393.270.  Notice and hearing — order fixing price of gas, water, electricity or sewer service, or requiring improvement. — 1.  Before proceeding under a complaint presented as provided in sections 393.110 to 393.285, the commission shall cause notice of such complaint, and the purpose thereof, to be served upon the person or corporation affected thereby.  Such person or corporation shall have an opportunity to be heard in respect to the matters complained of at a time and place to be specified in such notice.  An investigation may be instituted by the commission as to any matter of which complaint may be made as provided in sections 393.110 to 393.285, or to enable it to ascertain the facts requisite to the exercise of any power conferred upon it.

  2.  After a hearing and after such investigation as shall have been made by the commission or its officers, agents, examiners or inspectors, the commission within lawful limits may, by order, fix the maximum price of gas, electricity, water or sewer service not exceeding that fixed by statute to be charged by such corporation or person, for the service to be furnished; and may order such improvement in the manufacture, distribution or supply of gas, in the manufacture, transmission or supply of electricity, in the distribution or supply of water, in the collection, carriage, treatment and disposal of sewage, or in the methods employed by such persons or corporation as will in its judgment be adequate, just and reasonable.

  3.  The price fixed by the commission under sections 393.110 to 393.285 shall be the maximum price to be charged by such corporation or person for gas, electricity or water for the service to be furnished within the territory and for a period to be fixed by the commission in the order, not exceeding three years, except in the case of a sliding scale, and thereafter until the commission shall, upon its own motion or upon the complaint of any corporation or person interested, fix a higher or lower maximum price of gas, electricity, water or sewer service to be thereafter charged.

  4.  In determining the price to be charged for gas, electricity, or water the commission may consider all facts which in its judgment have any bearing upon a proper determination of the question although not set forth in the complaint and not within the allegations contained therein, with due regard, among other things, to a reasonable average return upon capital actually expended and to the necessity of making reservations out of income for surplus and contingencies.

  5.  In determining the price to be charged for sewer service the commission may consider all facts which in its judgment have any bearing upon a proper determination of the question although not set forth in the complaint and not within the allegations contained therein, with due regard, among other things, to a reasonable average return upon the value of the property actually used in the public service and to the necessity of making reservations out of income for surplus and contingencies.