- Commonly used lighting technologies include fluorescent, high-intensity discharge and LEDs.
- Fluorescents are suitable for indoor applications; HIDs are appropriate for high-bay and outdoor lighting.
- The use of LEDs is on the rise for general lighting applications.
Lighting accounts for about 20 percent of the total energy consumed in commercial buildings, making lighting a primary target for cost-saving upgrades. A number of factors can affect lighting choices, including the type of building, occupant traffic and occupancy schedules. Lighting types commonly used in commercial buildings include conventional fluorescents, high-intensity discharge (HID) lamps and newer, light-emitting diode (LED) technology.
Linear fluorescent lights commonly used in offices and other commercial and industrial facilities come in T12, T8 and T5 varieties. The T stands for tubular while the number refers to the diameter of the lamp in eighths of an inch. For example, a T8 lamp has a diameter of one inch or 8/8 of an inch. Most tubular fluorescent lamps use bi-pin bases that attach to the fixture. T12 and T8 lamps use the same medium bi-pin base while T5 models are slightly shorter and have a miniature bi-pin base. T8 and T5 lamps are more efficient because they are smaller in diameter and use electronic ballasts. Although standard T8 and T5 lamps have less light output than T12s, high-performance models are available.
Due to federal energy-efficiency regulations, T12 lamps are no longer being manufactured or imported for sale in the United States. Contact your lighting supplier for replacement options.
High-intensity discharge lamps
High-intensity discharge (HID) lamps are typically used for outdoor lighting or high-ceiling indoor applications. They generally require a warm-up time of several minutes and a cool-down time before restriking. Three commonly used HID lamps are characterized by their light-producing elements, including mercury vapor, metal halide and high-pressure sodium.
- Mercury Vapor. Mercury vapor is the oldest type of HID lighting and is used primarily for street lamps. Mercury vapor lamps have a long operating life but poor efficiency. To save energy, most mercury vapor lamps have been replaced by more efficient technologies.
- Metal Halide. Metal halide lamps include both metal halide (rare earth metal salts) and mercury gases. The addition of metal halide gases improves efficacy and color rendition.
- High-Pressure Sodium (HPS). HPS lamps use sodium as the main light-emitting element, along with a small amount of mercury. They generally have a yellow tint but can produce a warm, white light. They are widely used because of their long lifespan and high efficacy.
Light-emitting diodes (LEDs) are the latest in energy-efficient lighting. Long used in small electronics, they are becoming widely available for general indoor and outdoor lighting due to technology advances.
LEDs are highly energy efficient and have a long life, up to 50,000 hours or more. Made from solid materials, they are very durable and resistant to breakage. LEDs are dimmable and can start instantly, making them applicable with lighting controls and daylighting strategies.
As a new technology, LEDs typically cost more than conventional light sources and product standards and testing are still in development. The performance of LED products can vary widely.
Comparing lighting technologies
Lighting technologies have different operating characteristics and some are only suitable for certain applications. However, a direct comparison of their performance can still be helpful. The following table provides an overview of the efficacy, color rendition and estimated operating lifespan of each lighting type. Efficacy is measured in lumens per watt. Color rendition is quantified on a scale of 1 to 100 as color rendering index (CRI) where 100 CRI is equivalent to sunlight.
|Lighting Technology Comparison |
| Efficacy (lumens per watt) || CRI || Lifespan (hours) |
|Fluorescent || 30-110 ||50-90 || 7,000-30,000 |
|Metal Halide || 70-115 ||70-90 || 5,000-20,000 |
|High-Pressure Sodium || 50-114 || 25 || 16,000-24,000 |
|LED || 50-100 ||70-90 || 35,000-100,000 |
Fluorescent lights are energy efficient and have a long lifespan, but a relatively poor color rendition. HPS lamps compare favorably to metal halides in efficacy and have a much longer operating life, but they have a very poor color rendition. LED lights combine efficiency, long lifespan and good color rendition. As technology advances, the use of LEDs in a variety of applications should continue to grow.
Developing a Lighting Strategy
A successful lighting strategy involves much more than just an understanding of available lighting technologies. It includes proper design and maintenance, as well as the use of energy-saving controls. For lamps that contain hazardous materials, such as fluorescents, a lighting strategy should include a system for proper disposal.