Incandescent lamps are the most familiar source of light and are widely used in residential and other low-annual-hours-use applications. The popularity of the incandescent lamp is due to the simplicity with which it can be used and the low price of both the lamp and the fixture. Also, the lamp requires no special equipment, like a ballast, to modify the characteristics of its power supply. Incandescents are often used in commercial and industrial applications where the intended hours of use are low (less than 500 hours per year), where needed for aesthetic purposes, or where initial cost is an overriding criterion.

The most common types are: the "A" or arbitrary bulb-shaped lamp; the "PS"or pear-shaped lamp; the "R" or reflector lamp; the "PAR" or sealed-beam lamp,and the tungsten-halogen lamp.

Although incandescents are the least efficient light sources, their advantages assure them a place in most homes and businesses for the foreseeable future. Therefore, we should at least use the wisely and recognize ways to save money using them. For instance, knowing that the efficiency of incandescent lamps increases as lamp wattage increases can allow you to save energy. This makes it possible to save on both energy and fixture costs whenever you can use one higher wattage lamp instead of two lower wattage lamps. For example, one 100-watt lamp produces more light, 1740 lumens, than two 60-watt lamps (860 lumens each) for a total of 1,720 lumens. Whenever you can substitute one 100 watt lamp for two 60s, you save 20 watts. Beware though, read the fixture ratings. Some are rated for 60 watt or lower lamps.

The specific type of incandescent lamp used and the kind of fixture involved also make a difference. For example, a 75-watt ellipsoidal reflector lamp delivers more light in a stack-baffled downlight than a 150-watt R lamp. This is because much of the R lamp's light is trapped in the fixture and converted to heat. The 75-watt ER lamp's shape and reflective interior focuses light down, outside of the fixture, thereby producing more light on the surface.


  • Low initial cost
  • Excellent color rendition
  • Instant starting
  • Inexpensive dimming capability
  • Skin-flattering warm color
  • Small size, which allows it to be used in point fixtures, such as spot lamps
  • Wide variety of shapes, sizes, colors and wattages are available
  • Output unaffected by high or low ambient temperatures
  • Simple to operate and install
  • Requires no ballast
  • High brightness light source
  • Available in many colors

Variety of filament design possibilities offer optical control, accurate distribution patterns and critical service operation



  • Relatively short useful life with poor over-voltage tolerance. At 10% over voltage, life is reduced about 75%!
  • Very inefficient source of light. On average, less than 10% of the wattage goes to produce light; the remainder becomes heat.
  • High heat component can create hidden energy costs due to increased cooling needs.


Choosing the Right Lamp for the Application

Choosing the right lamp for a particular application can save energy and result in the highest quality of light. Unfortunately, in many cases a building manager will choose the cheapest lamp over the most appropriate lamp and the quality of the light is sacrificed.

For example, in a recessed down-lighting fixture the cheapest lamp may be an "A" and "PS" lamp, while a PAR or some type of reflectorized lamp makes more sense. The building manager will have to use a higher wattage "A" lamp in this fixture than a "PAR" or other reflector type lamp. The result is higher energy cost. These added energy costs often outweigh the cost savings in the lamp itself. Therefore, choosing the right lamp for the right application, sometimes costs more up front, but it will save money over the life of the lamp.


Technology Types (Resource)

The tungsten-halogen lamp, like the other incandescent lamps, uses a tungsten filament as the light source. Unlike others, however, the lamp's fill-gas is composed of a "family of elements" known as halogens. The halogens prevent lamp walls from darkening as quickly as those of other incandescent lamps, so more light is available to the task or work surface. In other words, the light output of tungsten-halogen lamps does not drop off as rapidly as the light output of other incandescent lamps.


General Service Lamps

General Service Lamps are the most common filament lamps. They range in size from the 15 watt A-15 to the 1500 watt PS-52. These lamps are designed for 120, 125, and 130 volt circuits and all are equipped with screw bases.

The larger wattages are manufactured in either clear or inside frosted bulbs, while the 200 watt and smaller bulbs are usually frosted.

High wattage lamps are used primarily in commercial and industrial applications. So-called Soft White lamps are popular in homes because they achieve maximum light diffusion from the filament without glare or harsh shadows.

Industrial Service Lamps

Industrial service lamps are similar to standard inside frosted lamps. The difference is they are specifically designed to meet the requirements of strength and long "in service" life. These characteristics are necessary in some industrial applications where normal shock and vibration are present. However, the increase in strength and life in Industrial Service lamps comes at a cost of reduced lamp efficiency.

Tungsten Halogen Lamps

Tungsten halogen lamps, which are commonly called "quartz" lamps, have been designed for general lighting and a number of other applications. They are known for their compact size, thermal shock resistance, high efficiency, long life, and excellent lumen maintenance. The tungsten halogen lamp features a regenerative cycle which keeps the bulb wall free from the normal tungsten blackening that occurs in other incandescent lamps.

Halogen lamps are available in a wide range of wattages. They are also available in a variety of sizes and shapes from the traditional "A" lamp to the "PAR" flood lamp. A special class of tungsten halogen lamps is available in low voltage and uses a small reflectorized bulb. These lamps have excellent beam spread control and are being used more and more in retail applications to highlight and emphasize products.


Incandescent lamps are the least efficient of all the major light sources. Tungsten halogen lamps are slightly more efficient than the standard incandescent lamps but still less efficient than the other sources.

For many of the popular lamp types there are energy efficient replacements designed to deliver approximately the same amount of light at reduced wattage. These lamps are generally more expensive than their corresponding standard lamps but the additional cost can be recovered in a few months worth of energy savings.


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