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

| Nine Months Ended |  |  |  |  |  |
| September 30, |  | Years Ended December 31,
| 2012 |  | 2011 |  | 2011 | 2010 | 2009 | 2008 | 2007
| (dollars in millions)
EARNINGS: |  |  |  |  |  |  |  |  |
Net income |  | $124.6 |  |  |  | $129.5 |  |  |  | $139.3 |  |  | $143.4 |  |  | $153.0 |  |  | $141.6 |  |  | $290.3 |
Income tax expense (benefit) (a) | (6.6 | ) |  | (2.2 | ) |  | (3.6 | ) | 42.3 |  | 27.0 |  | 52.6 |  | 186.8 |
Income before income taxes | 118.0 |  |  | 127.3 |  |  | 135.7 |  | 185.7 |  | 180.0 |  | 194.2 |  | 477.1 |
Fixed charges as defined | 59.5 |  |  | 59.8 |  |  | 79.6 |  | 83.1 |  | 77.5 |  | 63.7 |  | 65.8 |
Total earnings as defined |  | $177.5 |  |  |  | $187.1 |  |  |  | $215.3 |  |  | $268.8 |  |  | $257.5 |  |  | $257.9 |  |  | $542.9 |
FIXED CHARGES: |  |  |  |  |  |  |  |  |
Interest expense |  | $58.8 |  |  |  | $59.2 |  |  |  | $78.7 |  |  | $82.2 |  |  | $76.5 |  |  | $61.9 |  |  | $64.3 |
Estimated interest component of rent expense | 0.7 |  |  | 0.6 |  |  | 0.9 |  | 0.9 |  | 1.0 |  | 1.8 |  | 1.5 |
Total fixed charges as defined |  | $59.5 |  |  |  | $59.8 |  |  |  | $79.6 |  |  | $83.1 |  |  | $77.5 |  |  | $63.7 |  |  | $65.8 |
Ratio of Earnings to Fixed Charges | 2.98 |  |  | 3.13 |  |  | 2.70 |  | 3.23 |  | 3.32 |  | 4.05 |  | 8.25 |
Preferred dividend requirements (pre-tax basis) (b) |  | $8.9 |  |  |  | $11.6 |  |  |  | $14.6 |  |  | $19.9 |  |  | $18.1 |  |  | $21.1 |  |  | $25.3 |
Fixed charges and preferred dividend requirements |  | $68.4 |  |  |  | $71.4 |  |  |  | $94.2 |  |  | $103.0 |  |  | $95.6 |  |  | $84.8 |  |  | $91.1 |
Ratio of Earnings to Combined Fixed Charges and Preferred Dividend Requirements | 2.60 |  |  | 2.62 |  |  | 2.29 |  | 2.61 |  | 2.69 |  | 3.04 |  | 5.96 |

(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.