 2023, $ 1 million of non-current interest rate derivative assets was recorded in “Deferred charges and other” on Alliant Energy’s balance sheets.

This interest rate derivative was designated as a cash flow hedge, with changes in fair value recorded as other comprehensive income/loss.

As of December 31, 2023, accumulated other comprehensive income included $ 1 million of income related to the interest rate swap.

In 2023, $ 3 million of reductions to interest expense were recorded in Alliant Energy’s income statement related to the interest rate swap.

As of both December 31, 2024 and 2023, accumulated other comprehensive income included $ 1 million of income related to the interest rate swap.

In 2024 and 2023, $ 4 million and $ 3 million, respectively, of reductions to interest expense were recorded in Alliant Energy’s income statement related to the interest rate swap.

FAIR VALUE MEASUREMENTS

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Swap, option and physical forward commodity contracts were predominately at liquid trading points.

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FTRs were valued using auction prices and were categorized as Level 3.

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Refer to Note 5(b) for additional information regarding deferred proceeds.

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Long-term debt (including current maturities) - The fair value of long-term debt instruments was based on a discounted cash flow methodology using observable data from comparably traded securities with similar credit profiles, and was substantially classified as Level 2.

Refer to Note 8 (b) for additional information regarding long-term debt.

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments.

Carrying amounts and the related estimated fair values of other financial instruments at December 31 were as follows (in millions):

Carrying amounts and related estimated fair values of other financial instruments at December 31 were as follows (in millions):

Alliant Energy 2024 2023

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Deferred proceeds 163 — — 163 163 216 — — 216 216

Liabilities and equity:

Commodity derivatives 58 — 56 2 58 98 — 93 5 98

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Deferred proceeds 163 — — 163 163 216 — — 216 216

Liabilities and equity:

Commodity derivatives 13 — 11 2 13 30 — 25 5 30

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Amount 1 2 3 Total Amount 1 2 3 Total

Money market fund investments $ 43 $ 43 $ — $ — $ 43 $ — $ — $ — $ — $ —

Commodity derivatives 27 — 22 5 27 34 — 29 5 34

Liabilities and equity:

Commodity derivatives 45 — 45 — 45 68 — 68 — 68

Long-term debt 3,370 — 3,170 — 3,170 3,070 — 2,933 — 2,933

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Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

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The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at December 31 ($ 3 ) $ 3 $ — $ —

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IPL Commodity Contract Derivative

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Beginning balance, January 1 $ 5 $ 3

Total net gains (losses) included in changes in net assets (realized/unrealized) 6 ( 6 )

Total net gains included in changes in net assets (realized/unrealized) 1 6

Purchases 14 11

Sales ( 1 ) —

Settlements (a) ( 15 ) ( 22 )

Settlements ( 14 ) ( 15 )

Ending balance, December 31 $ 5 $ 5

The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at December 31 $ 1 $ 6

(a) Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) at December 31 as follows (in millions):

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets at December 31 as follows (in millions):

Alliant Energy IPL WPL

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COMMITMENTS AND CONTINGENCIES

NOTE 17 (a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including IPL’s and WPL’s expansion of solar generation, WPL’s expansion of battery storage, and IPL’s repowering of the existing Franklin County wind farm.

NOTE 16 (a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including IPL’s and WPL’s expansion of energy storage, and improvements at WPL’s natural gas-fired Neenah Energy Facility and Sheboygan Falls Energy Facility.

At December 31, 2024, Alliant Energy’s, IPL’s, and WPL’s minimum future commitments in 2025 for these projects were $ 448 million, $ 294 million, and $ 153 million, respectively.

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NOTE 16 (b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers.

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$ 212 $ 125 $ 97 $ 71 $ 51 $ 41 $ 597

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WPL 2025 2026 2027 2028 2029 Thereafter Total

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NOTE 16 (d) Guarantees and Indemnifications -

Whiting Petroleum - Whiting Petroleum is an independent oil and gas company.

In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum.

Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry.

Whiting Petroleum Corporation (Whiting Petroleum) - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum, an independent oil and gas company.

Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, has guaranteed the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry.

The guarantees do not include a maximum limit.

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The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations.

Whiting Petroleum previously completed bankruptcy proceedings and business combinations, which substantially reduce the likelihood that Alliant Energy will be obligated to make any payments under these guarantees.

As of December 31, 2024, the currently known partnership obligations for the abandonment obligations are estimated at $ 54 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees.

Alliant Energy estimates its expected loss to be a portion of the $ 49 million of known partnership abandonment obligations of the Whiting Petroleum affiliate and the other partners.

Alliant Energy is not aware of any material liabilities related to these guarantees that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of December 31, 2023 and 2022.

Whiting Petroleum completed a business combination with Oasis Petroleum Inc.

The combined operations are now known as Chord Energy Corporation.

The business combination is not expected to affect the scope of the Whiting Petroleum affiliate’s obligations to Alliant Energy or Alliant Energy’s related guarantees.

Alliant Energy is not currently aware of, nor does it currently expect to incur in the future, any material liabilities related to these guarantees and therefore has not recognized any material liabilities related to these guarantees as of December 31, 2024 and 2023.

Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma.

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Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of December 31, 2024 and 2023.

Transfers of Renewable Tax Credits - In 2023, IPL and WPL entered into agreements to transfer renewable tax credits from certain wind, solar and battery storage facilities to other corporate taxpayers in exchange for cash.

IPL and WPL provided indemnifications associated with $ 76 million and $ 22 million, respectively, of proceeds for renewable tax credits transferred to other corporate taxpayers in 2023 in the event of an adverse interpretation of tax law, including whether the related tax credits meet the qualification requirements.

Transfers of Renewable Tax Credits - In 2023 and 2024, IPL and WPL entered into agreements to transfer renewable tax credits from certain wind, solar and energy storage facilities to other corporate taxpayers in exchange for cash.

As of December 31, 2024, IPL and WPL provided indemnifications associated with $ 193 million and $ 121 million, respectively, of proceeds for renewable tax credits transferred to other corporate taxpayers in the event of an adverse interpretation of tax law,

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including whether the related tax credits meet the qualification requirements.

Alliant Energy, IPL and WPL believe the likelihood of having to make any material cash payments under these indemnifications is remote.

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IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment.

At December 31, 2023, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the

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MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

At December 31, 2024, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

Alliant Energy IPL WPL

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The geographic concentration of IPL’s and WPL’s customers did not contribute significantly to overall credit risk exposure.

In addition, as a result of a diverse customer base, IPL and WPL did not have any significant credit risk concentration for receivables arising from the sale of electricity or gas services.

Alliant Energy, IPL and WPL are subject to credit risk related to the ability of counterparties to meet their contractual payment obligations or the potential non-performance of counterparties to deliver contracted commodities and other goods or services at the contracted price.

In addition, as a result of a large customer base, IPL and WPL did not have any significant credit risk concentration for receivables arising from the sale of electricity or gas services.

Alliant Energy, IPL and WPL are subject to credit risk related to the ability of counterparties to meet their contractual payment obligations, including reimbursement of transmission costs from large load growth customers, or the potential non-performance of counterparties to deliver contracted commodities and other goods or services at the contracted price.

Credit policies are maintained to mitigate credit risk.

These credit policies include evaluation of the financial condition of certain counterparties, use of credit risk-related contingent provisions in certain agreements that require credit support from counterparties not meeting specific criteria, diversification of counterparties to reduce concentrations of credit risk and the use of standardized agreements that facilitate the netting of cash flows associated with certain counterparties.

Based on these credit policies and counterparty diversification, as well as utility cost recovery mechanisms, it is unlikely that counterparty non-performance would have a material effect on financial condition or results of operations.

These credit policies include evaluation of the financial condition of certain counterparties, use of credit risk-related contingent provisions in certain agreements that require credit support from counterparties not meeting specific criteria, different counterparties to reduce concentrations of credit risk and the use of standardized agreements that facilitate the netting of cash flows associated with certain counterparties.

Based on these credit policies and different counterparties, as well as utility cost recovery mechanisms, it is unlikely that counterparty non-performance would have a material effect on financial condition or results of operations.

However, there is no assurance that these items will protect against all losses from counterparty non-performance.

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In 2022, the U.S.

Court of Appeals for the District of Columbia vacated FERC’s prior orders that established the base return on equity authorized for the MISO transmission owners and remanded the cases to FERC for further proceedings, which may result in additional changes to the base return on equity authorized for the MISO transmission owners.

As a result of the 2022 court decision, Alliant Energy recorded a $ 6 million reduction in “Equity income from unconsolidated investments” in its income statement in 2022 to reflect the anticipated reduction in the base return on equity authorized for the MISO transmission owners.

Any further changes in FERC’s decisions may have an impact on Alliant Energy’s share of ATC’s future earnings and customer costs.

NOTE 17 (h) Collective Bargaining Agreements - At December 31, 2023, employees covered by collective bargaining agreements represented 53 %, 69 % and 83 % of total employees of Alliant Energy, IPL and WPL, respectively.

In August 2024, IPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 204 (Cedar Rapids) expires, representing 18 % and 53 % of total employees of Alliant Energy and IPL, respectively.

Court of Appeals for the District of Columbia vacated FERC’s prior orders that established the base return on equity authorized

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for the MISO transmission owners and remanded the cases to FERC for further proceedings.

As a result of the 2022 court decision, Alliant Energy recorded a $ 6 million reduction in “Equity income from unconsolidated investments” in its income statement in 2022 to reflect the then-anticipated reduction in the base return on equity authorized for the MISO transmission owners.

In October 2024, FERC issued an order reducing the base return on equity authorized for MISO transmission owners to 9.98 %, and as a result, the MISO transmission owners will provide refunds based on the 9.98 % base return on equity, with interest, for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016, which did not result in any material impacts on Alliant Energy’s results of operations or financial condition in 2024.

Any further changes in FERC’s decisions may have an impact on Alliant Energy’s share of ATC’s future earnings and customer costs;

however, Alliant Energy is currently unable to predict with certainty the future outcome or impact of any further changes.

SEGMENTS OF BUSINESS

Alliant Energy - Alliant Energy’s principal businesses as of December 31, 2023 are:

• Utility - includes the operations of IPL and WPL, which primarily serve retail customers in Iowa and Wisconsin.

The utility business has three reportable segments:

a) utility electric operations;

b) utility gas operations;

and c) utility other, which includes steam operations and the unallocated portions of the utility business.

Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total Utility.”

• ATC Holdings, Non-utility, Parent and Other - includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments.

Alliant Energy - Alliant Energy’s reportable segments as of December 31, 2024 are:

• IPL - is a utility primarily serving electric and natural gas customers in Iowa, and is its own reportable segment as shown in the tables below.

• WPL - is a utility serving electric and natural gas customers in Wisconsin, and is its own reportable segment as shown in the tables below.

Other, which is not a reportable segment of Alliant Energy, includes the operations of AEF and its subsidiaries, Corporate Services, the Alliant Energy parent company, and any Alliant Energy parent company consolidating adjustments.

AEF is comprised of Alliant Energy’s interest in ATC Holdings, Travero, a non-utility wind farm, corporate venture investments, the Sheboygan Falls Energy Facility and other non-utility holdings.

The “Other” columns are included in the tables below to reconcile to consolidated amounts.

Prior to December 31, 2024, reportable segments for Alliant Energy’s, IPL’s, and WPL’s utility business were electric operations, gas operations, and other.

In the fourth quarter of 2024, Alliant Energy, IPL and WPL adopted the Financial Accounting Standards Board’s accounting standard for improvements to reportable segment disclosures.

Previously reported information for prior periods has been recast to conform with the current period presentation.

Alliant Energy’s chief operating decision maker (CODM) is its President and CEO, and IPL’s and WPL’s CODM is their CEO.

The CODM uses net income generated from IPL’s and WPL’s operations to assess segment performance, make operating decisions, and allocate resources.

Alliant Energy’s administrative support services are directly charged to the applicable segment where practicable.

In all other cases, administrative support services are allocated to the applicable segment based on services agreements.

Intersegment revenues were not material to Alliant Energy’s operations and there was no single customer whose revenues were 10% or more of Alliant Energy’s consolidated revenues.

All of Alliant Energy’s operations and assets are located in the U.S.

Certain financial information relating to Alliant Energy’s business segments, which represent the services provided to its customers, was as follows (in millions):

ATC Holdings,

Utility Non-utility, Alliant Energy

2023 Electric Gas Other Total Parent and Other Consolidated

Revenues $ 3,345 $ 540 $ 52 $ 3,937 $ 90 $ 4,027

Depreciation and amortization 602 60 6 668 8 676

Operating income 827 70 19 916 27 943

There was no single customer whose revenues were 10% or more of Alliant Energy’s, IPL’s and WPL’s respective consolidated revenues.

All of Alliant Energy’s, IPL’s and WPL’s operations and assets are located in the U.S.

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):

Total Alliant

Reportable Energy

2024 IPL WPL Segments Other Consolidated

Electric utility revenues $ 1,747 $ 1,625 $ 3,372 N/A $ 3,372

Gas utility revenues 250 215 465 N/A 465

Other revenues 49 5 54 $ 90 144

Total revenues 2,046 1,845 3,891 90 3,981

Electric production fuel and purchased power expense 269 359 628 N/A 628

Electric transmission service expense 417 196 613 N/A 613

Cost of gas sold expense 123 101 224 N/A 224

Asset valuation charge for IPL’s Lansing Generation Station 60 — 60 N/A 60

Other operation and maintenance expense 358 279 637 39 676

Other segment items:

Depreciation and amortization expense 404 357 761 11 772

Interest expense 177 165 342 107 449

Equity income from unconsolidated investments, net — ( 2 ) ( 2 ) ( 59 ) ( 61 )

Income taxes 2 2 4

Net income (loss) attributable to Alliant Energy common shareowners 711 ( 8 ) 703

Income tax expense (benefit) ( 129 ) 11 ( 118 ) 4 ( 114 )

Other (a) 5 34 39 5 44

Net income (loss) 362 345 707 ( 17 ) 690

Total assets 11,407 10,106 21,513 1,201 22,714

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Construction and acquisition expenditures 1,224 828 2,052 197 2,249

ATC Holdings,

Utility Non-utility, Alliant Energy

2022 Electric Gas Other Total Parent and Other Consolidated

Revenues $ 3,421 $ 642 $ 49 $ 4,112 $ 93 $ 4,205

Depreciation and amortization 601 56 7 664 7 671

Operating income 805 97 3 905 23 928

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Total Alliant

Reportable Energy

2023 (amounts may not foot due to rounding)

IPL WPL Segments Other Consolidated

Electric utility revenues $ 1,761 $ 1,584 $ 3,345 N/A $ 3,345

Gas utility revenues 300 240 540 N/A 540

Other revenues 49 3 52 $ 90 142

Total revenues 2,110 1,827 3,937 90 4,027

Electric production fuel and purchased power expense 282 455 737 N/A 736

Electric transmission service expense 420 163 583 N/A 583

Cost of gas sold expense 166 134 300 N/A 299

Other operation and maintenance expense 353 271 624 51 675

Other segment items:

Depreciation and amortization expense 388 280 668 8 676

Interest expense 155 149 304 90 394

Equity income from unconsolidated investments, net — ( 3 ) ( 3 ) ( 58 ) ( 61 )

Income taxes 16 6 22

Net income attributable to Alliant Energy common shareowners 675 11 686

Income tax expense (benefit) ( 58 ) 60 2 2 4

Other (a) 38 ( 27 ) 11 5 18

Net income (loss) 366 345 711 ( 8 ) 703

Total assets 10,489 9,634 20,123 1,114 21,237

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Construction and acquisition expenditures 712 1,019 1,731 123 1,854

ATC Holdings,

Utility Non-utility, Alliant Energy

2021 Electric Gas Other Total Parent and Other Consolidated

Revenues $ 3,081 $ 456 $ 49 $ 3,586 $ 83 $ 3,669

Depreciation and amortization 591 54 6 651 6 657

Operating income (loss) 716 63 ( 11 ) 768 27 795

Total Alliant

Reportable Energy

2022 IPL WPL Segments Other Consolidated

Electric utility revenues $ 1,859 $ 1,562 $ 3,421 N/A $ 3,421

Gas utility revenues 351 291 642 N/A 642

Other revenues 46 3 49 $ 93 142

Total revenues 2,256 1,856 4,112 93 4,205

Electric production fuel and purchased power expense 383 447 830 N/A 830

Electric transmission service expense 407 166 573 N/A 573

Cost of gas sold expense 206 183 389 N/A 389

Other operation and maintenance expense 369 278 647 57 704

Other segment items:

Depreciation and amortization expense 381 283 664 7 671

Interest expense 148 121 269 56 325

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Income tax expense (benefit) ( 50 ) 66 16 6 22

Net income attributable to Alliant Energy common shareowners 618 41 659

Total assets 14,924 1,487 1,103 17,514 1,039 18,553

Investments in equity method subsidiaries 17 — — 17 491 508

Construction and acquisition expenditures 980 90 — 1,070 99 1,169

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IPL - IPL is a utility primarily serving retail customers in Iowa and includes three reportable segments:

a) electric operations;

b) gas operations;

and c) other, which includes steam operations and the unallocated portions of the utility business.

Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to IPL’s operations and there was no single customer whose revenues were 10% or more of IPL’s consolidated revenues.

All of IPL’s operations and assets are located in the U.S.

Certain financial information relating to IPL’s business segments, which represent the services provided to its customers, was as follows (in millions):

2023 Electric Gas Other Total

Revenues $ 1,761 $ 300 $ 49 $ 2,110

Depreciation and amortization 348 34 6 388

Operating income 390 35 19 444

Interest expense 155

Income tax benefit ( 58 )

Net income available for common stock 366

Total assets 9,311 921 257 10,489

Construction and acquisition expenditures 671 41 — 712

2022 Electric Gas Other Total

Revenues $ 1,859 $ 351 $ 46 $ 2,256

Depreciation and amortization 342 32 7 381

Operating income 397 53 3 453

Interest expense 148

Income tax benefit ( 50 )

Net income available for common stock 360

Total assets 8,686 872 517 10,075

Construction and acquisition expenditures 336 36 — 372

2021 Electric Gas Other Total

Revenues $ 1,752 $ 265 $ 46 $ 2,063

Depreciation and amortization 338 31 6 375

Operating income (loss) 420 43 ( 3 ) 460

Interest expense 139

Income tax benefit ( 36 )

Net income available for common stock 350

Total assets 8,602 819 575 9,996

Construction and acquisition expenditures 342 42 — 384

WPL - WPL is a utility serving customers in Wisconsin and includes three reportable segments:

a) electric operations;

b) gas operations;

and c) other, which includes the unallocated portions of the utility business.

Various line items in the following tables are not allocated to the electric and gas segments for management reporting purposes, and therefore, are included only in “Total.” Intersegment revenues were not material to WPL’s operations and there was no single customer whose revenues were 10% or more of WPL’s consolidated revenues.

All of WPL’s operations and assets are located in the U.S.

Certain financial information relating to WPL’s business segments, which represent the services provided to its customers, was as follows (in millions):

2023 Electric Gas Other Total

Revenues $ 1,584 $ 240 $ 3 $ 1,827

Depreciation and amortization 254 26 — 280

Operating income 437 35 — 472

Interest expense 149

Income taxes 60

Net income 345

Total assets 8,522 763 349 9,634

Construction and acquisition expenditures 970 49 — 1,019

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2022 Electric Gas Other Total

Revenues $ 1,562 $ 291 $ 3 $ 1,856

Depreciation and amortization 259 24 — 283

Operating income 408 44 — 452

Interest expense 121

Income taxes 66

Net income 315

Total assets 7,885 759 343 8,987

Construction and acquisition expenditures 982 38 — 1,020

2021 Electric Gas Other Total

Revenues $ 1,329 $ 191 $ 3 $ 1,523

Depreciation and amortization 253 23 — 276

Operating income (loss) 296 20 ( 8 ) 308

Interest expense 105

Income tax benefit ( 51 )

Other (a) 52 ( 2 ) 50 6 56

Net income 360 315 675 11 686

Total assets 10,075 8,987 19,062 1,101 20,163

Investments in equity method subsidiaries 5 15 20 522 542

Construction and acquisition expenditures 372 1,020 1,392 92 1,484

(a) Other segment items for each reportable segment include AFUDC, taxes other than income taxes, interest income, and other miscellaneous income and deductions.

RELATED PARTIES

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As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO.

Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO.

Corporate Services assigns such sales and purchases among IPL and WPL based on

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statements received from MISO.

The amounts billed for services provided, sales credited and purchases were as follows (in millions):

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CHANGES IN AND DISAGREEMENTS WITH ACCOUNTANTS ON ACCOUNTING AND FINANCIAL DISCLOSURE

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Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-K

Item 8. Financial Statements and Supplementary Data