Incandescent/Halogen Lamps 6 of 15

Incandescent filament life can be greatly increased or decreased by changing the current through the filament and therefore the temperature.

If a 130 volt lamp is operated at 120 volts a lower current will flow through the filament and therefore the lamp will operate at lower wattage. It will last longer but it will also produce less light. In some situation where labor and inconvenience associated with changing lamps is very high, this choice may make sense, but there are disadvantages: not only are the lamps burning at less watts than rated, they have also become less efficient in converting electricity into light (lower LPW).

Line overvoltage conditions can drastically reduce the life of incandescent lamp. In fact the 130 V lamp was designed originally for sites where voltages went higher than 120 frequently and customers were complaining about short life.