Indiana Code Title 13. Environment § 13-26-11-9

(1) produce sufficient revenue to pay all expenses incident to the operation of the works, including maintenance cost, operating charges, upkeep, repairs, and interest charges on bonds or other obligations;

(2) produce sufficient revenue to provide the sinking fund for the liquidation of bonds or other evidence of indebtedness and reserves against default in the payment of interest and principal of bonds;

(3) produce sufficient revenue to provide adequate money to be used as working capital, as well as money for making improvements, additions, extensions, and replacements;  and

(4) give due consideration to the interests of the ratepayers.