(a) Rates shall not be unreasonably preferential, prejudicial, or discriminatory, but shall be sufficient, equitable, and consistent in application to each class of customers, and shall be based on cost.
(b) Rates will be determined using revenues, billing and usage data for a historical test year adjusted for known and measurable changes, and costs of service as defined in §25.231 of this title (relating to Cost of Service).

Source Note: The provisions of this §25.234 adopted to be effective July 5, 1999, 24 TexReg 4998