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

|                                                    | Six Months            |                     
|--------------------------------------------------- | --------------------- | --------------------
|                                                    | Ended June 30,        | Years Ended Dec. 31,
|                                                    |                       |                     
|                                                    | 2009                  | 2008                
|                                                    |                       |                     
|                                                    | (dollars in millions)
|EARNINGS:                                           |                       |                     
|Net income                                          |                       | $61                 
|Income tax expense (benefit) (a)                    |                       | (19                 
|                                                    |                       |                     
|Income before income taxes                          |                       | 41                  
|Fixed charges as defined                            |                       | 36                  
|                                                    |                       |                     
|Total earnings as defined                           |                       | $78                 
|                                                    |                       |                     
|FIXED CHARGES:                                      |                      
|Interest expense                                    |                       | $35                 
|Estimated interest component of rent expense        |                       | 0                   
|                                                    |                       |                     
|Total fixed charges as defined                      |                       | $36                 
|                                                    |                       |                     
|Ratio of Earnings to Fixed Charges                  |                       | 2                   
|                                                    |                       |                     
|Preferred dividend requirements (pre-tax basis) (b) |                       | $5                  
|                                                    |                       |                     
|Fixed charges and preferred dividend requirements   |                       | $41                 
|                                                    |                       |                     
|Ratio of Earnings to Combined Fixed Charges and     |                      
|Preferred Dividend Requirements                     |                       | 1                   
|                                                    |                       |                     

(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.