ALLIANT ENERGY CORP

RESULTS OF OPERATIONS

Financial Results Overview -The table below includes diluted EPS for Utilities and Corporate Services, ATC Holdings, and Non-utility and Parent, which are non-GAAP financial measures. Alliant Energy believes these non-GAAP financial measures are useful to investors because they facilitate an understanding of performance and trends, and provide additional information about Alliant Energy’s operations on a basis consistent with the measures that management uses to manage its operations and evaluate its performance. Alliant Energy’s net income and EPS attributable to Alliant Energy common shareowners for the three months ended September 30 were as follows (dollars in millions, except per share amounts):

Alliant Energy’s Utilities and Corporate Services net income decreased by $16 million for the three-month period, primarily due to higher other operation and maintenance expenses, the timing of income tax expense, higher depreciation and financing expenses. These items were partially offset by higher revenue requirements from IPL’s and WPL’s capital investments.

Alliant Energy’s Non-utility and Parent net income increased $1 million for the three-month period, primarily due to the timing of income taxes, partially offset by a state income tax apportionment charge.

Net Income Variances -The following items contributed to increased (decreased) net income for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

Electric and Gas Revenues and Sales Summary -Electric and gas revenues (in millions), and MWh and Dth sales (in thousands), for the three and nine months ended September 30 were as follows:

Sales Trends and Temperatures - Alliant Energy’s retail electric sales volumes increased 4% and 2% for the three and nine months ended September 30, 2025, respectively, compared to the same periods in 2024, primarily due to changes in temperatures and higher sales to industrial customers. Alliant Energy’s retail gas sales volumes increased 14% for the nine months ended September 30, 2025, compared to the same period in 2024, primarily due to changes in temperatures.

Estimated increases (decreases) to operating income from the impacts of temperatures for the three and nine months ended September 30 were as follows (in millions):

Electric Sales for Resale - Bulk Power and Other -Bulk power and other volume changes were due to changes in sales in the wholesale energy markets operated by MISO. These changes are impacted by several factors, including the availability and dispatch of Alliant Energy’s EGUs and electricity demand within these wholesale energy markets. Changes in bulk power and other revenues were largely offset by changes in fuel-related costs, and therefore did not have a significant impact on operating income.

Gas Transportation/Other -Gas transportation/other sales volume changes were largely due to changes in the gas volumes supplied to Alliant Energy’s natural gas-fired EGUs caused by the availability and dispatch of such EGUs.

Electric Utility Revenue Variances -The following items contributed to increased (decreased) electric utility revenues for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

(a)In September 2024, the IUC issued an order authorizing an annual base rate increase 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, for the October 2024 through September 2025 forward-looking Test Period. Rate changes were effective October 1, 2024, which reflect revenue requirement impacts of increasing electric rate base including investments in solar generation, updated depreciation rates, and certain incremental costs incurred resulting from the 2020 derecho windstorm. In addition, effective October 1, 2024, IPL’s renewable energy rider was discontinued, and certain production tax credits are credited to IPL’s retail electric customers through IPL’s fuel-related cost recovery mechanism. Credits on IPL’s customers’ bills have been and are expected to be offset by a reduction in income tax expense.

(b)In December 2023, the PSCW issued an order authorizing an annual base rate increase of $60 million for WPL’s retail electric customers, covering the 2025 forward-looking Test Period, which reflects revenue requirement impacts of increasing electric rate base including investments in solar generation and energy storage.

(c)Sales for resale bulk power and other revenues increased primarily due to higher prices for electricity and capacity sold by IPL and WPL to MISO wholesale energy markets. These changes were largely offset by changes in fuel-related costs.

(d)WPL’s cost recovery mechanism for retail fuel-related expenses supports deferrals of amounts that fall outside an approved fuel monitoring range of forecasted fuel-related expenses determined by the PSCW each year. The difference between revenue collected and actual fuel-related expenses incurred within the fuel monitoring range increases or decreases Alliant Energy’s and WPL’s electric utility revenues. WPL estimates the increase (decrease) to electric utility revenues from amounts within the fuel monitoring range were approximately $1 million and $3 million for the three and nine months ended September 30, 2025, respectively, compared to $0 and ($4) million for the three and nine months ended September 30, 2024, respectively.

Gas Utility Revenue Variances -The following items contributed to increased (decreased) gas utility revenues for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

(a)In September 2024, the IUC issued an order authorizing an annual base rate increase of $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, which reflect revenue requirement impacts of increasing gas rate base.

Electric Production Fuel and Purchased Power Expenses Variances -The following items contributed to (increased) decreased electric production fuel and purchased power expenses for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

(a)Electric production fuel costs increased for the three and nine months ended September 30, 2025 compared to the same periods in 2024, primarily due to higher coal volumes due to higher dispatch of coal-fired EGUs and higher natural gas prices, partially offset by lower natural gas volumes due to lower dispatch of natural gas-fired EGUs.

(b)Purchased power expense increased for the three and nine months ended September 30, 2025 compared to the same periods in 2024, primarily due to higher prices for electricity purchased at WPL.

Electric Transmission Service Expense Variances -The following items contributed to (increased) decreased electric transmission service expense for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

Cost of Gas Sold Expense Variances -The following items contributed to (increased) decreased cost of gas sold expense for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

Other Operation and Maintenance Expenses Variances -The following items contributed to (increased) decreased other operation and maintenance expenses for the three and nine months ended September 30, 2025 compared to the same periods in 2024 (in millions):

Other Future Considerations - In addition to items discussed in this report, the following key items could impact Alliant Energy’s, IPL’s and WPL’s future financial condition or results of operations:

•Financing Plans- Alliant Energy currently expects to issue up to $2.4 billion of common stock in aggregate from 2026 through 2029 through the distribution agreement that was executed in May 2025, its Shareholder Direct Plan (up to $25 million in common stock annually) and additional future equity offerings. For the remainder of 2025, WPL currently expects to issue up to $300 million of long-term debt. In 2026, IPL and WPL currently expect to issue up to $500 million and $300 million, respectively, of long-term debt, and AEF and/or Alliant Energy at the parent company level expect to issue up to $300 million of long-term debt in aggregate. AEF and Alliant Energy at the parent company level have $500 million and $575 million, respectively, of long-term debt maturing in 2026.

•Common Stock Dividends - Alliant Energy announced a 5% increase in its targeted 2026 annual common stock dividend to $2.14 per share, which is equivalent to a quarterly rate of $0.535 per share, beginning with the February 2026 dividend payment. The timing and amount of future dividends is subject to approval of quarterly dividend declarations from Alliant Energy’s Board of Directors, and is dependent upon earnings expectations, capital requirements, and general financial business conditions, among other factors.

•Higher Earnings on Increasing Rate Base - Alliant Energy and WPL currently expect increases in electric utility and gas utility revenues in 2026 compared to 2025 due to impacts from increasing revenue requirements related to investments in the utility business (refer to “Rate Matters” for further discussion). Additionally, Alliant Energy and IPL currently expect electric utility revenues to increase in 2026 compared to 2025 due to the expiration of tax benefit rider credits in 2025. Furthermore, Alliant Energy, IPL and WPL currently expect a decrease in the effective income tax rate in 2026 compared to 2025 due to additional renewable tax credits from renewable generation and energy storage projects placed in service and/or expected to be placed in service in 2025 and 2026. 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. Investment tax credits resulting from IPL energy storage projects placed in service and/or expected to be placed in service in 2025 and 2026 may be utilized to offset any revenue deficiency on an annual basis up to the earnings sharing mechanism threshold included in IPL’s retail electric rate review settlement agreement.

•Sales Trends - Alliant Energy, IPL and WPL currently expect an increase in retail electric sales in 2026 compared to 2025 driven by expected load growth from new customers who currently expect to build data centers in IPL’s and WPL’s service territories. Refer to “Growing Customer Demand” for further discussion.

•Other Operation and Maintenance Expenses - Alliant Energy, IPL and WPL currently expect an increase in other operation and maintenance expenses in 2026 compared to 2025 largely due to higher generation maintenance and energy delivery expenses.

•Depreciation and Amortization Expense - Alliant Energy, IPL and WPL currently expect an increase in depreciation and amortization expense in 2026 compared to 2025 due to capital projects placed in service in 2025 and 2026.

•Interest Expense - Alliant Energy, IPL and WPL currently expect an increase in interest expense in 2026 compared to 2025 due to financings completed in 2025 and planned in 2026 as discussed above.

•Allowance for Funds Used During Construction - Alliant Energy, IPL and WPL currently expect an increase in allowance for funds used during construction in 2026 compared to 2025 largely due to changes in construction work in progress balances related to construction activity on capital projects.

LIQUIDITY AND CAPITAL RESOURCES

The liquidity and capital resources summary included in the 2024 Form 10-K has not changed materially, except as described below.

Liquidity Position -At September 30, 2025, Alliant Energy had $503 million of cash and cash equivalents, $250 million of short-term investments, $1,108 million ($550 million at the parent company, $350 million at IPL and $208 million at WPL) of available capacity under the single revolving credit facility and $4 million of available capacity at IPL under its sales of accounts receivable program.

Capital Structure -Financial capital structures at September 30, 2025 were as follows (Long-term Debt (including current maturities) (LD); Short-term Debt (SD); Common Equity (CE)):

(a)The long-term debt component of Alliant Energy’s financial capital structure includes junior subordinated notes classified as “Long-term debt, net” on Alliant Energy’s balance sheet (refer to Note 7 for additional information). 50% of the carrying amount of junior subordinated notes is excluded from the debt component of Alliant Energy’s debt-to-capital ratio used by the majority of rating agencies. Alliant Energy’s financial capital structure adjusted for the reclassification of 50% of the carrying amount of junior subordinated notes from long-term debt to common equity at September 30, 2025 was as follows: LD: 59%, CE: 40% and SD: 1%. The non-GAAP adjusted presentation reflecting this treatment is useful and relevant to investors in understanding how management and the rating agencies evaluate Alliant Energy’s capital structure.

Cash Flows -Selected information from the cash flows statements was as follows (in millions):

Operating Activities -The following items contributed to increased (decreased) operating activity cash flows for the nine months ended September 30, 2025 compared to the same period in 2024 (in millions):

(a)Refer to the cash flows statements for details of renewable tax credits transferred to other corporate taxpayers during the nine months ended September 30, 2025 and 2024.

Investing Activities - The following items contributed to increased (decreased) investing activity cash flows for the nine months ended September 30, 2025 compared to the same period in 2024 (in millions):

(a)Largely due to higher expenditures for IPL’s energy storage and gas generation, partially offset by lower expenditures for IPL’s and WPL’s solar generation and WPL’s energy storage.