Compact Fluorescent Light FAQs
How do CFL bulbs work?CFL bulbs work like full-size fluorescent tubes. Mercury vapor in the bulb, excited by an electrical current, emits ultraviolet (UV) light. The UV light strikes the phosphor coating on the wall of the bulb and gives off visible light. The type of phosphor determines the color temperature and color rendition of the light. The current through the bulb is regulated by an electronic device called a "ballast". The ballast is built into the base of most screw-in CFL bulbs. What does the ENERGY STAR® label mean on a CFL bulb?ENERGY STAR is a U.S. government-backed program to help protect the environment through superior energy efficiency. ENERGY STAR labels make it easier for consumers to locate energy-efficient lighting, appliances, electronic products and more. ENERGY STAR qualified CFL bulbs must meet a variety of standards that help assure consumer satisfaction. Learn more... ENERGY STAR qualified CFL bulbs must meet standards in these areas:
As technology improves, the standards are periodically updated. Are there bulb styles that aren't ENERGY STAR qualified?At this time, ENERGY STAR does not have standards for candelabra-base bulbs. Do CFL bulbs flicker and hum?Today's ENERGY STAR qualified CFL bulbs turn on almost instantly, are quiet and don't flicker. I tried CFL bulbs a few years ago and didn't like them. What's changed?Early CFL bulbs were expensive and many people didn't like their performance. Today's ENERGY STAR qualified CFL bulbs:
Today's ENERGY STAR qualified CFL bulbs are a whole new generation of technology that have eliminated complaints common with older products. They cost much less while offering great performance. You can now buy CFL bulbs with as much light output as you want. They turn on almost instantly, are quiet and don't flicker. Light quality is excellent. CFL bulbs come in a wide variety of shapes. They are comparable in size, sometimes smaller, than the incandescent bulbs they replace. They also last much longer than standard bulbs. Why does it take time for CFL bulbs to come up to full brightness?It takes a little time for the mercury in CFL bulbs to vaporize and reach operating temperature. Some bulbs reach full brightness in a few seconds, while others can take as much as a minute. Learn more... Most CFL bulbs reach full brightness very quickly, but some take as much as a minute. The slower warm-up is due to an additive called "amalgam." It's used in bulbs that operate in a wide temperature range, such as reflector flood bulbs operating in recessed lighting or some bulbs specifically designed for use outdoors. The benefit of bulbs that use amalgam is that they produce full-light output over the range of temperatures-the disadvantage is slower warm-up. CFL bulbs without amalgam, operating in cold locations such as outdoors or in a garage, also take longer to reach full brightness. They may initially come on quite dim but will brighten as they self-heat. How long do CFL bulbs last?All ENERGY STAR qualified CFL bulbs have a rated life of at least 6,000 hours. For a light that's on three hours a day, that's more than five years. Many CFL bulbs have rated lifetimes of 8,000 to 12,000 hours. compared to a standard bulb with a 1,000-hour rated lifetime, you seldom have to change CFL bulbs. Learn more...For any type of light bulb, the rated life is defined as the time when half of the tested samples are still burning. One bulb rated at 8,000 hours may burn out at 5,300 hours, while another may last for 12,000 hours or more. Some manufacturers make guarantees about how long their products will last.
Does the light produced by CFL bulbs look like the light I'm used to?
Most ENERGY STAR® qualified CFL bulbs produce light that is a good match to standard bulbs. Some manufacturers label these bulbs "Soft White". Light from bulbs labeled "Cool White", "Bright White" or "Daylight" will be whiter and/or bluer than the light from standard bulbs, but these choices are preferred by some people. Color temperature and Color Rendering Index (CRI) ratings help you select appropriate products. What is "color temperature"?Color temperature is a rating that distinguishes whether a CFL bulb puts out light that has a yellowish tinge (like standard lighting) or light with a whiter or bluer tinge (such as a "cool white" or "daylight" bulb that some prefer). ENERGY STAR qualified products that don't specify a color temperature will be a good match with standard lighting. Learn more...
"Correlated Color Temperature" (CCT) is an important measure of the color of light produced. The CCT value is available for all light bulbs and helps you choose the appropriate bulb.
CCT is measured in degrees Kelvin (K). Imagine a piece of metal being heated. As its temperature increases, the color of the metal will gradually shift from red to orange to yellow to white to bluish white. This table lists the typical color temperature of various light sources.
What is "Color Rendering Index"?The "Color Rendering Index"(CRI) describes how colored objects appear under a given light source. Early fluorescent lighting products rendered colors poorly. In contrast, to today's ENERGY STAR qualified lighting that performs well. Learn more... The CRI rating is available for all light bulbs and helps you choose the appropriate bulb. CRI is measured on a 100-point scale, with 100 being a reference value of a particular incandescent light. A low CRI indicates that objects may appear unnatural under the source, while a light with a high CRI rating allows an object's colors to appear more natural. Lights with CRI values of 80 or higher are considered to do a good job of rendering colors. Most CFL bulbs available locally have CRI ratings of 82 to 84, considered excellent values. CFL bulbs with CRI values in the high 80s can be found through other sources. Color temperature is another important specification for the light quality of a CFL ulb. Where can I buy CFL bulbs?CFL bulbs can be purchased at lighting stores, hardware and home improvement stores, drug stores, grocery stores, mass merchants and wholesale clubs. Businesses can buy CFL bulbs through electric wholesale suppliers as well. An Internet search will turn up many CFL suppliers who ship products. How do I know which CFL bulb to buy?When possible, buy an ENERGY STAR® labeled bulb. Also pay attention to the light output, wattage and color. CFL bulb labels are sometimes confusing, but finding the bulb that will give you the appropriate brightness is easy. One approach is to divide the wattage of the standard bulb you're replacing by 3.5. For instance, replace a 100 Watt standard bulb with a 25 to 30 Watt CFL bulb. The table below can help you select the right CFL bulb. First, find the bulb with the light output you need, then choose the one with the lowest power consumption. Light output (lumens) and power consumption (watts) are listed on all ENERGY STAR qualified CFL packages. The table provides a rough guide for bulb selection. The wattage needed depends on whether the CFL is exposed (bare spiral bulbs) or enclosed (globe or capsule bulbs).
How much of my electric use goes to lighting?Typically 10-20% of your total electric usage goes to lighting. The portion is higher during the winter because nights are longer and you are indoors more. How much energy and money do CFL bulbs save?Even though a CFL bulb is more expensive than a standard bulb, the savings far exceed the purchase price. A $5 CFL bulb will often save you $25 to $30 over its life. The more fixtures you convert to CFL bulbs, the more you'll save. Learn more...The energy savings depend on the wattages and lifetimes of the CFL bulb and the standard bulb it replaces and the electric rate. The savings related to bulb replacement depend on the costs of the CFL and standard bulb and their rated lifetimes. An example: You replace a 75-Watt standard bulb, costing 50 cents, with a 1,000-hour rated lifetime, with a 20-Watt CFL bulb rated at 8,000 hours, selling for $5. Over the lifetime of the CFL bulb:
Your total savings for this example is $28.60 (energy savings) + $4 (bulb replacement savings) - $5 (CFL bulb price) = $27.60. You'll spend $5 and get your investment back more than five times over. How much do CFL bulbs cost?The least expensive are the bare, spiral-shaped models. Single bulbs are generally priced from about $5-8. In multi-packs, the per-bulb prices generally are from $1.75-4. Prices for other styles, including globes, "A-lamp," and reflector bulbs, are higher; expect to pay $4-12 per bulb. Multi-packs have lower per-bulb pricing than single bulbs. Prices for specialty products, including three-way and dimmable CFLs, range from $10-15. Even with higher purchase prices, CFL bulbs are smart buys because of the energy and money savings they deliver. Should I wait to replace my standard bulbs until they burn out?No. Though it's tempting to want to 'get your money's worth' out of the light bulbs you've already purchased, it's still a better deal to change to CFLs. A 75-Watt standard bulb burning 3 hours per day costs about 45 cents per month in electricity (meaning the monthly cost to operate the bulb is about equal to the purchase price). A 20-Watt CFL replacement will cost you about 12 cents a month to operate. The difference adds up quickly. Start saving 33 cents a month—or about $4 a year—for every light bulb you switch out today. What are the best locations for CFL bulbs?Start with fixtures that are:
Are there any locations where CFL bulbs are NOT recommended?CFL bulbs are not the best choice for:
Fixtures in which heat can build up, such as recessed lighting or tightly enclosed fixtures, may need some special attention. Can CFL bulbs be used in recessed can-style light fixtures?Yes. For more light output and cooler operation, only reflector style (R-lamp) bulbs should be used in recessed can fixtures. Learn more... Challenges in converting recessed lighting fixtures to CFL bulbs, include:
Despite these challenges, many people successfully use CFL bulbs in recessed fixtures. Is it OK to use CFL bulbs in enclosed fixtures?Bulbs operating in enclosed fixtures must perform well at higher temperatures. Underwriter's Lab (UL) tests products for use in that application. If an ENERGY STAR qualified product does not pass the UL test, it must be labeled, "Not for use in totally enclosed fixtures." Otherwise, no label is required. Always read the information on the package. Do CFL bulbs work in three-way light sockets?Yes, but a regular CFL will not light in the first (low-light level) switch position and will only give one level of light in the other two switch positions. To have three choices of light levels, you'll need to buy a three-way CFL bulb. Can CFL bulbs be controlled with dimmers?Don't use regular CFL bulbs in sockets controlled by conventional dimmer controls. Specially designed CFL bulbs will work in these locations with dimmability specified on the packaging. Some people have not been satisfied with the light quality when they're dimmed. You can purchase CFL lighting fixtures with built-in dimming ballasts and plug-in (rather than screw-in) bulbs, along with dimming controls specially designed to match. Do CFL bulbs work with timers?CFL bulbs may not work with certain electronic timers. They will work fine with a mechanical timer switch. Always read the information on the package. Do CFL bulbs work with photo-sensors?CFL bulbs may not work with certain photo-sensor controls. Always read the information on the package. CFL lighting fixtures with built-in controls are available. Do CFL bulbs work outdoors?CFL bulbs generally work acceptably outdoors. They should always be protected against rain and snow. Learn more...Many of today's CFLs will start at temperatures as low as zero degrees Fahrenheit and some at 20 degrees below zero (read the packaging). CFL performance is temperature sensitive, and light output is greatest at typical room temperatures and falls off at low and high temperatures. CFLs used outdoors in cold temperatures will take longer to reach brightness and won't produce as much light as when used indoors. When used in an enclosed fixture, the bulb's heat warms the fixture, and the light output is generally acceptable even when it's quite cold. Do CFL bulbs perform well in humid environments like bathrooms?Generally, yes, but anecdotal evidence suggests that some CFL bulbs may not last as long. If the bulb fails early, contact the manufacturer. Is it a good idea to turn CFL bulbs off when I leave the room?Yes. Turning off lights always saves energy. It is a common belief that fluorescent lights require a big, expensive surge of electricity to start. Any such power spike lasts milliseconds at most, with no appreciable energy use or cost. Turning a CFL bulb on and off very frequently though (e.g., flipping the switch up and down), will shorten its life. A good rule-of-thumb might be to turn off the lights whenever you leave the room for five minutes or more. How do CFL bulbs fail?A CFL bulb will occasionally burn out. More often, it will continue to operate, gradually producing less light as it ages. At some point you'll want to replace it for brighter light. Note that an ENERGY STAR qualified CFL bulb must produce at least 80 percent of its rated light output at 40 percent of its rated life. What should I do if my CFL bulb fails early?Contact the manufacturer, who is ultimately responsible for warranty claims. Be sure to save the proof-of-purchase and register receipt to document your claim. How should I dispose of old CFL bulbs?CFL Disposal Brochure (PDF 395KB) All fluorescent bulbs, including CFLs, contain small amounts of mercury, an environmental concern. Mercury is a toxic metal associated with contamination of water, fish and food supplies. While it is legal for residential CFL users to throw them in the trash, Fort Collins Utilities encourages they be recycled. Unbroken CFLs can be recycled at:
Broken and unbroken CFLs can be recycled at several local retailers, including:
Learn more about this comprehensive recycling program, sponsored by Platte River Power Authority, at www.mercurytechnologies-mn.com. In-depth information regarding overall disposal of fluorescent bulbs can be found at www.lamprecycle.org. When recycling at any of the locations, please ensure all bulbs are sealed in a plastic bag. LED Holiday LightingHow much energy and money do LED holiday lights save?
The key assumptions are: five strings operating five hours per day for one month per season, for five seasons. Fort Collins Utilities Residential Electric Rate. LED holiday lights save a lot of energy compared with traditional incandescent lighting. The graph on the right shows how much you could reduce your electrical bill by changing from different types of incandescent strings to LED holiday strings. What types of LED holiday light products are available?Mini-ice, ball-shaped, C-7, C-9, icicle lights and more in a variety of colors. Where can I buy LED holiday lighting?Various Fort Collins hardware and department stores carry LED lights. Learn about local retailers participating in this year’s holiday lighting exchange. An Internet search will turn up other mail-order sources. How long will LED light strings last?The bulbs are rated to last tens of thousands of hours. The wiring is liable to be the weak link. Treat the strings with care (don’t use staples to hang light strings, wrap the wires around nails or overexpose light sets to sunlight). Are there any cautions about buying LED holiday light products?Some LED holiday lighting products exhibit a flicker that a few people notice, especially in their peripheral vision. Others have no flicker. Ideally you will have a chance to see the product operate before you purchase. The main color issue has to do with “white” LED bulbs. Most people are used to “white” incandescent bulbs that are on the warm side of white, with a yellow tinge. Many white LED bulbs are on the cool side of white, with a blue tinge. Again, try to see the product in operation before you make your purchase. |
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