| 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                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |
|                                                                                                                              |   | Years Ended Dec.      31,  |   |
|                                                                                                                              |   | 2009                       |   |   | 2008   |   |   | 2007   |   |   | 2006   |   |   | 2005   |   |
|                                                                                                                              |   | (dollars in      millions) |   |
| EARNINGS:                                                                                                                         |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Net      income                                                                                                                   |   | $                          | 153.0  |   |   | $      | 141.6  |   |   | $      | 290.3  |   |   | $      | 172.4  |   |   | $ | 165.1 |   |
| Income taxes      (a)                                                                                                             |   |                       | 27.0   |   |   |   | 52.6   |   |   |   | 186.8  |   |   |   | 69.4   |   |   |   | 80.8 |   |
| Income before income      taxes                                                                                                   |   |                       | 180.0  |   |   |   | 194.2  |   |   |   | 477.1  |   |   |   | 241.8  |   |   |   | 245.9 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Fixed charges as      defined                                                                                                     |   |                       | 77.5   |   |   |   | 63.7   |   |   |   | 65.8   |   |   |   | 73.3   |   |   |   | 72.5 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Total earnings as      defined                                                                                                    |   | $                          | 257.5  |   |   | $      | 257.9  |   |   | $      | 542.9  |   |   | $      | 315.1  |   |   | $ | 318.4 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| FIXED      CHARGES:                                                                                                               |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Interest      expense                                                                                                             |   | $                          | 76.5   |   |   | $      | 61.9   |   |   | $      | 64.3   |   |   | $      | 71.8   |   |   | $ | 67.7 |   |
| Estimated interest      component of rent expense                                                                                 |   |                       | 1.0    |   |   |   | 1.8    |   |   |   | 1.5    |   |   |   | 1.5    |   |   |   | 4.8 |   |
| Total fixed charges      as defined                                                                                               |   | $                          | 77.5   |   |   | $      | 63.7   |   |   | $      | 65.8   |   |   | $      | 73.3   |   |   | $ | 72.5 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Ratio of Earnings to      Fixed Charges                                                                                           |   |                       | 3.32   |   |   |   | 4.05   |   |   |   | 8.25   |   |   |   | 4.30   |   |   |   | 4.39 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Preferred dividend      requirements (pre-tax basis) (b)                                                                          |   | $                          | 18.1   |   |   | $      | 21.1   |   |   | $      | 25.3   |   |   | $      | 21.6   |   |   | $ | 22.9 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Fixed charges and      preferred dividend requirements                                                                            |   | $                          | 95.6   |   |   | $      | 84.8   |   |   | $      | 91.1   |   |   | $      | 94.9   |   |   | $ | 95.4 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Ratio of Earnings to      Combined Fixed Charges and                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
|    Preferred      Dividend Requirements                                                                            |   |                       | 2.69   |   |   |   | 3.04   |   |   |   | 5.96   |   |   |   | 3.32   |   |   |   | 3.34 |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| (a)      Includes net interest related to unrecognized taxbenefits.                                                               |   |                       |   |   |   |   |   |   |   |   |   |   |   |
|                                                                                                                              |   |                       |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |
| (b)      Preferred dividend requirements (pre-tax basis) are computed by dividing      the preferred dividend requirements by one |   |
| hundred percent      minus the respective annual effective income tax rate.                                                       |   |                       |   |   |   |   |   |   |   |