Track lights provide directable beams of high-quality light for use in retail displays, galleries, museums, and residences. They are useful in locations where lights need to be aimed at different angles and where the position of the light may be changed frequently. Until recently, the only light sources that could provide the right kind of illumination for track lighting were inefficient halogen lamps. However, the introduction of low-wattage, metal halide (MH) lamps in the mid-1990s gave designers and specifiers an energy-efficient alternative. These lamps not only reduce energy use but last several times longer than halogen lamps, thus leading to reduced lamp-replacement costs as well. However, costs for MH lamps and fixtures are significantly higher than those for incandescent units, so MH products are most cost-effective in applications with long burn hours and where changing lamps is difficult.

Lamp types. Halogen lamps, compact fluorescent lamps (CFLs), and MH lamps are all used in track lighting (Table 1). Halogen lamps are the best choice if deep levels of dimming are required. CFLs are not a good choice if concentrated beams of light are needed, but these lamps are suitable for flood distributions and wall-washing.

MH lamps, especially those using ceramic arc tubes, have improved a great deal in recent years and can compete with halogen lamps in most applications except those where deep dimming is called for. MH lamps provide good color quality, long life, and a widening variety of lamp shapes and sizes, including MR16, PAR 20, and PAR 30. Ceramic metal halide (CMH) lamps offer better color quality and suffer from less color shifting than conventional quartz MH lamps, and they also maintain their light output better. The recent introduction of CMH lamps that draw as little as 20 watts (W) enables the technology to compete with halogen lamps and CFLs in a wider range of applications (Table 2).

Ballast types. Both magnetic and electronic ballasts are available for MH track lighting (see the topic "Metal Halide Ballasts"). Electronic ballasts are lighter and smaller than their magnetic counterparts and require less power, but they cost more. Some electronic ballasts also provide continuous dimming capability down to about 50 percent of initial power; magnetic ballasts only offer step-dimming capabilities.

Fixture types. Track lights for MH lamps are similar to track lights for halogen lamps (see Figure 1). The track can be recessed into the ceiling, mounted to the surface of the ceiling, or suspended from the ceiling in a configuration known as a pendant mount. The track head—which includes the lamp housing, lamp, socket, and a reflector cone—moves along the track and may be integrated into the track or suspended in a pendant mount. In addition, some individual track lights can be connected directly to a junction box. Ballasts are typically housed in the track head, although they may also be recessed into the ceiling plenum. Track lights also offer options for switching individual lamps or groups of lamps.

Accessories available for track lights include lenses that alter the beam shape, louvers and tubular shields that cut down on glare, and filters that change the color of the light. Some products also offer a ballast fuse that prevents damage from voltage surges.

Compare the cost-effectiveness of halogen with MH and other energy-efficient alternatives. The cost-effectiveness of MH track lights, or other alternatives such as CFLs, depends on the intensity of their use and on local electricity costs. MH lamps' energy efficiency and long life make up for higher first costs most quickly in areas where electricity costs are highest and in applications where maintenance costs are high and usage is most intense. Use the online calculator below as a screening tool to compare the costs and savings of halogen with energy-efficient alternatives for a given application.

Metal Halide Track Lighting Savings Calculator

Try before you buy. MH lamps produce different color effects than halogen lamps, so test the lighting before any major conversion to be sure that the results are acceptable. In addition, because ballasted fixtures (unlike halogen fixtures) are designed to work with only one lamp wattage, it is important to determine the right lamp size before you purchase any fixtures.

Account for lumen depreciation when specifying an MH system. MH lamps lose 10 to 40 percent of their rated output after 40 percent of their rated life; halogen lamps lose less than 5 percent. This phenomenon can shorten the lamp's effective life if output becomes too dim for the application, or it can force designers to overlight the application when it is first installed.

If ultraviolet (UV) radiation could cause problems, take steps to minimize UV output. Conventional quartz MH lamps emit UV radiation—mostly in the longer, less biologically harmful wavelengths—that can, over time, damage sensitive fabrics, papers, and artifacts. Special filtering can help prevent damage: Some MH track lights are available with special attachments to hold the filters. Ceramic MH lamps have built-in UV-blocking systems and emit much lower levels of UV than the quartz products.

Use MH lamps where heat is a problem. MH lamps emit much less infrared radiation than do incandescent lamps, which keeps the illuminated subject cooler. This feature can reduce fading and drying of objects and may increase the lifetimes of some displayed objects, such as food.

Don't use MH lamps where warm-up and restrike delays could cause problems. MH lamps require a warm-up period, which can be troublesome after power interruptions or in applications where lights are frequently turned on and off. Ceramic MH lamps on electronic ballasts take 1 to 3 minutes to reach full output and as much as 10 to 20 minutes to restrike (after a shutdown or power interruption).

Be sure the track can handle the weight in a retrofit. MH track lights can fit into existing tracks that were designed for halogen fixtures. However, magnetically ballasted MH track lights weigh considerably more than halogen units and could exceed the weight capacity of the track. Electronically ballasted fixtures weigh considerably less and may not present such a hazard.

Light-emitting diode (LED) technology, which can be applied to track lighting, is improving rapidly. Retail accent lighting is a growing area for LEDs, because LEDs provide the ability to vary color, create sparkle, and aim the light precisely. LED lamps are still expensive, but for color applications they are more efficient than filtered incandescent lights and offer long life. LEDs are also safer for illuminating sensitive items such as fabrics and paintings in art galleries because they can provide illumination free of UV and infrared energy. LEDs are still too expensive and inefficient for general illumination purposes.