Multi-volt or multi-tap lighting transformers allow for multiple voltage outputs to compensate for voltage drop going out to the light fixtures. It is essential that halogen landscape light bulbs operate between 10.8 to 12 volts AC. Multi-volt landscape lighting transformers allow users to choose between various voltage taps to ensure the proper voltage is supplied to the bulb. Longer wire runs or higher wattage runs will require the use of higher voltage taps.