| Exhibit 12.1                                                                                                                                            |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|--------|-----------------------|--------|--------|----------------------|--------|--------|--------|--------|--------|--------|--------|--------|--------|--------|--------|----------|--------|--------|--------|--------|
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
| ALLIANT ENERGY CORPORATION                                                                                                                              |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
| RATIO OF EARNINGS TO FIXED CHARGES                                                                                                                      |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
|                                                                                                                                                    |   | Nine Months           |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |
|                                                                                                                                                    |   | Ended Sep. 30,        |   |   | Years Ended Dec. 31, |   |
|                                                                                                                                                    |   | 2009                  |   |   | 2008                 |   |   | 2008   |   |   | 2007   |   |   | 2006   |   |   | 2005 (a) |   |   | 2004   |   |
|                                                                                                                                                    |   | (dollars in millions) |   |
| EARNINGS:                                                                                                                                               |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
| Net income from continuing operations attributable to                                                                                                   |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |
|    Alliant Energy Corporation common shareowners                                                                                         |   | $                     | 58.4   |   |                 | $      | 229.0  |   |   | $      | 280.0  |   |   | $      | 424.7  |   |     | $      | 338.3  |   |   | $ | 56.4 |   |   | $ | 218.4 |   |
| Income tax expense (benefit) (b)                                                                                                                        |   |                  | (26.5  | )      |                 |   | 118.8  |   |   |   | 140.2  |   |   |   | 255.8  |   |     |   | 203.0  |   |   |   | (52.9 | ) |   |   | 91.2 |   |
| Subtotal                                                                                                                                                |   |                  | 31.9   |   |                 |   | 347.8  |   |   |   | 420.2  |   |   |   | 680.5  |   |     |   | 541.3  |   |   |   | 3.5 |   |   |   | 309.6 |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| Fixed charges as defined                                                                                                                                |   |                  | 147.8  |   |                 |   | 138.9  |   |   |   | 186.5  |   |   |   | 185.6  |   |     |   | 213.4  |   |   |   | 226.7 |   |   |   | 238.8 |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| Adjustment for undistributed equity earnings                                                                                                            |   |                  | (4.9   | )      |                 |   | (4.0   | )      |   |   | (6.1   | )      |   |   | (7.8   | )      |     |   | (16.6  | )      |   |   | (41.7 | ) |   |   | (21.0 | ) |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| Less:                                                                                                                                                   |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
|    Interest capitalized                                                                                                                  |   |                  | -      |   |                 |   | -      |   |   |   | -      |   |   |   | -      |   |     |   | -      |   |   |   | 3.4 |   |   |   | 5.4 |   |
|    Preferred dividend requirements of subsidiaries (pre-tax basis) (c)                                                                   |   |                  | 8.9    |   |                 |   | 20.8   |   |   |   | 27.5   |   |   |   | 29.5   |   |     |   | 29.3   |   |   |   | 5.5 |   |   |   | 25.9 |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| Total earnings as defined                                                                                                                               |   | $                     | 165.9  |   |                 | $      | 461.9  |   |   | $      | 573.1  |   |   | $      | 828.8  |   |     | $      | 708.8  |   |   | $ | 179.6 |   |   | $ | 496.1 |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| FIXED CHARGES:                                                                                                                                          |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| Interest expense                                                                                                                                        |   | $                     | 113.8  |   |                 | $      | 90.0   |   |   | $      | 125.8  |   |   | $      | 116.7  |   |     | $      | 145.7  |   |   | $ | 175.8 |   |   | $ | 176.9 |   |
| Interest capitalized                                                                                                                                    |   |                  | -      |   |                 |   | -      |   |   |   | -      |   |   |   | -      |   |     |   | -      |   |   |   | 3.4 |   |   |   | 5.4 |   |
| Estimated interest component of rent expense                                                                                                            |   |                  | 25.1   |   |                 |   | 28.1   |   |   |   | 33.2   |   |   |   | 39.4   |   |     |   | 38.4   |   |   |   | 42.0 |   |   |   | 30.6 |   |
| Preferred dividend requirements of subsidiaries (pre-tax basis) (c)                                                                                     |   |                  | 8.9    |   |                 |   | 20.8   |   |   |   | 27.5   |   |   |   | 29.5   |   |     |   | 29.3   |   |   |   | 5.5 |   |   |   | 25.9 |   |
| Total fixed charges as defined                                                                                                                          |   | $                     | 147.8  |   |                 | $      | 138.9  |   |   | $      | 186.5  |   |   | $      | 185.6  |   |     | $      | 213.4  |   |   | $ | 226.7 |   |   | $ | 238.8 |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| Ratio of Earnings to Fixed Charges (d)                                                                                                                  |   |                  | 1.12   |   |                 |   | 3.33   |   |   |   | 3.07   |   |   |   | 4.47   |   |     |   | 3.32   |   |   |   | 0.79 |   |   |   | 2.08 |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| (a) For the year ended Dec. 31, 2005, earnings as defined were inadequate to cover fixed charges as defined by $47.1 million.                           |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| (b) Includes net interest related to unrecognized tax benefits.                                                                                         |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| (c) Preferred dividend requirements of subsidiaries (pre-tax basis) are computed by dividing the preferred dividend requirements of subsidiaries by one |   |
| hundred percent minus the respective year-to-date effective income tax rate.                                                                            |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |
|                                                                                                                                                    |   |                  |   |   |                 |   |   |   |   |   |   |   |   |   |   |   |     |   |   |   |   |   |   |   |   |   |   |   |
| (d) The ratio calculation in the above table relates to Alliant Energy Corporation's continuing operations.                                        |   |