In case the council shall declare that it is expedient for such city to acquire by purchase or to construct, as the case may be, works for the purpose of supplying such city and the inhabitants thereof, or either, with electric or other lights, then the council shall direct the board of public works to cause to be made and recorded in their proceedings an estimate of the expense thereof, and the question of raising the amount required for such purpose shall be submitted to the electors of the city at its annual election, or at a special election called for that purpose by the council, as provided in this act, and shall be determined as 2/3 of the electors voting at such election by ballot shall decide.