All agencies of the United States engaged in the generation and sale of electric energy for ultimate distribution to the public shall be subject, as to all facilities used for such generation and sale, and as to the electric energy sold by such agency, to the provisions of sections 825 and 825a of this title, so far as may be practicable, and shall comply with the provisions of such sections and with the rules and regulations of the Commission thereunder to the same extent as may be required in the case of a public utility.