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Benefit Plans | 3 Months Ended
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Mar. 31, 2024
Benefit Plans | BENEFIT PLANS NOTE 10(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are 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.
| Defined Benefit Pension Plans |  | OPEB Plans
Alliant Energy | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Service cost | $1 |  | $1 |  |  |  |  |  | $— |  | $1 |  |  |  |
Interest cost | 11 |  | 11 |  |  |  |  |  | 2 |  | 2 |  |  |  |
Expected return on plan assets | (13) |  | (13) |  |  |  |  |  | (1) |  | (1) |  |  |  |
Amortization of actuarial loss | 6 |  | 7 |  |  |  |  |  | — |  | — |  |  |  |
| $5 |  | $6 |  |  |  |  |  | $1 |  | $2 |  |  |  |
| Defined Benefit Pension Plans |  | OPEB Plans
IPL | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Service cost | $1 |  | $1 |  |  |  |  |  | $— |  | $— |  |  |  |
Interest cost | 5 |  | 5 |  |  |  |  |  | 1 |  | 1 |  |  |  |
Expected return on plan assets | (7) |  | (7) |  |  |  |  |  | (1) |  | (1) |  |  |  |
Amortization of actuarial loss | 2 |  | 3 |  |  |  |  |  | — |  | — |  |  |  |
| $1 |  | $2 |  |  |  |  |  | $— |  | $— |  |  |  |
| Defined Benefit Pension Plans |  | OPEB Plans
WPL | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Interest cost | $5 |  | $5 |  |  |  |  |  | $1 |  | $1 |  |  |  |
Expected return on plan assets | (6) |  | (5) |  |  |  |  |  | — |  | — |  |  |  |
Amortization of actuarial loss | 3 |  | 3 |  |  |  |  |  | — |  | — |  |  |  |
| $2 |  | $3 |  |  |  |  |  | $1 |  | $1 |  |  |  |
NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Compensation expense | $4 |  | $3 |  |  |  |  |  | $2 |  | $2 |  |  |  |  |  | $2 |  | $1 |  |  |  |
Income tax benefits | 1 |  | 1 |  |  |  |  |  | 1 |  | — |  |  |  |  |  | — |  | — |  |  |  |
As of March 31, 2024, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $22 million, $11 million and $10 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the three months ended March 31, 2024, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.
|  |  | Weighted Average
| Grants |  | Grant Date Fair Value
Performance shares (total shareowner return metric) | 123,098 |  | $46.04
Performance shares (net income and diversity metrics) (formerly granted as performance restricted stock units) | 140,683 |  | 48.40
Restricted stock units | 120,557 |  | 48.40
As of March 31, 2024, 242,680 shares were included in the calculation of diluted EPS related to the nonvested equity awards.
IPL [Member] |
Benefit Plans | BENEFIT PLANS NOTE 10(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are 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.
| Defined Benefit Pension Plans |  | OPEB Plans
Alliant Energy | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Service cost | $1 |  | $1 |  |  |  |  |  | $— |  | $1 |  |  |  |
Interest cost | 11 |  | 11 |  |  |  |  |  | 2 |  | 2 |  |  |  |
Expected return on plan assets | (13) |  | (13) |  |  |  |  |  | (1) |  | (1) |  |  |  |
Amortization of actuarial loss | 6 |  | 7 |  |  |  |  |  | — |  | — |  |  |  |
| $5 |  | $6 |  |  |  |  |  | $1 |  | $2 |  |  |  |
| Defined Benefit Pension Plans |  | OPEB Plans
IPL | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Service cost | $1 |  | $1 |  |  |  |  |  | $— |  | $— |  |  |  |
Interest cost | 5 |  | 5 |  |  |  |  |  | 1 |  | 1 |  |  |  |
Expected return on plan assets | (7) |  | (7) |  |  |  |  |  | (1) |  | (1) |  |  |  |
Amortization of actuarial loss | 2 |  | 3 |  |  |  |  |  | — |  | — |  |  |  |
| $1 |  | $2 |  |  |  |  |  | $— |  | $— |  |  |  |
| Defined Benefit Pension Plans |  | OPEB Plans
WPL | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Interest cost | $5 |  | $5 |  |  |  |  |  | $1 |  | $1 |  |  |  |
Expected return on plan assets | (6) |  | (5) |  |  |  |  |  | — |  | — |  |  |  |
Amortization of actuarial loss | 3 |  | 3 |  |  |  |  |  | — |  | — |  |  |  |
| $2 |  | $3 |  |  |  |  |  | $1 |  | $1 |  |  |  |
NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Compensation expense | $4 |  | $3 |  |  |  |  |  | $2 |  | $2 |  |  |  |  |  | $2 |  | $1 |  |  |  |
Income tax benefits | 1 |  | 1 |  |  |  |  |  | 1 |  | — |  |  |  |  |  | — |  | — |  |  |  |
As of March 31, 2024, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $22 million, $11 million and $10 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the three months ended March 31, 2024, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.
|  |  | Weighted Average
| Grants |  | Grant Date Fair Value
Performance shares (total shareowner return metric) | 123,098 |  | $46.04
Performance shares (net income and diversity metrics) (formerly granted as performance restricted stock units) | 140,683 |  | 48.40
Restricted stock units | 120,557 |  | 48.40
As of March 31, 2024, 242,680 shares were included in the calculation of diluted EPS related to the nonvested equity awards.
WPL [Member] |
Benefit Plans | BENEFIT PLANS NOTE 10(a) Pension and OPEB Plans - Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are 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.
| Defined Benefit Pension Plans |  | OPEB Plans
Alliant Energy | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Service cost | $1 |  | $1 |  |  |  |  |  | $— |  | $1 |  |  |  |
Interest cost | 11 |  | 11 |  |  |  |  |  | 2 |  | 2 |  |  |  |
Expected return on plan assets | (13) |  | (13) |  |  |  |  |  | (1) |  | (1) |  |  |  |
Amortization of actuarial loss | 6 |  | 7 |  |  |  |  |  | — |  | — |  |  |  |
| $5 |  | $6 |  |  |  |  |  | $1 |  | $2 |  |  |  |
| Defined Benefit Pension Plans |  | OPEB Plans
IPL | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Service cost | $1 |  | $1 |  |  |  |  |  | $— |  | $— |  |  |  |
Interest cost | 5 |  | 5 |  |  |  |  |  | 1 |  | 1 |  |  |  |
Expected return on plan assets | (7) |  | (7) |  |  |  |  |  | (1) |  | (1) |  |  |  |
Amortization of actuarial loss | 2 |  | 3 |  |  |  |  |  | — |  | — |  |  |  |
| $1 |  | $2 |  |  |  |  |  | $— |  | $— |  |  |  |
| Defined Benefit Pension Plans |  | OPEB Plans
WPL | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Interest cost | $5 |  | $5 |  |  |  |  |  | $1 |  | $1 |  |  |  |
Expected return on plan assets | (6) |  | (5) |  |  |  |  |  | — |  | — |  |  |  |
Amortization of actuarial loss | 3 |  | 3 |  |  |  |  |  | — |  | — |  |  |  |
| $2 |  | $3 |  |  |  |  |  | $1 |  | $1 |  |  |  |
NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |  |  | 2024 |  | 2023 |  |  |  |
Compensation expense | $4 |  | $3 |  |  |  |  |  | $2 |  | $2 |  |  |  |  |  | $2 |  | $1 |  |  |  |
Income tax benefits | 1 |  | 1 |  |  |  |  |  | 1 |  | — |  |  |  |  |  | — |  | — |  |  |  |
As of March 31, 2024, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $22 million, $11 million and $10 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. For the three months ended March 31, 2024, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.
|  |  | Weighted Average
| Grants |  | Grant Date Fair Value
Performance shares (total shareowner return metric) | 123,098 |  | $46.04
Performance shares (net income and diversity metrics) (formerly granted as performance restricted stock units) | 140,683 |  | 48.40
Restricted stock units | 120,557 |  | 48.40
As of March 31, 2024, 242,680 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

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- Definition The entire disclosure for an entity's employee compensation and benefit plans, including, but not limited to, postemployment and postretirement benefit plans, defined benefit pension plans, defined contribution plans, non-qualified and supplemental benefit plans, deferred compensation, share-based compensation, life insurance, severance, health care, unemployment and other benefit plans. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 710 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org//710/tableOfContent Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 712 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org//712/tableOfContent Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 715 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org//715/tableOfContent Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 718 -Name Accounting Standards Codification -Publisher FASB -URI https://asc.fasb.org//718/tableOfContent + Details
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