Low-voltage halogen lamps are lamps that are operated at a voltage of 12 V. Because of the physics involved, the filament wire of a low-voltage lamp is five times as thick as that of a line voltage lamp of the same output. What�s more, the filament wire in a low-voltage lamp is only one fifth of the length of that in a comparable line voltage lamp. This means that the low-voltage filament can withstand much higher thermal loads. This in turn leads to higher luminous efficacy and much longer life than line voltage lamps.