Compact Fluorescent LampsCompact fluorescent lamps (CFLs) are smaller versions of standard fluorescent lamps. They consume between 5 to 40 watts, and have a brightness and color rendition that is comparable to incandescent lights. Unlike standard fluorescent lamps, they can directly replace standard incandescent bulbs. CFLs work much like standard fluorescent lamps. They consist of two parts, a gas-filled tube and a magnetic or electronic ballast. The gas in the tube glows with ultraviolet light when electricity from the ballast flows through it. This in turn excites a white phosphor coating on the inside of the tube, which emits visible light throughout the surface of the tube. Incandescent lamps work differently. Most of the electricity they use heats a tungsten filament until it glows white hot. As a result, incandescent lamps generate far more heat than a fluorescent light. Since the light source is a single point, incandescents also project light further than CFLs that project a more diffuse light. You should consider this when replacing incandescents with CFL’s in high ceiling applications. CFLs are available in a variety of styles or shapes. Some have two, four, or six tubes, while some have a circular tube. New versions have a spiral-shaped tube. The size or total surface area of the tube(s) determines how much light it produces. Some CFLs have the tubes and ballast permanently connected. Other CFLs have separate tubes and ballasts. This allows you to change the tubes without changing the ballast. There are also types that are encapsulated in a glass globe. These look somewhat similar to conventional incandescent light bulbs. CFLs with magnetic ballasts flicker slightly when they start. They are also heavier than electronic ballasts. This may make them too heavy for some light fixtures. Electronic ballasts are more expensive, but light immediately (especially at low temperatures), and are more efficient than magnetic ballasts. The tubes will last about 10,000 hours and the ballast about 50,000 hours. CFLs have the following advantages over incandescent light bulbs when used properly: they last up to 10 times longer, use about 1/4 the energy, and produce 90% less heat, while producing more light per watt. For example, a 27 watt compact fluorescent lamp provides about 1800 lumens, compared to 1750 lumens from a 100 watt incandescent lamp. The following is a comparison between the wattage of commonly available incandescent lamps and the wattage of a CFL that will provide similar light levels: 25 Watt Incandescent = 5 Watt CFL50 = 9 60 = 15 75 = 20 100 = 25 120 = 28 150 = 39
A major advantage of using CFLs, however, is to save money, as shown in the table below. This table assumes the light is on for 6 hours per day and that the electric rate is 10 cents per kilowatt-hour.
CFLs are most cost effective and efficient in areas where lights are on for long periods of time. You may see a slower payback in areas where the light is turned on and off often, or where they are on for only a few minutes, such as closets and pantries. Because CFLs do not need to be changed often, they are ideal for hard-to-reach areas. CFLs that work with dimming switches are now available. Most, however, cannot be dimmed. You should check with the manufacturer for dimming applications. Although most CFLs fit into an existing 3-way light socket, only a few special models can light to more than one level. A new type of CFL- Cold Cathode Fluorescent Light (CCFL) - has been developed. CCFL's bulbs even more efficient, produce less heat, and are smaller and more compact. They are also projected to last much longer than conventional CFL's bulbs and ballasts. CCFL's may be available for sale in the near future. CFLs are designed to operate within a specific temperature range. Temperatures below the range cause reduced output. Most are for indoor use, but there are models available for outdoor use. You can find a CFL’s temperature range on most lamp packages. You should install outdoor CFLs in enclosed fixtures to minimize the adverse effects of colder temperatures. In addition to their higher initial cost, CFLs are usually physically larger than incandescent lamps. This may make them difficult to use in some light fixtures. However, smaller models are now becoming available. These "Sub-CFLs" are a new generation of smaller compact fluorescent lamps that fit most fixtures designed for incandescent lamps. Since incandescent bulbs project light further than CFLs, which project a more diffuse light, you should consider this when replacing incandescents with CFL's in high ceiling applications. Fluorescent tubes also contain a microscopic amount of mercury. While it is such a small amount that disposal is not usually regulated (as with full size fluorescent lamps), you should use caution to avoid crushing the tubes, and dispose of them safely. To purchase CFLs, try home and building supply centers, hardware stores, and specialty lighting retailers. If the salesperson is not aware of the product you want to purchase, speak to the manager of the store. The manager may be able to special order the bulb from the representative who supplies lighting products to the store. There are also many mail order firms that distribute energy-efficient and renewable energy products. Also, your local electric utility may offer rebates or other incentives for CFL's. BibliographyFor further information on energy-efficient light bulbs, you may wish to obtain the following publications. This bibliography was reviewed in November 2002. "Bright Prospects for CFL Torchieres," C. Calwell, Home Energy, (14:1) p. 13, January/February 1997. "CCFL May Spur a Revolution in Efficient Lighting," Ed., Energy Design Update, p. 12, June 2001. "Changing Attitudes on Changing Lamps," E. Page, Home Energy, (15:3) p. 29-32, May/June 1998. Consumer Guide to Home Energy Savings, 7th Ed., A. Wilson, J. Morrill, and J. Thorne, pp. 230, American Council for an Energy-Efficient Economy (ACEEE), 2000. Available from ACEEE, 1001 Connecticut Avenue, NW, Suite 801, Washington, DC 20036; Phone: (202) 429-0063; World Wide Web: www.aceee.org . $8.95. "Dedicated Fixtures for Compact Fluorescents," T. Maker, The Journal of Light Construction, (12:4) p. 52, January 1994. "Energy-Efficient Lighting for the Home," J. Byrne, Home Energy, (11:6) pp. 53-60, November/December 1994. "Light Bulbs with a Very, Very Long Life," Consumer Reports, (59:8) p. 492, August 1994. "Second Generation CFL Torchieres On the Way," Ed., Environmental Building News, (7:9) pp. 5-6, October 1998. "Screw-In Dimmable Compact Fluorescent," J. Nisson (ed.), Energy Design Update, (17:4) pp. 13-13, April 1997. "Shedding Light on Home Lighting Use," L. Tribwell, Home Energy, (14:1) pp. 15-19, January/February 1997.
This brief was reviewed for accuracy and updated in November 2002. EREC is operated by NCI Information Systems, Inc. for the National Renewable Energy Laboratory/U.S. Department of Energy. The content of this brief is based on information known to EREC at the time of preparation. No recommendation or endorsement of any non-US Government product or service is implied if mentioned by EREC. Your interest in energy efficiency and renewable energy is greatly appreciated. If we can be of further assistance, please feel free to contact us again. Ask an
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