Compact Fluorescent Light Bulbs
Compact fluorescent light bulbs, also known as CFLs, are an energy-efficient alternative to conventional incandescent bulbs.In an incandescent bulb, electric current heats a thin filament to the point that it glows. This design produces a warm, soft light, but the bulb loses most of its energy in the form of heat. In CFLs, electric current energizes argon and mercury vapor, which excites a glowing phosphor coating inside the bulb. This design loses very little energy to heat, which means it consumes much less power than an equivalent incandescent bulb.
CFL bulbs generally cost slightly more than incandescent bulbs, but they can pay for themselves in power bill savings. There is no industry standard for measuring energy efficiency, so energy savings ratings will vary from manufacturer to manufacturer. In general, a CFL will use around 75% less electricity than an incandescent light bulb with the same light output, while lasting about 10 times longer. Additionally, since CFLs produce less heat, they can help you save on cooling costs.
CFLs come in a range of shapes, sizes, color temperatures, and brightness levels, making it simple to replace most incandescent bulbs with an energy-efficient CFL alternative. While the first generation of CFLs had a characteristic blue tint, newer designs do a good job recreating the warm glow of incandescent bulbs. This buying guide will explain the available CFL options, so you can feel confident you’re selecting the light bulbs that will work best for you.
Factors to Consider
• Bulb Design – Bulb shape, base type, and lighting controls
• Light Output and Power Consumption – Watts, lumens, equivalent wattage, lumens per watt and bulb life
• Color – Soft white, bright white and daylight
• Safety and Recycling – Cleanup and disposal guidelines
Like incandescent bulbs, CFLs come in a variety of shapes, suited to different tasks and light fixtures. Common CFL bulb shapes include:
|Spiral Bulb – A basic CFL design with visible fluorescent tubes arranged in a spiral. Spiral bulbs, also known as twister bulbs, do an excellent job providing even light distribution and are ideal for lamps and light fixtures that hide the bulb behind a shade or covering.|
|A-Line Bulb – A bulb with a rounded cover that has the same basic appearance as a standard incandescent bulb. A-line bulbs are a good option if you have a light fixture that doesn’t conceal the bulb or a lamp with a shade that attaches directly to the bulb.|
|Globe Bulb – A sphere-shaped bulb, commonly used in bathroom light vanities and pendant lights|
|Indoor Reflector Bulb – A bulb that provides directional light. Indoor reflectors are used in recessed lighting, track lighting, and some ceiling fans.|
|Parabolic Aluminized Reflectors (PAR) – A durable bulb used for outdoor flood lights and spot lights.|
|Triple Tube Bulb – A compact bulb with visible fluorescent tubes. Triple tube bulbs have high light output but take up very little space, making them a good choice for reading lamps.|
|Post Bulb – A durable bulb designed for outdoor light fixtures.|
Bulb Base Type
As with incandescent bulbs, it’s essential when you’re shopping for CFLs to determine what bulb base size you need. If you’re going to the store, it’s a good idea to bring the bulb you’re replacing along with you, so you can match the base sizes. There are five standard base sizes for CFLs:
• Miniature Candelabra – A small bulb base, frequently used in chandeliers
• Candelabra – A slightly larger bulb base, used in chandeliers, light sconces and other small fixtures
• Intermediate – A bulb base between the candelabra and medium sizes, commonly used in ceiling fans
• Medium – The bulb base design for standard light bulbs, used in most lamps and overhead light fixtures
• GU24 – A two-pin base that fits fixtures with a corresponding GU24 socket. GU24 is an energy-efficient
system, designed to replace the conventional, screw-type socket and base design
Unlike standard incandescent bulbs, standard CFLs do not work with dimmer switches or 3-way lamps. However, you can find CFLs for these applications:
• Dimmable CFLs are designed to work with fixtures wired to a dimmer switch. A dimmable CFL cannot
produce the same range of light levels as an incandescent bulb connected to a dimmer, however.
Dimmable CFLs typically dim down to about 20% of total light output. Below that, the bulb switches off.
If you want to use a CFL with a dimmer switch, make sure you choose a bulb with “dimmable” on the
• Three-way CFLs are designed to work with three-way lamps. When you progress through the lamp’s
three lighting levels, the bulb steadily increases its light output.
Additionally, CFLs may not work with electronic lighting controls, such as timers and motion sensors. Check an electronic control’s product specifications to determine whether it’s designed for use with CFLs.
Light Output & Power Consumption
Like incandescent bulbs, CFLs are rated based on light output, which is closely related to power consumption. When selecting a bulb, consider these standard ratings:
• Watts – Bulb manufacturers have traditionally used watts to represent light output, but wattage is actually a
measure of power consumption, not brightness. Since CFLs consume less power, a CFL will have a much
lower wattage than an incandescent bulb that produces the same amount of light. In other words, a
lower wattage number indicates greater energy savings, not lower light output.
• Lumens – The standard unit of light output for bulbs is the lumen. A higher lumen number indicates a
brighter bulb, and a lower lumen number indicates a dimmer bulb. A CFL and an incandescent bulb with
the same lumen rating will produce the same amount of light
• Equivalent Wattage – To make it easier to compare CFLs to incandescent bulbs, manufacturers generally
provide an equivalent wattage rating for CFLs along with the lumens rating. The equivalent wattage tells
you what type of incandescent bulb has the same light output as the CFL. For example, a CFL with an
equivalent wattage of 60 produces the same amount of light as a 60-watt incandescent bulb.
• Lumens per watt – The standard measure of efficiency is the ratio of light output to power usage,
represented as lumens per watt, or LPW. A higher LPW rating indicates greater energy efficiency
and increased savings
• Bulb Life Bulb manufacturers typically provide an estimated bulb life for CFLs, generally listed in total
hours. Quality CFLs have a bulb life rating of 10,000 hours or more. The exact bulb life for a CFL will
vary depending on usage. For example, turning CFLs off and on frequently can shorten the lifespan.
Refer to the chart below to compare the power consumption of conventional incandescent bulbs and equivalent CFLs
When you want to set the right mood in a room, light output is only half of the equation. Two bulbs with equal brightness ratings can produce very different results if they have different color temperatures.
Bulb color temperature is rated in Kelvins. CFLs on the low end of the Kelvin scale emit a warmer, yellowish light, like a conventional incandescent bulb. CFLs with higher Kelvin numbers emit a bluer light, like conventional fluorescent lights. To maintain consistent light quality, it’s generally best to use only bulbs with the same color temperature in a single room.
Refer to the chart below for descriptions of the common CFL color categories:
Safety and Recycling
CFLs tubes contain a small amount of mercury, which is a toxic metal. On average, there are only 4 milligrams of mercury in a CFL bulb—a fraction of what you would find in a standard mercury thermometer or wristwatch battery. As long as the bulb is intact, the mercury is safely contained, but it’s important to avoid direct contact with a broken bulb. If you break a CFL, you should air out the room for 15 minutes. Then approach the cleanup carefully, following the Environmental Protection Agency’s recommended procedure, available at www.epa.gov/mercury/spills/.
Because of the mercury content, the EPA recommends consumers bring old CFLs to qualified recyclers, rather than disposing of them in trash cans or curbside recycling bins. Contact your local solid waste agency or visit www.epa.gov/bulbrecyling for guidelines on proper disposal in your area. You can bring old CFLs to The Home Depot for free recycling. Visit the Eco Options website to learn more.
If you’re concerned about the mercury content in CFLs, consider LED bulbs as an alternative energy-efficient solution. LEDs do not contain mercury and don’t have the same cleanup and disposable constraints. Refer to our LED Lighting Buying Guide to learn more.
• ENERGY STAR ® A label indicating the bulb meets stringent energy efficiency guidelines outlined by the
U.S. Department of Energy and the Environmental Protection Agency. CFLs that meet the ENERGY
STAR standard last about 10 times longer than an incandescent bulb and use 75% less energy than the
• Warranty – Many CFLs come with a warranty, covering replacement costs if the bulb malfunctions. To
display the Energy Star label, manufacturers must offer at least a two-year warranty. Many bulbs have
7-9 year warranties