Such study shall assess, at a minimum, the following:
The Commission, in order to expedite the determination of rate questions, or to avoid unnecessary and unreasonable expense, or to avoid unjust or unreasonable discrimination between classes of customers, or, whenever in the judgment of the Commission public interest so requires, may, for rate making and accounting purposes, or either of them, consider one or more municipalities either with or without the adjacent or intervening rural territory as a regional unit where the same public utility serves such region under substantially similar conditions, and may within such region prescribe uniform rates for consumers or patrons of the same class.
Any public utility, with the consent and approval of the Commission, may as a basis for the determination of the charges made by it classify its service according to the amount used, the time when used, the purpose for which used, and other relevant factors.
220 ILCS 5/9-241