Frequently Asked Questions on CFL Bulbs

What are Compact Fluorescent Light Bulbs?

CFL stands for Compact Fluorescent Light. We all know fluorescent lights, those long tubes that are used at work and in stores. In Compact Fluorescent Light bulbs, the long tubes are folded back and forth until they’re about the size of a regular incandescent light bulb so that they can be used in your regular fixtures. No changes need to be made to your lamps to use them since the ballast and other electronics are incorporated into the base of the bulb. However, CFLs cannot be used everywhere regular incandescent bulbs are used and special bulbs are needed for certain special applications.

How do CFLs work?

Regular incandescent bulbs produce light by passing a current through a thin conductor called a filament. This causes the filament to get so hot that it glows white, giving off light. Think of an electric stove and how you can see the metal heating elements glow red when a current passes through them. Incandescent bulbs are similar but the filament gets much, much hotter. To get the filament to glow white, it needs to be very hot so that most of the electric energy is used to make heat, not produce light. In fact incandescent bulbs are only about 6% efficient. CFLs work the same way as a fluorescent light works. The bulb is filled with a gas that gives off UV rays when excited by an electric signal. The UV rays then hit a phosphor coating on the inside of the bulbs causing it to glow and give off light. Since heat isn’t needed, these bulbs are much more efficient than incandescent, typically taking ¼ of the energy to produce the same amount of light.

Fluorescent bulbs have been around for years — why are CFLs getting popular now?

Until recently the technology didn’t exist to make the folded shape of the CFL, though we did have small donut shape rings and some other shapes. These were expensive and didn’t fit into many lamps. The new CFL bulbs are about the same size as the incandescent bulb they are replacing.

What are the benefits of CFLs?

CFLs have three huge benefits over incandescent. The first is power savings. With a CFL, you will use about 75% less electricity to get the same about of light compared to an incandescent bulb. The second benefit is that CFLs last up to 10 times longer than incandescent bulbs. This savings adds up very quickly, saving you $30 or more for each bulb you replace over the life of the bulb. And third, CFLs are also environmentally friendly. Using just one CFL will reduce the amount of CO2 going into the air by almost 700 lbs over the lifetime of the bulb. According to the government’s EnergyStar website “If every American home replaced just one light bulb with an EnergyStar qualified bulb, we would save enough energy to light more than 3 million homes for a year, more than $600 million in annual energy costs, and prevent greenhouse gases equivalent to the emissions of more than 800,000 cars.” These are big numbers and with a payback period of 4 months, it doesn’t make sense not to start using CFLs.

Where do CFLs work best?

It doesn’t make sense to replace all of your light bulbs with CFLs. You should only use CFL bulbs in lamps that are on about 3 hours or more a day and on more than 15 minutes at a time.

Where are CFLs NOT a good choice?

  • Lamps that are turned on and off frequently
  • Lamps that are subjected to vibration
  • Lamps that you do not use frequently
  • Lights on dimmers (see section on dimmable CFLs)
  • Recessed fully enclosed lights, since CFLs may get too hot
  • Open outside fixtures (enclosed outside fixtures are OK)
  • Lights on timers

What is available?

Today almost every shape and size CFL is available from many, many different CFL manufucatures. Due to the large selection, we recommend that you purchase only EnergyStar approved CFLs, which will help guarantee you get what you expect. We carry only GE EnergyStar approved products on this website so that you can shop with confidence.

What is Equivalent Wattage?

CFL bulb ‘brightness’ is often stated in terms of the Equivalent Wattage of an incandescent bulb. For example, a 60W incandescent bulb gives off about 800 lumens (an optical power measurment), however these bulbs are usually refered to by their electrical power (60W in this case) instead of optical power. The table below gives some common examples. Note that the CFL Wattage is typical only 25% of the Equivalent Wattage- a big power savings for the same brightness!

Incandescent Bulb Wattage

CFL Wattage

Minimum Light Output (lumens)
















What Does CFL Color Mean?

CFLs are available in two different color “shades”. The number in parentheses shows the approximate ‘color temperature’ for reference. See below for more information on color temperature.

  • Warm – Yellowish white light (2700K)
  • Daylight – Like daylight through a window (~6500K)

Most regular incandescent bulbs have a ‘warm’ light and would be replaced by a “warm’ CFL (2700K). You can also use ‘daylight’ bulbs for a whiter light. In general, the ‘warm’ lights highlight the red tones in the room and the ‘daylight’ bulbs will bring out more of the blue tones.

Do these bulbs flicker like the old fluorescent bulbs?

The CFL bulbs available on this site do not flicker and turn on immediately. They need to warm up over a few minutes to full brightness, though it is hard to see any change during this time. This is one reason why CFLs should be used in areas where the lights will be on for 15 minutes or more at a time.

A Word on Dimmable CFL’s

Special CFLs are made that can be used in a socket with a dimmer control. These bulbs are identified as “dimmable”. Regular CFLs are not dimmable and should not be used in dimmable sockets. We have tested the dimmable CFLs available and do not recommend them at this time. The main reason is that the light doesn’t turn down very much. Compared to the incandescents you and I are familiar with, that dim until they are almost totally off, the dimmable CFLs stay on quite bright when turned all the way down. Our recommendation is to continuing using incandescent bulbs for dimmers, and to wait to see if CFL dimmable bulbs improve before using them. Remember not to use regular CFLs in sockets that are connected to dimmers. These bulbs are not designed for this application and you can greatly shorten their life if used this way.

Biax® CFL’s

GE’s Biax® CFLs are extra long life CFLs, having a lifetime of 15,000 hours. These look a little different than the spiral shape of the standard CFLs: instead of a spiral, the tubes go straight up and down, making a “biaxial tube”.

What happens to the bulbs when they wear out?

In most causes when the bulbs reach their ‘end-of-life’ they simply stop working. In some cases the electronics in the base of the bulb will fail and, like a incandescent bulb, produce a popping noise and in some rarer cases a small amount of smoke. Bulbs on this site are designed to safely operate when this happens and are EnergyStar and UL approved. If this does happen just turn off the power to the bulb, wait for it to cool down, remove it by turning the base of the bulb, and replace it. Sound familiar? It’s the same procedure as a regular light bulb. Please check if you have special recycling requirements in your area for CFLs due to a trace amount of mecury inside the bulb. Just click on this link to check the options in your area If you are concerned about the use of mecury in CFLs, the actual total mecury emission of a CFL is almost 75% less than using incandescents. See the government’s EnergyStar website for more information on mecury at