EXHIBIT 12 PUBLIC SERVICE COMPANY OF OKLAHOMA AND SUBSIDIARY Computation of Consolidated Ratios of Earnings to Fixed Charges (in thousands except ratio data) Year Ended December 31, 1998 1999 2000 2001 2002 Earnings: Net Income $ 76,909 $ 61,508 $ 66,663 $ 57,759 $ 41,060 Plus Federal Income Taxes 45,584 15,693 8,571 45,484 (43,956) Plus State Income Taxes 6,910 2,869 1,721 8,928 (7,529) Plus Provision for Deferred Income Taxes (1,651) 14,521 25,453 (17,751) 75,659 Plus Deferred Investment Tax Credits (1,795) (1,791) (1,791) (1,791) (1,791) Plus Fixed Charges (as below) 39,243 39,586 44,465 46,155 42,377 Total Earnings $165,200 $132,386 $145,082 $138,784 $105,820 Fixed Charges: Interest on Long-term Debt $ 29,136 $ 26,528 $ 26,473 $ 29,305 $ 28,401* Interest on Short-term Debt 4,107 7,058 10,902 9,513 6,508* Distributions on Trust Preferred Securities 6,000 6,000 6,000 6,000 6,000 Estimated Interest Element in Lease Rentals - - 1,090 1,337 1,468 Total Fixed Charges $ 39,243 $ 39,586 $ 44,465 $ 46,155 $ 42,377 Ratio of Earnings to Fixed Charges 4.20 3.34 3.26 3.00 2.49 * Certain amounts have been reclassified between interest on short-term and long-term debt compared to periods prior to January 1, 2002. This reclassification had no affect on the ratio.