High Intensity Discharge lighting (HID) is the best option for saving energy and long life. The technology involved in HID lighting is similar to fluorescent lighting in this manner: 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 sodium bulbs. Within the sodium category, there are high pressure sodium (HPS) and low pressure sodium bulbs (LPS). Some of the names you may be familiar with in this type of bulb are Sylvania Lumalux, GE Lucalox, Philips Ceramalux ALTO, Philips Ceramalux Comfort, and Westinghouse High Pressure Sodium. They are often associated with parking lot lighting and warehouse lighting, among others. They are used in high bay light fixtures in office/medical facilities.
One of the chief benefits of sodium light bulbs 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. This will save the end user a lot of money over the life of the bulb in energy. Speaking of the life of the bulbs, did you know the average life of a standard model is typically about 24,000 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 Sylvania high pressure sodium bulbs provide.
The drawbacks to sodium lighting are few, but important to consider. First of all, the initial cost of fixtures (which contain specialized ballasts) and the bulbs is much higher than normal incandescent lighting. Keep in mind the energy saved over the life of the bulb will more than make up for this, however. Second, the color rendering index (CRI) of this type of bulb is average at best. In other words, your new red shirt will not look as brilliant of a shade of red under this type of light. When color quality is important, you should consider installing Sylvania Metalarc metal halide 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 sodium cannot be swapped with a mercury vapor, a 100 watt sodium cannot be swapped with a 250 watt sodium, etc.
Some of the most common varieties of sodium bulbs are as follows: LU35, LU50, LU70, LU100, LU150, LU250, LU400, LU750, and LU1000. Of course, there are other far less common wattages, shapes, and sizes available. You can find them all available to order online right here at eLightBulbs.com.