Exhibit 12.3

WISCONSIN POWER AND LIGHT COMPANY

RATIO OF EARNINGS TO FIXED CHARGES AND RATIO OF EARNINGS TO COMBINED FIXED CHARGES
    AND PREFERRED DIVIDEND REQUIREMENTS

|                                                    | Three Months          |      |                     
|--------------------------------------------------- | --------------------- | ---- | --------------------
|                                                    | Ended March 31,       |      | Years Ended Dec. 31,
|                                                    |                       |      |                     
|                                                    | 2009                  | 2008 |                     
|                                                    |                       |      |                     
|                                                    | (dollars in millions)
|EARNINGS:                                           |                       |      |                     
|Net income                                          |                       | $31  | .3                  
|Income taxes (a)                                    |                       | 13   | .7                  
|                                                    |                       |      |                     
|Income before income taxes                          |                       | 45   | .0                  
|Fixed charges as defined                            |                       | 21   | .3                  
|Adjustment for undistributed equity earnings        |                       | (2   | .2)                 
|                                                    |                       |      |                     
|Total earnings as defined                           |                       | $64  | .1                  
|                                                    |                       |      |                     
|FIXED CHARGES:                                      |                      
|Interest expense                                    |                       | $17  | .5                  
|Estimated interest component of rent expense        |                       | 3    | .8                  
|                                                    |                       |      |                     
|Total fixed charges as defined                      |                       | $21  | .3                  
|                                                    |                       |      |                     
|Ratio of Earnings to Fixed Charges                  |                       | 3.0  | 1                   
|                                                    |                       |      |                     
|Preferred dividend requirements (pre-tax basis) (b) |                       | $1   | .2                  
|                                                    |                       |      |                     
|Fixed charges and preferred dividend requirements   |                       | $22  | .5                  
|                                                    |                       |      |                     
|Ratio of Earnings to Combined Fixed Charges and     |                      
|Preferred Dividend Requirements                     |                       | 2.8  | 5                   
|                                                    |                       |      |                     

(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.