Except as otherwise restricted by chapter 216B, the governing body, or the commission or board charged with the operation of the public utilities, if one exists therein, of any municipality in the state owning and operating an electric light and power plant for the purpose of the manufacture and sale of electrical power or for the purchase and redistribution of electrical power, may, upon a two-thirds vote of the governing body, or the commission or board, in addition to all other powers now possessed by such municipality, sell electricity to customers, singly or collectively, outside of such municipality, within the state but not to exceed a distance of 30 miles from the corporate limits of the municipality. Before any municipality shall have the power to extend its lines and sell electricity outside of the municipality as provided by sections 455.29 and 455.30, the governing body shall first submit to the voters of the municipality, at a general or special election, the general principle of going outside the municipality and fixing the maximum amount of contemplated expenditures reasonably expected to be made for any and all extensions then or thereafter contemplated. Three weeks' published notice shall be given of such election as required by law, and if a majority of those voting upon the proposition favors the same, then the municipality shall thereafter be considered as having chosen to enter the general business of extending its electric light and power facilities beyond the corporate limits of the municipality. It shall not be necessary to submit to a vote of the people the question of any specific enlargement, extension, or improvement of any outside lines; provided the voters of the municipality have generally elected to exercise the privileges afforded by sections 455.29 and 455.30, and, provided, that each and any specific extension, enlargement, or improvement project is within the limit of the maximum expenditure authorized at the election. In cities operating under a home rule charter, where a vote of the people is not now required in order to extend electric light and power lines, no election shall be required under the provisions of any act. At any election held to determine the attitude of the voters upon this principle, the question shall be simply stated upon the ballot provided therefor, and shall be substantially in the following form: "Shall the city of ..................... undertake the general proposition of extending its electric light and power lines beyond the limits of the municipality, and limit the maximum expenditures for any and all future extensions to the sum of $....................?" For this purpose every municipality is authorized and empowered to extend the lines, wires, and fixtures of its plant to such customers and may issue certificates of indebtedness therefor in an amount not to exceed the actual cost of the extensions and for a term not to exceed the reasonable life of the extensions. These certificates of indebtedness shall in no case be made a charge against the municipality, but shall be payable and paid out of current revenues of the plant other than taxes.