EXHIBIT 12 PUBLIC SERVICE COMPANY OF OKLAHOMA Computation of Consolidated Ratios of Earnings to Fixed Charges (in thousands except ratio data) Twelve Months Year Ended December 31, Ended ----------------------------------------------- 1997 1998 1999 2000 2001 3/31/02 ---- ---- ---- ---- ---- ------- Operating Income $ 82,024 $115,074 $ 98,713 $ 96,669 $ 96,991 $ 97,060 Adjustments Income Taxes 12,313 52,494 18,562 10,291 54,408 58,850 Provision for Deferred Income Taxes 8,615 (1,651) 14,521 25,453 (17,751) (21,615) Deferred Investment Tax Credits (2,278) (1,795) (1,791) (1,791) (1,791) (1,791) Charges for Investments and Plant Development Costs, net of Tax (75) - - - - - Other Income and Deductions 729 (951) 745 8,739 (881) (1,128) Allowance for Borrowed and Equity Funds Used During Construction 2,317 2,029 1,636 4,631 6,471 3,995 -------- -------- -------- -------- -------- -------- Earnings $103,645 $165,200 $132,386 $143,992 $137,447 $135,371 ======== ======== ======== ======== ======== ======== Fixed Charges: Interest on Long-term Debt $30,474 $29,136 $26,528 $26,473 $29,305 $28,034 Interest on Short-term Debt 4,100 4,107 7,058 10,902 9,513 8,218 Distributions on Trust Preferred Securities 3,967 6,000 6,000 6,000 6,000 6,000 ------- ------- ------- ------- ------- ------- Fixed Chargess $38,541 $39,243 $39,586 $43,375 $44,818 $42,252 ======= ======= ======= ======= ======= ======= Ratio of Earnings to Fixed Charges 2.68 4.20 3.34 3.31 3.06 3.20 ==== ==== ==== ==== ==== ====