CFL Facts and Myths
There is increasing interest in replacing incandescent lamps with compact fluorescent lamps (CFLs) as one means of reducing energy consumption and the generation of greenhouse gasses that contribute to global warming. One example of this is that legislators in both California and Australia have proposed bills that would ban the use of incandescent lamps.
On the flip side, consumers have raised a number of questions and concerns regarding the operation, use, and safety of CFLs. These range from the perception of poor color, concerns about flickering, questions about the life of CFLs when they are turned on and off frequently, questions about the performance of CFLs used outdoors in cold weather and concerns about the mercury used in fluorescent lamps and their proper disposal.
The goal of this site is to provide answers to a wide range of questions about CFLs in a Question & Answer format. The site does not recommend or discuss specific products or manufacturers. Most of the information provided should be useful to consumers and other CFL users in any country, though some answers may be specific to users in the United States. A link at the bottom of the page can be used by readers to provide feedback and we will use that feedback to improve and update the Q&A. That same link can be used to ask questions, which will be individually answered as time permits.
- What is a CFL?
- CFL stands for Compact Fluorescent Lamp. A compact fluorescent lamp is a smaller version of the fluorescent lamps that have been used to provide energy-efficient light for offices, factories, stores and schools for over 60 years.
- Why are CFLs called lamps instead of bulbs?
- In lamp-industry jargon, a lamp is a device that generates light when connected to electric power. The term bulb is used to describe the glassware before it is made into a functional lamp. In addition, the device that most users would call a lamp, is called a fixture or luminaire in the lighting industry. For example, what most people refer to as a table lamp is technically called a portable fixture. Aren't you glad you asked?
- Why do CFLs look so strange?
- Most fluorescent lamps are constructed in long, thin tubes in order to generate light while using the least amount of electricity. In order to fit CFLs into a lighting fixture designed for incandescent lamps, the long, thin tube must be coiled into a spiral or folded back on itself multiple times. This accounts for the unusual shape of most CFLs.
- Is it possible to make a CFL that looks like a normal incandescent lamp?
- Yes. One way is to enclose the spiral or folded tube in a glass or plastic outer housing. A better way is to make an electrodeless CFL using what is called induction coupling. Electrodeless CFLs can be constructed in bulbs that have the same shape as conventional incandescent lamps. Only three models of electrodeless CFLs are currently sold in the U.S. Two of these electrodeless CFLs are constructed as reflector lamps. The third electrodeless CFL looks very much like a conventional incandescent lamp, also known as an A-Line lamp.
- Why does my CFL make me look like a cadaver?
- While even the best CFLs may not make people and objects look exactly the same as they do with an incandescent lamp, some CFLs make many people look terrible and cause them to reject CFLs in their homes. In most cases, this problem is easily solved.
CFLs, like all fluorescent lamps, are sold in various colors, and some of these will render skin colors very poorly. It's hard to avoid a bit of technical jargon when discussing the color quality of light sources, so I'll need to use some jargon here. The color of a lamp is specified using the term Correlated Color Temperature, which is the temperature of a blackbody, in Kelvin, that has a color that is the best match to the color of the lamp. (The Kelvin is a unit of temperature based on absolute zero. 273.15 Kelvin is equal to 0 degrees Celsius.)
Candles have a Correlated Color Temperature of about 1700K. Typical incandescent lamps used in homes have Correlated Color Temperatures that range from about 2700K to 2900K. Those small halogen incandescent lamps used for desk lamps have Correlated Color Temperatures close to 3000K. The sun has a Correlated Color Temperature of about 5800K, while blue sky has a Correlated Color Temperature of about 6500K. So, you can see that as the Correlated Color Temperature increases, the color of the light source moves from reddish to bluish.
Now, the problem. CFLs are made with Correlated Color Temperatures ranging from 2700K (like an incandescent lamp) to 6000K, bluer than the sun; but it is hard for the average consumer to know what Correlated Color Temperature lamp they are buying. Some manufacturers use made-up names like natural white or soft white instead of the actual Correlated Color Temperature. Other manufacturers print the Correlated Color Temperature on the box or the base of the lamp in small numbers such as 3000K, but with no explanation of what these numbers mean. I don't know of any CFLs sold to the general public that list the Correlated Color Temperature in an easy to find place and explain what the number means.
The good news is that proposed ENERGY STAR® Program Requirements for CFLs, not yet issued as of January 29, 2009, will require CFLs to have the Correlated Color Temperature printed on the packaging in order to be ENERGY STAR qualified.
I urge those people who have found the color of CFLs to be totally unacceptable to check the color temperature of the lamps they bought. If your CFLs are not 2700K or 3000K, then I suggest you buy some 2700K or 3000K lamps and give them another chance.
- While even the best CFLs may not make people and objects look exactly the same as they do with an incandescent lamp, some CFLs make many people look terrible and cause them to reject CFLs in their homes. In most cases, this problem is easily solved.
- What are screw-base CFLs and how do they differ from pin-base CFLs?
- Most CFLs used in homes have an Edison screw base on the bottom. These are commonly known as screw-base CFLs. The special power supply used to operate the CFL, called a "ballast" in the United States, is enclosed in the plastic shell of the CFL located between the glass part that creates the light and the Edison screw base. Screw-base CFLs are also called self-ballasted CFLs because the ballast is integrated into the lamp as a non-removable part. Pin-base CFLs have small plastic bases with 2 or 4 pins that each have a diameter of about 0.1 inches. The base does not contain a ballast. Pin-base CFLs are designed to be used with separate ballasts that are mounted in special fixtures designed for pin-base CFLs. Pin-base CFLs and their special fixtures are found mostly in commercial buildings such as office buildings, stores and schools. Pin-base CFLs should not be confused with a new type of CFL, described below, that uses the GU24 base.
- What is a GU24 base and how is it related to CFLs?
- The GU24 socket and base system is designed to replace the Edison socket and base in energy efficient lighting fixtures. The ENERGY STAR® Program Requirements for Residential Lighting Fixtures, Version 4.0 require that residential lighting fixtures cannot use the standard Edison screw base, even if they do not have a built-in ballast. The same requirement is included in California's Energy Efficiency Standards for Residential and Nonresidential Buildings, known as Title 24-2005. This requirement is designed to insure that fixtures that receive ENERGY STAR® qualification when using an energy-efficient self-ballasted CFL, or are qualified as energy-efficient under Title 24-2005 cannot be operated with an incandescent lamp. The GU24 socket was designed to be compatible with these energy efficiency regulations. The GU24 base has two dual-diameter pins; the smaller portion having a diameter of 3.4 mm (0.13 inches) while the larger portion has a diameter of 5 mm (0.2 inches). [A link to a drawing of a GU24 base will be added.] CFLs with a GU24 base are designed to be connected directly to the power line, so they are functionally equivalent to screw-base CFLs instead of normal pin-base CFLs. Unfortunately, ENERGY STAR® refers to CFLs with the GU24 base as self-ballasted pin base lamps, a designation that may lead to confusion with pin-base CFLs that do not have an integral ballast. Some manufacturers are also making modular ballasts with a GU24 base on one end and a socket for a normal pin-base CFL on the other. These modular ballasts can be used to adapt normal pin-base CFLs to fixtures that have the GU24 socket, thereby reducing the amount of material that must be thrown away when the lamp fails.
- Do CFLs work on dimmers?
- Most screw-base CFLs do not work with dimmers designed for use with incandescent lamps. These CFLs will have a label on the lamp and/or the packaging stating "not for use with dimmers. However, certain special screw-base CFLs are designed to work with standard incandescent lamp dimmers. These CFLs will be labeled "dimmable" or similar language on the lamp and/or the packaging. However, due to small differences between different brands of dimmers, not all dimmable CFLs work with all types of incandescent dimmers. Some dimmable CFLs, however, will work with all major brands of incandescent lamp dimmers.
- I have read that CFLs contain mercury. Is that correct?
- Yes, all CFLs contain a very small amount of mercury, typically about 5 mg, which is 1/6000th of an ounce (mass). If all the mercury were concentrated in one droplet, that droplet would have a diameter of only 1.1 mm, which is 0.042 inches. Typical mercury-based fever thermometers contain 0.5 to 3 grams of mercury, which is 100 to 600 times as much mercury as a CFL that has 5 mg of mercury. Data on the mercury content of fever thermometers comes from: Mercury and the Environment - Sources of Mercury - Mercury Containing Products, a web site maintained by the Canadian government.
- Doesn't disposal of mercury-based products harm the environment?
- Yes, mercury is classified as a hazardous material by the US Environmental Protection Agency and CFLs should be recycled instead of being thrown out with the normal trash. However, in many cases use of CFLs will offset mercury that would otherwise be introduced into the environment from other sources. For example, coal contains mercury and this mercury is released into the environment when coal is burned to produce electricity. If the electricity used to operate your lamps is generated from coal, and you operate 100-watt incandescent lamps for 10,000 hours, the power generating plant will release between 40 mg and 70 mg of mercury into the environment, depending upon the type of coal being used. If instead of the 100-watt incandescent lamp, you use a 25-watt CFL, the power plant mercury emissions drop to between 10 and 18 mg over the same 10,000 hour period, again depending upon the type of coal used. Even when the 5 mg of mercury in the CFL is added to the environment at the end of the lamp's 10,000 hours life, the total mercury from using the CFL is far less than using the incandescent lamp. Mercury emissions will be lower for For lower power incandescent lamps and CFL replacements, but for any incandescent lamp of 40 watts or greater, there will be more mercury added to the environment by using an incandescent lamp than by using a CFL, assuming that the electricity used to operate both is generated by burning coal.
If the electrical power used to operate your lamps comes from oil, hydro, wind, even nuclear power plants then use of a CFL will not be directly offsetting mercury released by power plants. However, by using less electrical power from your "low-mercury" or "mercury-free" generating plant, you make more of this relatively clean power available to replace power generated by coal-fired plants. And, you will save money, no matter what type of fuel is used to generate your electrical power.
Because CFLs contain mercury they should be recycled instead of thrown in the normal trash. However, even if a relatively large number of CFLs are disposed of in landfills instead of being recycled, they will not significantly increase the amount of mercury in the waste stream. A report titled Mercury Programme, published by the United Nations Environmental Programme, estimated that in 2000 there were 145 metric tons of mercury added to the solid waste stream in the United States. If 200 million CFLs, each containing 5 mg of mercury were placed in the solid waste stream in one year, they would add only 1 metric ton, or less than 0.7% of the total annual mercury load in the waste stream.
- Yes, mercury is classified as a hazardous material by the US Environmental Protection Agency and CFLs should be recycled instead of being thrown out with the normal trash. However, in many cases use of CFLs will offset mercury that would otherwise be introduced into the environment from other sources. For example, coal contains mercury and this mercury is released into the environment when coal is burned to produce electricity. If the electricity used to operate your lamps is generated from coal, and you operate 100-watt incandescent lamps for 10,000 hours, the power generating plant will release between 40 mg and 70 mg of mercury into the environment, depending upon the type of coal being used. If instead of the 100-watt incandescent lamp, you use a 25-watt CFL, the power plant mercury emissions drop to between 10 and 18 mg over the same 10,000 hour period, again depending upon the type of coal used. Even when the 5 mg of mercury in the CFL is added to the environment at the end of the lamp's 10,000 hours life, the total mercury from using the CFL is far less than using the incandescent lamp. Mercury emissions will be lower for For lower power incandescent lamps and CFL replacements, but for any incandescent lamp of 40 watts or greater, there will be more mercury added to the environment by using an incandescent lamp than by using a CFL, assuming that the electricity used to operate both is generated by burning coal.
- What should I do if I break a CFL?
- ENERGY STAR® has created a fact sheet that provides recommendations for cleaning up a broken fluorescent lamp. These recommendations will be updated periodically by ENERGY STAR®, but the link provided should always point to the most recent version.
- Do 2-pin CFLs work on dimmers?
- First, I need to make it clear that in this item I am discussing plug-in CFLs that have two straight pins and use separate ballasts. CFLs with GU24 bases, that have two dual-diameter pins, and that Energy Star has unfortunately decided to call pin-base CFLs, are not the same as 2-pin CFLs. CFLs with GU24 bases have an internal ballast, and some of these are dimmable. Normal 2-pin CFLs have a glow switch (starter) installed in the plastic protrusion between the two pins and cannot be dimmed.