All suppliers of electricity, including public power districts, public power and irrigation districts, individual municipalities, registered groups of municipalities, electric membership associations, and cooperatives, shall have authority to enter into written agreements with each other limiting the areas in which or the customers to which a party to the agreement shall provide or sell electric energy at wholesale. Wholesale electric energy is hereby defined as electric energy which is sold to another agency for resale to the ultimate user, hereafter referred to as the retail customer. Before such agreements shall become effective, they shall be submitted to and approved by the Nebraska Power Review Board created by section 70-1003. It is declared to be the purpose of this section to promote and encourage the making of such agreements. Such agreements may be amended by the parties thereto at any time, and such amendments shall require the prior approval of the Nebraska Power Review Board. When requested to approve such an agreement or amendment thereto, the Nebraska Power Review Board shall consider whether or not the proposed agreement or amendment can be reasonably expected to provide a reliable wholesale power supply at a reasonable cost for the area covered by the agreement. It may make such investigation as it determines is necessary and hold a hearing if it determines one to be desirable. At the conclusion of its investigation, the Nebraska Power Review Board shall approve the agreement or amendment unless it determines that it cannot be reasonably expected to provide a reliable wholesale power supply at a reasonable cost for the area covered. Such agreements when approved by the Nebraska Power Review Board shall not be binding upon other suppliers that are not parties to the agreement and the Nebraska Power Review Board shall have no authority to impose conditions that will be binding or applicable to other suppliers that are not parties to such agreements. Such agreements shall not be considered as establishing service areas within the meaning of Chapter 70, article 10.