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 June 30 were as follows (dollars in millions, except per share amounts):

Alliant Energy’s Utilities and Corporate Services net income increased by $105 million for the three-month period, primarily due to higher revenue requirements from IPL’s and WPL’s capital investments, an asset valuation charge in 2024 for IPL’s retired Lansing Generating Station, an ARO charge in 2024 allocated to the steam business at IPL due to the revised Coal Combustion Residuals Rule, and estimated temperature impacts on retail electric and gas sales. These items were partially offset by higher depreciation and financing expenses.

Alliant Energy’s Non-utility and Parent net income decreased $19 million for the three-month period, primarily due to lower equity income from corporate venture investments, higher financing expense and the timing of income taxes.

Net Income Variances -The following items contributed to increased (decreased) net income for the three and six months ended June 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 six months ended June 30 were as follows:

Sales Trends and Temperatures - Alliant Energy’s retail electric sales volumes were unchanged and increased 1% for the three and six months ended June 30, 2025, respectively, compared to the same periods in 2024, primarily due to changes in temperatures. Alliant Energy’s retail gas sales volumes increased 7% and 16% for the three and six months ended June 30, 2025, respectively, compared to the same periods in 2024, primarily due to changes in temperatures.

Estimated increases (decreases) to operating income from the impacts of temperatures for the three and six months ended June 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 six months ended June 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)Alliant Energy’s and WPL’s sales for resale bulk power and other revenues increased primarily due to higher prices for electricity and capacity sold by 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 $6 million and $2 million for the three and six months ended June 30, 2025, respectively, compared to ($5) million and ($4) million for the three and six months ended June 30, 2024, respectively.

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

(a)Electric production fuel costs increased for the three and six months ended June 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 six months ended June 30, 2025 compared to the same period 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 six months ended June 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 six months ended June 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 six months ended June 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 $1.3 billion of common stock in aggregate from 2026 through 2028 through the distribution agreement that was executed in May 2025, and up to $25 million of common stock annually through its Shareowner Direct Plan in 2025 through 2028. For the remainder of 2025, IPL and WPL currently expect to issue up to $400 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 $725 million of long-term debt in aggregate. IPL has $250 million of long-term debt maturing in August 2025.

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 June 30, 2025, Alliant Energy had $329 million of cash and cash equivalents, $1,008 million ($550 million at the parent company, $350 million at IPL and $108 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 June 30, 2025 were as follows (Long-term Debt (including current maturities) (LD); Short-term Debt (SD); Common Equity (CE)):

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 six months ended June 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 six months ended June 30, 2025 and 2024.

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

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