220 ILCS 5/8-301
The Commission shall have power to ascertain, determine and fix for each kind of public utility suitable and convenient standard commercial units of service, product or commodity, which units shall be lawful units for the purposes of this Act; to ascertain, determine and fix adequate and serviceable standards for the measurements of quantity, quality, pressure, initial voltage or other condition pertaining to the performing of its service or to the furnishing of its product or commodity by any public utility, and to prescribe reasonable regulations for examining, measuring and testing such service, product or commodity, and to establish reasonable rules, regulations, specifications and standards to secure the accuracy of all meters and appliances for examining, measuring or testing such service, product or commodity. The Commission may purchase such materials, apparatus and standard measuring instruments as it deems necessary to carry out the provisions of this Section.
The Commission shall provide for the inspection of the manner in which every public utility conforms to the reasonable regulations prescribed by the Commission for examining, measuring and testing its service, product or commodity, and the Commission may supplement such inspections by examining, measuring and testing the service, product or commodity of any public utility. Any consumer or user may have tested any appliance for examining, measuring or testing any such service, product or commodity upon payment of the fees fixed by the Commission. The Commission shall declare and establish reasonable fees to be paid for examining and testing such appliances on the request of consumers or users, the fee to be paid by the consumer or user at the time of his request, but to be repaid to the consumer or user by the public utility if the measuring appliance be found unreasonably defective or incorrect to the disadvantage of the consumer or user.
The Commission, its officers, agents, experts or inspectors and employees shall have power to enter upon any premises occupied by any public utility for the purpose of making the examinations and tests provided in the Act, and set up and use on such premises, any apparatus and appliances and occupy reasonable space therefor.
All fees collected by the Commission under this Section shall be paid promptly after the receipt of the same, accompanied by a detailed statement of the same, into the Public Utility Fund in the State treasury.
220 ILCS 5/8-301