Utah Code § 54-3-1
All charges made, demanded or received by any public utility, or by any two or more public utilities, for any product or commodity furnished or to be furnished, or for any service rendered or to be rendered, shall be just and reasonable. Every unjust or unreasonable charge made, demanded or received for such product or commodity or service is hereby prohibited and declared unlawful. Every public utility shall furnish, provide and maintain such service, instrumentalities, equipment and facilities as will promote the safety, health, comfort and convenience of its patrons, employees and the public, and as will be in all respects adequate, efficient, just and reasonable. All rules and regulations made by a public utility affecting or pertaining to its charges or service to the public shall be just and reasonable. The scope of definition "just and reasonable" may include, but shall not be limited to, the cost of providing service to each category of customer, economic impact of charges on each category of customer, and on the well-being of the state of Utah; methods of reducing wide periodic variations in demand of such products, commodities or services, and means of encouraging conservation of resources and energy.
Utah Code § 54-3-1