When granting to any individual, firm or corporation the right to furnish, distribute and sell electric energy to customers within such city, such grant shall be made only through the enactment of an ordinance for such purpose by the governing body of the city. The ordinance shall be read in full at three consecutive regular meetings of the governing body and published in full once each week for two consecutive weeks in the official city paper before becoming effective. The ordinance shall not grant the right to furnish and sell electric energy to more than one customer or grant the right to furnish and sell electric energy to any customer within the city for a period exceeding five years from the effective date of the ordinance.