Any irrigation district in this state which, pursuant to the authority conferred upon it by sections 46-301 to 46-315, shall own or operate, or hereafter acquire or establish any electric light and power plant, distribution system, or transmission lines, may extend and operate the same beyond its boundaries, and for that purpose is hereby authorized and empowered to construct, purchase, lease or otherwise acquire, and to maintain, improve, extend and operate electric light and power plants, distribution systems, and transmission lines outside the boundaries of such district, for such distance and over such territory within this state as may be deemed expedient. In the exercise of the powers granted by this section any such district by its board of directors may enter into contracts to furnish and sell electrical energy to any person, firm, association, public or private corporation, municipality or public electric light and power district. No such construction, purchase, lease, acquisition, improvement or extension of any such additional plant, distribution system, or transmission lines, however, shall be paid for except out of the net earnings and profits of one or more or all of the electric light and power plants, distribution systems, and transmission lines of such district. The provisions of this section shall be deemed cumulative and the authority herein granted shall not be limited or made inoperative by any other provision of law for the extension and financing of such plants, lines or systems.