JUST AND REASONABLE RATES.

(a) The commission shall ensure that each rate a public utility or two or more public utilities jointly make, demand, or receive is just and reasonable. (b) A rate may not be unreasonably preferential, prejudicial, or discriminatory but must be sufficient, equitable, and consistent in application to each class of consumer. (c) A public utility may not: (1) grant an unreasonable preference or advantage concerning rates to a person in a classification; (2) subject a person in a classification to an unreasonable prejudice or disadvantage concerning rates; or (3) establish or maintain an unreasonable difference concerning rates between localities or between classes of service. (d) In establishing a public utility's rates, the commission may treat as a single class two or more municipalities that a public utility serves if the commission considers that treatment to be appropriate.