**PUBLIC      SERVICE COMPANY OF OKLAHOMA**

**Computation      of Ratios of Earnings to Fixed Charges **

**(in      thousands except ratio data)**

|                                                                                                             |   | **Year                Ended December 31,** |    |
|------------------------------------------------------------------------------------------------------------------|--------|--------------------------------------------|---------|
|                                                                                                             |   | **2001**                                   |    | **2002** |   | **2003** |   | **2004** |   | **2005** |   |
| **EARNINGS**                                                                                                     |   |                                  |    |    |   |    |   |    |   |    |   |
| Income                Before Income Taxes                                                                        |   | $                                          | 92,624  |   | $ | 63,443 |   | $ | 91,728 |   | $ | 45,351 |   | $ | 88,378 |   |
| Fixed              Charges (as below)                                                                            |   |                                       | 46,156  |   |   | 42,377 |   |   | 46,787 |   |   | 39,475 |   |   | 36,762 |   |
| **Total                Earnings**                                                                                |   | $                                          | 138,780 |   | $ | 105,820 |   | $ | 138,515 |   | $ | 84,826 |   | $ | 125,140 |   |
|                                                                                                             |   |                                       |    |   |   |   |   |   |   |   |   |   |   |   |   |   |
| **FIXED                CHARGES**                                                                                 |   |                                       |    |   |   |   |   |   |   |   |   |   |   |   |   |   |
| Interest                Expense                                                                                  |   | $                                          | 39,249  |   | $ | 40,422 |   | $ | 44,784 |   | $ | 37,957 |   | $ | 34,094 |   |
| Credit                for Allowance for Borrowed Funds Used                   During Construction |   |                                       | 5,570   |   |   | 673 |   |   | 451 |   |   | 280 |   |   | 668 |   |
| Trust Dividends                                                                                                  |   |                                       | -       |   |   | (186 | )  |   | (93 | ) |   | (62 | )  |   | - |   |
| Estimated              Interest Element in Lease Rentals                                                         |   |                                       | 1,337   |   |   | 1,468 |   |   | 1,645 |   |   | 1,300 |   |   | 2,000 |   |
| **Total                Fixed Charges**                                                                           |   | $                                          | 46,156  |   | $ | 42,377 |   | $ | 46,787 |   | $ | 39,475 |   | $ | 36,762 |   |
|                                                                                                             |   |                                       |    |   |   |   |   |   |   |   |   |   |   |   |   |   |
| **Ratio                of Earnings to Fixed Charges**                                                            |   |                                       | 3.00    |   |   | 2.49 |   |   | 2.96 |   |   | 2.14 |   |   | 3.40 |   |