What is a compact fluorescent lamp?

April 17, 2015 10

A compact fluorescent lamp (CFL) is a type of fluorescent lamp. Many models of CFLs are available that are designed to replace traditional incandescent bulbs. The compact size of these CFLs allows them to fit into many existing incandescent light fixtures, including table and floor lamps.

There are two types of compact fluorescent lamps:

  1. Modular, with bulbs and ballasts that can be separated and replaced separately.
  2. Integral, with ballasts that are permanently built into the bulb and discarded with the bulb when the bulb burns out.

These types are being heavily promoted as energy savings alternatives to incandescent lamps. They also have a much longer life – usually 7500 to 10,000 hours, and sometimes up to 20,000 hours – compared to 750 to 1000 hours for a standard incandescent.

Incandescrent BulbsCFL bulbsStandard incandescent bulbs                   CFL Bulbs


When choosing to switch to CFLs, there are a few things to be aware of:

  • The elongated or circular shape may result in a less optimal lighting pattern.
  • CFLs usually do not produce full light output until they warm up for a minute or two. A few models require about three minutes to fully warm up and produce as little as 20-25 percent of their full light output when first started.
  • Many models have light output claims that are only achieved at the optimum operating temperature and/or in some optimum burning position that achieves an optimum internal temperature. Many light output claims are outright exaggerated, often by about 15 percent and in a few extreme cases by 25 percent.
  • The light is usually slightly different from that of incandescents, often slightly less yellow and slightly more pink, more purple, or more blue. The spectral output of these lamps is usually concentrated in a few specific bands of the spectrum, and this can slightly distort color rendering. Any color difference from other nearby lamps may be undesirable and result in less than pleasing contrast with ordinary lamps and ceiling fixtures. Newer models have been addressing this issue.
  • Some types (usually iron ballasts) may produce an annoying 120 Hz (or 100 Hz) flicker.
  • Ordinary dimmers cannot be used with CFLs
  • Like other fluorescents, operation at cold temperatures (under around 50 degrees F) may cause reduced light output or erratic operation. Some models work fairly well down to about 35 degrees F, others may get noticeably dim below 60 degrees F. The optimum temperature range of a particular lamp may vary with burning position, generally preferring cooler temperatures if operated base-down. CFLs may also not like excessive heat. Some ballasts are unreliable in ambient temperatures much over 120 degrees F. This is sometimes a problem in enclosed or recessed ceiling fixtures if heat in the fixture builds up.
  • There may be an audible buzz from the ballast, usually from iron ballasts.
  • They may produce Radio Frequency Interference (RFI).