All public utility franchises shall make provision for fixing rates, fares and charges, and for readjustments thereof at periodic intervals of not more than five (5) years, either by arbitration upon terms to be specifically set forth in the franchise, or by any State agency, at the election of the Council. The value of the property of the utility used as a basis for fixing such rates, fares and charges shall in no event include a value predicated upon the franchise, good will or prospective profits.