(in millions) PUBLIC SERVICE COMPANY OF OKLAHOMA STATEMENTS OF INCOME For the Years Ended December 31, 2020, 2019 and 2018 The common stock of PSO is wholly-owned by Parent. See Notes to Financial Statements of Registrants beginning on page 229. Years Ended December 31, 2020 2019 2018 REVENUES Electric Generation, Transmission and Distribution $ 1,246.1  $ 1,469.6  $ 1,537.6  Sales to AEP Affiliates 5.2  6.1  5.4  Other Revenues 14.8  6.1  4.3  TOTAL REVENUES 1,266.1  1,481.8  1,547.3  EXPENSES Fuel and Other Consumables Used for Electric Generation 15.6  195.1  240.5  Purchased Electricity for Resale 427.9  458.9  479.9  Other Operation 327.3  315.0  372.8  Maintenance 98.4  100.7  104.8  Depreciation and Amortization 173.5  169.5  164.0  Taxes Other Than Income Taxes 47.5  43.3  42.8  TOTAL EXPENSES 1,090.2  1,282.5  1,404.8  OPERATING INCOME 175.9  199.3  142.5  Other Income (Expense): Interest Income 0.1  1.2  0.1  Allowance for Equity Funds Used During Construction 4.0  2.7  0.4  Non-Service Cost Components of Net Periodic Benefit Cost 8.5  8.4  8.7  Interest Expense (60.3) (66.5) (63.5) INCOME BEFORE INCOME TAX EXPENSE 128.2  145.1  88.2  Income Tax Expense 5.2  7.5  5.0  NET INCOME $ 123.0  $ 137.6  $ 83.2  209