Among the few major, broad categories of light bulbs, High Intensity Discharge (HID) is the one most people know the least about. It is, however, the best option for energy saving an long life. The technology involved in HID lighting is similar to fluorescent lighting. An arc is established between two electrodes in a gas-filled tube which causes a special vapor to produce the light you see. Unlike fluorescent bulbs, this light does not need a coating of phosphors in order to produce the light.
There are three main types of HID lamps: mercury vapor, sodium, and metal halide. This article deals with metal halide bulbs. Some of the names you may be familiar with in this type of bulb are Sylvania Metalarc (Metal Arc), Sylvania Pro-Tech, GE Multi-Vapor (Multi Vapor), GE PulseArc (Pulse Arc), GE StayBright (Stay Bright), GE SPXX, Philips MasterColor (Master Color), Philips Econ-o-Watt, and Philips Pulse Start. All manufacturers also provide metal halide bulbs in the double-ended variety.
One of the chief benefits of metal halide lighting is energy efficiency. The lumen or light output from one of these bulbs is equivalent to the output from a normal incandescent bulb many times the wattage. Another key feature is that these bulbs will last a very long time. The average life of a standard model is typically about 20,000 hours. Compare this to a classic style bulb, which has an average life of about 1,000 hours. It is easy to see the energy savings (thus cost savings) that metal halide bulbs provide.
The factors discussed in the previous paragraph would not matter much to your business if the quality of the light was poor, if the light output was bland, dim, and strangely colored. Well, there is no need to worry about such things with metal halide bulbs. The color output is bright and white. This is the reason that metal halide bulbs are so popular in stores such as Target or Home Depot. Next time you are in your local store, take a look at the lighting; it is a good bet that the main source of light in the store is metal halide light bulbs.
All HID bulbs are designed to be matched with the appropriate ballast. This means that the bulbs are not interchangeable with one another. A metal halide cannot be swapped with a mercury vapor, a 175 watt metal halide cannot be swapped with a 400 watt metal halide, etc.
Some of the most common varieties of metal halide bulbs are as follows: 70 watt (M70, MH70, MVR70, MP70), 100 watt (M100, MH100, MVR100), 175 watt (M175, MH175, MVR175, MP175), 250 watt (M250, MH250, MVR250, MP250), 360 watt (MS360), 400 watt (M400, MH400, MVR400, MP400), and 1000 watt (M1000, MH1000, MVR1000, MP1000). Of course, there are other far less common wattages, shapes, and sizes available.