Exhibit 12.1

ALLIANT ENERGY CORPORATION

RATIO OF EARNINGS TO FIXED
CHARGES

|                                                                   | Three Months          |      
|------------------------------------------------------------------ | --------------------- | -----
|                                                                   | Ended March 31,       |      
|                                                                   |                       |      
|                                                                   | 2006                  | 2005 
|                                                                   |                       |      
|                                                                   | (dollars in millions)
|EARNINGS:                                                          |                       |      
|Income from continuing operations                                  | $13.1                 | $26.7
|Income tax expense (benefit)                                       | 0.8                   | 9.6  
|                                                                   |                       |      
|Income from continuing operations before income taxes              | 13.9                  | 36.3 
|Fixed charges as defined                                           | 51.7                  | 58.9 
|Adjustment for undistributed equity earnings                       | (8.4)                 | (2.3)
|Less:                                                             
|Interest capitalized                                               | -                     | 2.1  
|Preferred dividend requirements of subsidiaries (pre-tax basis) ** | 4.9                   | 6.1  
|                                                                   |                       |      
|Total earnings as defined                                          | $52.3                 | $84.7
|                                                                   |                       |      
|FIXED CHARGES:                                                    
|Interest expense                                                   | $39.7                 | $44.0
|Interest capitalized                                               | -                     | 2.1  
|Estimated interest component of rent expense                       | 7.1                   | 6.7  
|Preferred dividend requirements of subsidiaries (pre-tax basis) ** | 4.9                   | 6.1  
|                                                                   |                       |      
|Total fixed charges as defined                                     | $51.7                 | $58.9
|                                                                   |                       |      
|Ratio of Earnings to Fixed Charges (Unaudited) ***                 | 1.01                  | 1.44 
|                                                                   |                       |      

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

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

***  The ratio calculation in the
above table relates to Alliant Energy Corporation's (Alliant Energy's) continuing
operations.  Refer to Note 11 of Alliant Energy's "Notes to Condensed Consolidated
Financial Statements" in Alliant Energy's Form 10-Q for the quarterly period ended March
31, 2006 for information related to Alliant Energy's discontinued operations.