Metal halide lighting is a common type of HID (High Intensity Discharge) lighting used for many exterior and warehouse lights.
Metal halide lighting produces a white color - 3500-4000 kelvin temperature. The metal halide light bulbs generally last between 15-20K hours. Metal halide lights require a ballast to operate
There are two types of metal halide systems - probe-start and pulse-start. All lower wattage metal halide light bulbs (150 watt and below) are pulse-start. Higher wattage bulbs can be either pulse-start or probe-start. As of today most of higher wattage metal halide lights in existence are still the older style probe-start. However, as a result of the Energy Independence and Security act of 2007, all metal halide imported or manufactuered in the United States after January 1, 2009 with wattages between 150-500 must be pulse-start. At this point the older style probe-start metal halide bulbs and ballasts are still readily available and no plans appear to be in place by the US Government to phase out the replacement products.
It is important to note that pulse-start and probe-start bulbs are not interchangable. If the fixture has a probe-start ballast it must be equipped with a probe-start metal halide light bulb, and vice versa with pulse-start metal halide bulbs and ballasts.
Pulse-start metal halide is more energy efficient (approximatey 20%) and has a longer lifespan than traditional probe-start metal halide, plus it has a much better lumen maintenance curve (meaning the lights lose less initial lumens over time).
Probe-start metal halide fixtures can be retrofitted to pulse-start metal halide for energy savings. There are also Idaho Power lighting incentives for this type of lighting retrofit.