I9 Compact Fluorescent Lamps



Compact fluorescent lamps are small-size fluorescent lamps. They need a ballast to operate, as do all fluorescent lamps. The ballast supplies the right voltage to start and operate the lamp. A ballast is a device used with a gas discharge lamp to provide the necessary starting and operating electrical conditions.

They use an electrical discharge in a mixture of rare gas and mercury vapor to create ultraviolet (UV) photons, which cause a phosphor coating on the inside of glass tubes to emit visible light These same phosphors give CFLs high efficacy and good color rendering.

CFLs from the major manufacturers are now available with power ratings that range from 5 to to 120 watts


The CFL family is composed of two general types of lamps:

  • Self-Ballasted CFLs Also known as screw-base, screw-in, or integrally ballasted CFLs, self-ballasted CFLs are designed to replace incandescent lamps without requiring any modifications to the existing incandescent lamp fixtures. Self-ballasted or screw based lamps, for direct replacement of incandescent lamps
  • Pin-Base CFLs Also known as plug-in CFLs, these are designed to be used with a separate ballast. Four-pin CFLs do not contain glow starters. They are most often used with magnetic or electronic rapid-start or programmed rapidstart ballasts. Pin-based lamps for compact fluorescent light fixtures hardwired systems, dedicated systems consist of a ballast and socket for a pin-base CFL that are permanently wired into a fixture by the fixture manufacturer or as part of a retrofit kit.
  • They are also available in a large variety of sizes and wattages, and in twin-tube, quad-tube, long tube, twisted, reflectorized and fully enclosed versions.
  • Self-ballasted CFLs are available with permanent or removable reflectors or A-line-, globe-, or cylinder-shaped translucent covers.


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  • Self-ballasted CFLs have decreased in size so that many are now as small as the incandescent lamps they are designed to replace, which means they will fit into a greater variety of incandescent lamp fixtures.
  • Electronic ballasts have replaced magnetic ballasts in virtually all self-ballasted CFLs.
  • Efficacy or lamp efficiency increases with lamp size and wattage. The smaller size, lower wattage lamps are generally less efficient than the larger size and higher wattage lamps.
  • The efficacy (lumens per watt) of CFLs varies considerably with lamp wattage and ballast type and quality. The efficacy of a 5-watt lamp on a low-quality magnetic ballast, for example, can be as low as 27 lumens per watt (lm/W). At the other extreme, two 36-watt CFLs powered by a single high-quality electronic ballast deliver nearly 77 lm/W.
  • Compact fluorescent lamps are about four times more efficient than standard incandescent lamps.
  • Compact fluorescents have an average life that is 10 times longer than that of standard incandescent lamps, and have a lower maintenance costs. Most low-power CFLs have rated lives of about 10,000 hours, The life of CFLs can be dramatically reduced by frequent cycling, or it can be extended beyond their rated life by continuous operation. CFL lifetimes range from 6,000 to 20,000 hours at 3 hours per start, but lifetimes can be considerably shorter with more frequent cycling.
  • They have a high colour rendering index, generally >82, but lower than incandescent lamps.
  • Most compact fluorescent lamps are available with a variety of colour temperature values, (3,000 K, 3,500 K, 4,100 K). available in four color temperatures: 2,700 kelvins (K), which is similar to the warm tone of standard incandescent lamps; 3,000 K; 3,500 K; and 4,100 K. Models with color temperatures of 5,000 and 6,500 K are available in certain sizes. Because CFLs often replace incandescent lamps with color temperatures around 2,700 K, CFL color choice is important when trying to maintain an existing ambience. Most self-ballasted CFLs, which are used as direct replacements for incandescent lamps, are available only at 2,700 K. Studies indicate that at lower light levels, warmer colors
  • As CFLs age, their light output diminishes more than that of incandescent lamps.
  • CFLs’ light output is sensitive to temperature, mounting position, and other factors.
  • CFLs take a longer time than incandescent lamps to produce full output after being turned on.


One of the conspicuous drawbacks of CFL technology has been the lack of cost-effective dimming options for pin-base lamps. The main reason for the lack of hardwired dimming ballasts for pin-base CFLs is not technical but economic. High-quality hardwired dimming ballasts are available for pin-base CFL lamps he problem is that these dimming ballasts cost two to three times as much as equivalent nondimming ballasts. Dimmable self-ballasted CFLs that operate on phase control dimmers for standard incandescent lamps have become available in recent years, as have other models that operate in standard three-way incandescent sockets.

Energy Star Program

There is an Energy Star program for compact fluorescent lamps in North America. In 1999 CFLs were incorporated into the Energy Star program Key Energy Star requirements for self-ballasted, screw-base CFLs including: minimum efficacy, color quality, lumen maintenance, power factor, starting time, lamp life


There is also an Energy Star program for residential compact fluorescent fixtures.

  • Many manufacturers produce fixtures for compact fluorescent lamps which include a specially designed ballast and socket (lamp holder). These are available in recessed, outdoor and decorative versions.
  • Lamp manufacturers produce retrofit adapters which include the ballast and lamp socket, and have a base to screw directly into a standard incandescent socket (see Self-Ballasted Types, above.).
  • Recessed compact fluorescent fixtures should have a properly designed reflector, otherwise light will be trapped inside the fixtures and be wasted.
  • The best CFL is worthless if installed in a poor fixture. As discussed earlier, CFL performance is highly sensitive to temperature and orientation—factors that are often determined by the fixture in which the CFL is installed. Home improvement centers like Home Depot and Lowe’s now carry dedicated outdoor CFL fixtures and replacement pin-based lamps, making the technology available to most residential and small commercial customers at affordable prices.
  • Fixtures equipped with high-efficacy CFLs are now available in just about every design that is typically used with incandescent lamps.

Most of these fixtures are available with high-performance electronic ballasts.


To replace light bulbs in fixtures which are not readily accessible. One of the most important yet underrated benefits of CFL technology is the dramatic reduction in relamping-associated labor costs it offers compared with incandescent lamps

  • Lobby areas, hallways and corridors,.
  • Recessed downlight fixtures.
  • Wall and ceiling-mounted fixtures.
  • Directional signs.
  • Security lighting fixtures.
  • Desk and task lighting fixtures.
  • Display lighting (museums, stores).