No franchise shall be granted by the city for a term exceeding twenty years and no exclusive franchise shall ever be granted. Each franchise shall include a provision requiring the franchise to take effect within one year after the adoption of the ordinance granting it. An irrevocable franchise and any extension to or amendments in such a franchise may be granted by the city only upon approval of at least three-fifths of the votes cast with respect to such proposition at a general or special election in the city. Such irrevocable franchise shall be subject to the conditions set forth in Section 13.5. An irrevocable franchise may be approved by the Council for referral to the electorate, only after a public hearing has been held thereon and after the grantee named therein has filed with City Clerk his unconditional acceptance of all terms of franchise. No special election for such purpose may be ordered by the Council, unless the estimated expense of holding such election has first been paid to the fiscal officer of the city by the grantee. In case a balance remains in the amount paid, after the expenses of the election are deducted therefrom, such balance shall be repaid to the grantee.