Exhibit 12.1

ALLIANT ENERGY CORPORATION

RATIO OF
EARNINGS TO FIXED CHARGES



|                                                                                                    |  |                             |   |  |                      |   |  |        |   |  |        |   |  |        |   |  |        |   |  |         
|--------------------------------------------------------------------------------------------------- |  | --------------------------- | - |  | -------------------- | - |  | ------ | - |  | ------ | - |  | ------ | - |  | ------ | - |  | --------
|                                                                                                    |  | Three MonthsEnded March 31, |   |  | Years Ended Dec. 31,
|                                                                                                    |  | 2010                        |   |  | 2009                 |   |  | 2009   |   |  | 2008   |   |  | 2007   |   |  | 2006   |   |  | 2005 (a)
|                                                                                                    |  | (dollars in millions)      
|EARNINGS:                                                                                           |  |                             |   |  |                      |   |  |        |   |  |        |   |  |        |   |  |        |   |  |         
|Net income from continuing operations attributable to Alliant Energy Corporation common shareowners |  | $43.4                       |   |  | $72.6                |   |  | $110.7 |   |  | $280.0 |   |  | $424.7 |   |  | $338.3 |   |  | $56.4   
|Income tax expense (benefit) (b)                                                                    |  | 34.9                        |   |  | (18.9                | ) |  | (9.2   | ) |  | 140.2  |   |  | 255.8  |   |  | 203.0  |   |  | (52.9)  
|                                                                                                    |  |                             |   |  |                      |   |  |       
|Subtotal                                                                                            |  | 78.3                        |   |  | 53.7                 |   |  | 101.5  |   |  | 420.2  |   |  | 680.5  |   |  | 541.3  |   |  | 3.5     
|                                                                                                    |  |                             |   |  |                      |   | 
|Fixed charges as defined                                                                            |  | 52.0                        |   |  | 44.1                 |   |  | 200.7  |   |  | 186.5  |   |  | 185.6  |   |  | 213.4  |   |  | 226.7   
|                                                                                                    |  |                             |   |  |                      |   | 
|Adjustment for undistributed equity earnings                                                        |  | (1.3                        | ) |  | (2.2                 | ) |  | (6.7   | ) |  | (6.1   | ) |  | (7.8   | ) |  | (16.6  | ) |  | (41.7)  
|                                                                                                    |  |                             |   |  |                      |   | 
|Less:                                                                                               |  |                             |   |  |                      |   |  |        |   |  |        |   |  |        |   |  |        |   |  |         
|Interest capitalized                                                                                |  | -                           |   |  | -                    |   |  | -      |   |  | -      |   |  | -      |   |  | -      |   |  | 3.4     
|Preferred dividend requirements of subsidiaries (pre-tax basis) (c)                                 |  | 8.1                         |   |  | 3.6                  |   |  | 17.4   |   |  | 27.5   |   |  | 29.5   |   |  | 29.3   |   |  | 5.5     
|                                                                                                    |  |                             |   |  |                      |   |  |       
|Total earnings as defined                                                                           |  | $120.9                      |   |  | $92.0                |   |  | $278.1 |   |  | $573.1 |   |  | $828.8 |   |  | $708.8 |   |  | $179.6  
|                                                                                                    |  |                             |   |  |                      |   |  |       
|FIXED CHARGES:                                                                                      |  |                             |   |  |                      |   |  |        |   |  |        |   |  |        |   |  |        |   |  |         
|Interest expense                                                                                    |  | $40.7                       |   |  | $35.7                |   |  | $154.9 |   |  | $125.8 |   |  | $116.7 |   |  | $145.7 |   |  | $175.8  
|Interest capitalized                                                                                |  | -                           |   |  | -                    |   |  | -      |   |  | -      |   |  | -      |   |  | -      |   |  | 3.4     
|Estimated interest component of rent expense                                                        |  | 3.2                         |   |  | 4.8                  |   |  | 28.4   |   |  | 33.2   |   |  | 39.4   |   |  | 38.4   |   |  | 42.0    
|Preferred dividend requirements of subsidiaries (pre-tax basis) (c)                                 |  | 8.1                         |   |  | 3.6                  |   |  | 17.4   |   |  | 27.5   |   |  | 29.5   |   |  | 29.3   |   |  | 5.5     
|                                                                                                    |  |                             |   |  |                      |   |  |       
|Total fixed charges as defined                                                                      |  | $52.0                       |   |  | $44.1                |   |  | $200.7 |   |  | $186.5 |   |  | $185.6 |   |  | $213.4 |   |  | $226.7  
|                                                                                                    |  |                             |   |  |                      |   |  |       
|Ratio of Earnings to Fixed Charges (d)                                                              |  | 2.33                        |   |  | 2.09                 |   |  | 1.39   |   |  | 3.07   |   |  | 4.47   |   |  | 3.32   |   |  | 0.79    
|                                                                                                    |  |                             |   |  |                      |   |  |       

(a) For the year ended Dec. 31, 2005, earnings as defined
were inadequate to cover fixed charges as defined by $47.1 million.

(b) Includes net interest related to unrecognized tax benefits.

(c) Preferred dividend requirements of subsidiaries (pre-tax basis) are computed by dividing the preferred dividend requirements of
subsidiaries by one hundred percent minus the respective year-to-date effective income tax rate.

(d) The ratio calculation in the above table
relates to Alliant Energy Corporations continuing operations.