Exhibit 12.2

INTERSTATE POWER AND LIGHT COMPANY

RATIO OF EARNINGS TO FIXED CHARGES AND RATIO OF EARNINGS TO COMBINED FIXED CHARGES

AND PREFERRED DIVIDEND REQUIREMENTS



|                                                                                |  |                             |      |      |                      |       |      |  |      |       |      |   |       |  |      |       |  |   |       |  |   |      
|------------------------------------------------------------------------------- |  | --------------------------- | ---- | ---- | -------------------- | ----- | ---- |  | ---- | ----- | ---- | - | ----- |  | ---- | ----- |  | - | ----- |  | - | -----
|                                                                                |  | Three MonthsEnded March 31, |      |      | Years Ended Dec. 31,
|                                                                                |  | 2010                        |      | 2009 |                      |       | 2009 |  | 2008 |       | 2007 |   | 2006  |  | 2005
|                                                                                |  | (dollars in millions)      
|EARNINGS:                                                                       |  |                             |      |      |                      |       |      |  |      |       |      |   |       |  |      |       |  |   |       |  |   |      
|Net income                                                                      |  | $                           | 9.7  |      | $                    | 41.7  |      |  | $    | 153.0 |      | $ | 141.6 |  | $    | 290.3 |  | $ | 172.4 |  | $ | 165.1
|Income tax expense (benefit) (a)                                                |  |                             | 9.9  |      |                      | (26.5 | )    |  |      | 27.0  |      |   | 52.6  |  |      | 186.8 |  |   | 69.4  |  |   | 80.8 
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|Income before income taxes                                                      |  |                             | 19.6 |      |                      | 15.2  |      |  |      | 180.0 |      |   | 194.2 |  |      | 477.1 |  |   | 241.8 |  |   | 245.9
|                                                                                |  |                             |      |      |                      |       |     
|Fixed charges as defined                                                        |  |                             | 20.6 |      |                      | 18.1  |      |  |      | 77.5  |      |   | 63.7  |  |      | 65.8  |  |   | 73.3  |  |   | 72.5 
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|Total earnings as defined                                                       |  | $                           | 40.2 |      | $                    | 33.3  |      |  | $    | 257.5 |      | $ | 257.9 |  | $    | 542.9 |  | $ | 315.1 |  | $ | 318.4
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|                                                                                |  |                             |      |      |                      |       |     
|FIXED CHARGES:                                                                  |  |                             |      |      |                      |       |      |  |      |       |      |   |       |  |      |       |  |   |       |  |   |      
|Interest expense                                                                |  | $                           | 20.3 |      | $                    | 17.7  |      |  | $    | 76.5  |      | $ | 61.9  |  | $    | 64.3  |  | $ | 71.8  |  | $ | 67.7 
|Estimated interest component of rent expense                                    |  |                             | 0.3  |      |                      | 0.4   |      |  |      | 1.0   |      |   | 1.8   |  |      | 1.5   |  |   | 1.5   |  |   | 4.8  
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|Total fixed charges as defined                                                  |  | $                           | 20.6 |      | $                    | 18.1  |      |  | $    | 77.5  |      | $ | 63.7  |  | $    | 65.8  |  | $ | 73.3  |  | $ | 72.5 
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|                                                                                |  |                             |      |      |                      |       |     
|Ratio of Earnings to Fixed Charges                                              |  |                             | 1.95 |      |                      | 1.84  |      |  |      | 3.32  |      |   | 4.05  |  |      | 8.25  |  |   | 4.30  |  |   | 4.39 
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|                                                                                |  |                             |      |      |                      |       |     
|Preferred dividend requirements (pre-tax basis) (b)                             |  | $                           | 7.9  |      | $                    | 1.4   |      |  | $    | 18.1  |      | $ | 21.1  |  | $    | 25.3  |  | $ | 21.6  |  | $ | 22.9 
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|                                                                                |  |                             |      |      |                      |       |     
|Fixed charges and preferred dividend requirements                               |  | $                           | 28.5 |      | $                    | 19.5  |      |  | $    | 95.6  |      | $ | 84.8  |  | $    | 91.1  |  | $ | 94.9  |  | $ | 95.4 
|                                                                                |  |                             |      |      |                      |       |      |  |      |      
|                                                                                |  |                             |      |      |                      |       |     
|Ratio of Earnings to Combined Fixed Charges and Preferred Dividend Requirements |  |                             | 1.41 |      |                      | 1.71  |      |  |      | 2.69  |      |   | 3.04  |  |      | 5.96  |  |   | 3.32  |  |   | 3.34 
|                                                                                |  |                             |      |      |                      |       |      |  |      |      



|(a) | Includes net interest related to unrecognized tax benefits.
|--- | -----------------------------------------------------------



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