Under such regulations as the commission may prescribe, every public utility shall file with the commission, within such time and in such form as the commission may designate, tariffs showing all rates established by it and collected or enforced, or to be collected or enforced, within the jurisdiction of the commission. The tariffs of any public utility also subject to the jurisdiction of a Federal regulatory body shall correspond, so far as practicable, to the form of those prescribed by such Federal regulatory body. Every public utility shall keep copies of such tariffs open to public inspection under such rules and regulations as the commission may prescribe. One copy of any rate filing shall be made available, at a convenient location and for a reasonable length of time within each of the utilities' service areas, for inspection and study by customers, upon request to the utility.