Exhibit 12.4 West Texas Utilities Company Ratio of Earnings to Fixed Charges For Years Ended December 31, 1998 1997 1996 1995 1994 --------------------------------------------------- (thousands, except ratios) Operating income $59,365 $44,567 $51,734 $59,486 $54,763 Adjustments Income taxes 28,088 11,294 6,547 6,456 7,900 Provision for deferred income taxes (6,578) (954) 5,718 1,971 8,377 Deferred investment tax credits (1,321) (1,321) (1,321) (1,321) (1,321) Charges for investments and plant development costs, net of tax -- -- (10,946) -- -- Other income and deductions 2,034 1,237 601 (463) 4,210 Allowance for borrowed and equity funds used during construction 1,347 920 1,276 1,031 474 --------------------------------------------------- Earnings $82,935 $55,743 $53,609 $67,160 $74,403 =================================================== Fixed charges: Interest on long-term debt $20,352 $20,352 $21,169 $21,413 $18,547 Interest on short-term debt & other 4,580 4,911 4,925 4,111 3,534 =================================================== Fixed Charges $24,932 $25,263 $26,094 $25,524 $22,081 =================================================== Ratio of earnings to fixed charges 3.33 2.21 2.05 2.63 3.37 4-17