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 diluted EPS attributable to Alliant Energy common shareowners for the three and nine months ended September 30 were as follows (dollars in millions, except per share amounts):

Alliant Energy’s Utilities and Corporate Services net income increased by $120 million for the three-month period, primarily due to the timing of income taxes, higher revenue requirements from IPL’s and WPL’s capital investments, higher allowance for funds used during construction and higher retail electric sales. These items were partially offset by higher other operation and maintenance, financing and depreciation expenses.

Alliant Energy’s Non-utility and Parent net income decreased by $6 million for the three-month period, primarily due to the timing of income taxes and higher financing expense, partially offset by higher equity earnings from corporate venture investments and a state income tax apportionment charge in 2025.

Alliant Energy’s Utilities and Corporate Services net income increased by $68 million for the nine-month period, primarily due to higher revenue requirements from IPL’s and WPL’s capital investments, the timing of income taxes, higher allowance for funds used during construction and higher retail electric sales. These items were partially offset by higher other operation and maintenance, financing and depreciation expenses.

Alliant Energy’s Non-utility and Parent net income increased by $51 million for the nine-month period, primarily due to higher equity earnings from corporate venture investments, a state income tax apportionment benefit in 2026 and a state income tax apportionment charge in 2025, partially offset by higher financing expense.

Net Income Variances -The following items contributed to increased (decreased) net income for the three and nine months ended September 30, 2026 compared to the same periods in 2025 (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 2% and increased 1% for the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025, primarily due to higher sales to commercial and industrial customers at WPL and changes in temperatures, which increased sales volumes for the three-month period and decreased sales volumes for the nine-month period, compared to the same periods in 2025. Alliant Energy’s retail gas sales volumes decreased 2% and decreased 5% for the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025, primarily due to changes in temperatures and lower sales to industrial customers at IPL.

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 -Alliant Energy’s and IPL’s wholesale sales volumes decreased for the three and nine months ended September 30, 2026, respectively, compared to the same periods in 2025, primarily due to the expiration of IPL’s wholesale power agreement with Southern Minnesota Energy Cooperative in 2025.

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, 2026 compared to the same periods in 2025 (in millions):

(a)In December 2025, the PSCW issued an order authorizing an annual base rate increase of $69 million for WPL’s retail electric customers, covering the 2026 forward-looking Test Period, which reflects revenue requirement impacts of increasing electric rate base, including wind refurbishment projects, energy storage, existing natural gas-fired EGU improvements and electric distribution investments and lower forecasted fuel-related expenses.

(b)Sales for resale bulk power and other revenues increased for the three and nine months ended September 30, 2026 compared to the same periods in 2025, 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.

Gas Utility Revenue Variances -The following items contributed to increased (decreased) gas utility revenues for the three and nine months ended September 30, 2026 compared to the same periods in 2025 (in millions):

(a)In December 2025, the PSCW issued an order authorizing an annual base rate increase of $7 million for WPL’s retail gas customers, covering the 2026 forward-looking Test Period, which reflects revenue requirement impacts of increasing gas rate base.

Electric Production Fuel and Purchased Power Expenses Variances -The following items contrib uted to (increased) decreased electric production fuel and purchased power expenses for the three and nine months ended September 30, 2026 compared to the same periods in 2025 (in millions):

(a)Purchased power expense decreased for the nine months ended September 30, 2026 compared to the same period in 2025, primarily due to lower prices for electricity purchased at IPL.

(b)Electric production fuel costs increased for the nine months ended September 30, 2026 compared to the same period in 2025, primarily due to higher natural gas prices and higher natural gas volumes at WPL due to higher dispatch of natural gas-fired EGUs, partially offset by lower coal volumes at WPL due to lower dispatch of coal-fired EGUs.

Electric Transmission Service Expense Variances -The following items contributed to (increased) decreased elec tric transmission service expense for the three and nine months ended September 30, 2026 compared to the same periods in 2025 (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, 2026 compared to the same periods in 2025 (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, 2026 compared to the same periods in 2025 (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-

•Common Stock - For the remainder of 2026, Alliant Energy currently expects to physically settle up to $650 million of outstanding forward sale agreements in aggregate under the 2025 and/or 2026 at-the-market offering programs (ATM programs). From 2027 through 2030, Alliant Energy currently expects to issue up to $2.7 billion of common stock in aggregate through the ATM programs, its Shareowner Direct Plan (approximately $25 million in common stock annually) and additional future equity offerings. Refer to Note 5 for further details of common stock issuances and settlements under the 2025 and 2026 ATM programs.

•Long-term Debt - For the remainder of 2026, IPL and WPL currently expect to issue up to $200 million and $300 million of long-term debt, respectively, and in 2027, up to $1.3 billion and $500 million of long-term debt, respectively. Future IPL and WPL long-term debt issuances may include funding through the DOE Loan Guarantee Program. Refer to Liquidity and Capital Resources for further details of the program. In 2027, AEF and/or Alliant Energy at the parent company level expect to issue up to $1 billion of long-term debt in aggregate. AEF and WPL have $375 million and $300 million, respectively, of long-term debt maturing in 2027.

•Common Stock Dividends - Alliant Energy announced a 5% increase in its targeted 2027 annual common stock dividend to $2.25 per share, which is equivalent to a quarterly rate of $0.5625 per share, beginning with the February 2027 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.

•Cash Flows from Operating Activities - Alliant Energy, IPL and WPL currently expect an increase in future cash flows from operating activities resulting from the transfer of future renewable tax credits to other corporate taxpayers. Refer to Note 8 for renewable tax credits transferred in October 2026. In addition, Alliant Energy, IPL and WPL currently expect an increase in future cash flows from operating activities resulting from higher retail electric sales in 2027 driven by large load growth customers. Alliant Energy and WPL also expect an increase in future cash flows from operating activities resulting from higher earnings on WPL’s increasing rate base.

•Higher Earnings on Increasing Rate Base - Alliant Energy and WPL currently expect electric and gas utility revenues to increase in 2027 compared to 2026, primarily due to impacts from increasing revenue requirements related to investments in the utility business. IPL currently expects an increase in its effective income tax rate in 2027 compared to 2026 due to higher income before income taxes, partially offset by greater utilization of investment tax credits. Investment tax credits resulting from IPL energy storage projects placed in service and/or expected to be placed in service in 2026 and 2027 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 2027 compared to 2026 driven by large load growth customers, including data center customers and other economic development activities. Refer to “Growing Customer Demand” for further discussion.

•Depreciation and Amortization Expense - Alliant Energy, IPL and WPL currently expect an increase in depreciation and amortization expense in 2027 compared to 2026 due to capital projects placed in service in 2026 and 2027.

•Interest Expense - Alliant Energy, IPL and WPL currently expect an increase in interest expense in 2027 compared to 2026 due to financings completed in 2026 and planned in 2027.

•Equity Income from Unconsolidated Investments- Alliant Energy’s equity earnings from certain corporate venture fund investments have increased during 2026 due to increased valuations of certain underlying investments within the venture funds. Refer to Note 4 for further details.

•Allowance for Funds Used During Construction - Alliant Energy, IPL and WPL currently expect an increase in allowance for funds used during construction in 2027 compared to 2026 largely due to changes in construction work in progress balances related to construction activity on capital projects.