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Keyword Exclusive – Compact Fluorescent Light Bulbs

Supplement to “Letters – Spotlight on energy-saving bulbs”

Responses to technical concerns about CFLs

Kentucky Living received letters to the editor raising several serious questions about compact fluorescent light bulbs, in response to the June 2007 From the Editor column, “A new light,” which promoted the energy savings of CFLs.

The top concern of those letters related to disposing of the bulbs, which contain mercury. Good information on CFL disposal can be found at, by phoning (877) EARTH-911, or visiting

Other questions related to usefulness around the home, including compatibility with different fixtures, color and light level, and even the bulbs causing headaches and whether any are made in the United States.

Kentucky Living submitted the reader concerns to Service Concepts, an Indianapolis-based co-op that provides various technical services for electric co-ops around the country. Among their activities, they provide the compact fluorescent bulbs that many Kentucky electric co-ops give away at their annual meetings.

Service Concepts responded to the Kentucky Living reader concerns with an in-depth, point-by-point analysis of each area. Here is that analysis:

General comment: There is more variety among compact fluorescent lamps than among incandescent lamps. CFLs vary in light output, mean life, color “temperature,” manufacturing quality, cold-start temperature, warm-up time, and efficiency. It is true that different CFLs, with different specs, by different manufacturers, may produce visually different light.

The key measures for CFLs include lumen output, lumen maintenance (over the life of the lamp), color temperature, cold-start minimum temperature, and lumens per watt.

Lumens are a measure of light output. Incandescent 60-watt bulbs emit between 800 and 890 lumens. Kentucky’s UB14 CFLs produce 800 lumens. Next year’s model is committed to produce 900 lumens for the same 14 watts consumed. Depending on the incandescent bulb used for comparison, there may be a slight perceived difference in light output, just as comparing two different incandescent bulbs may show a slight difference. (Once the incandescent bulb burns out, of course, the CFL will have several remaining years of advantage.)

Color Temperature is a scale for defining the “warmth” or “coolness” of a lamp’s light. The actual scale, expressed in “degrees K,” is based on the color of light generated by a bar of iron heated to various temperatures on the Kelvin (absolute zero) scale. The light put out by an incandescent lamp most closely resembles the color of the light that would be emitted by that bar of iron if it were heated to 2,700 degrees (Kelvin). If that bar were heated to higher temperatures, the “color temperature” of the light would shed some of its warmer tones (reds and yellows) and take on more cool tones (blues), eventually achieving a light most approximating the full spectrum color range of sunlight at around 6,000 degrees K.

EPA/Energy Star has set down standards (find details on those standards at for CFLs to achieve the Energy Star rating, with the goal of making a class of CFLs that most closely approximate the light output of an incandescent bulb (to maximize consumer acceptance). Engineers are able to control the color temperature of a CFL through the design of the phosphors that glow in the tube. Energy Star’s target is 2,700 to 3,000 degrees Kelvin (commonly: 2700K to 3,000K.) It is entirely possible that CFLs from different manufacturers may have a different light appearance. The Energy Star logo should at least minimize the range of those differences, though. If a CFL carries the Energy Star logo, and does not say otherwise, it should have a color temperature between 2700K and 3000K. It is OK for a CFL to carry the Energy Star logo and have a higher color temperature, but in that case the package must specifically state the temperature and color of the CFL (warm or cool.)

For comparison, while a typical household incandescent equivalent CFL should be around 2700K, a typical office fluorescent tube is likely to be 4100K, a typical warehouse is likely to be 5100K, and a “full spectrum” or “sunlight” type CFL may be as high as 5500-6000K. The term “bright white” is not a defined term other than in marketing lingo, and is generally used to refer to lamps with color temperature in the 3000K to 5000K range. TCP produces a 4100K version of its Utility Bulb line, although these are generally used in commercial applications and have not been submitted for consumer Energy Star rating.

Related to Color Temperature is Color Rendition, and its index (CRI) is a measure of the color appearance of an object under a light in conscious or subconscious comparison with their color appearance under a reference light source of comparable color temperature (in this case, an incandescent bulb). Energy Star’s requirement is a CRI of greater than 80 on a 100 point scale, which suggests that an Energy Star CFL’s color rendition will be very good, but there will potentially be some perceived differences when compared with incandescent light.

All CFLs, by the science that enables them, require some amount of warm-up time. All quality CFLs should start instantly, with no flicker, but will require anywhere from 30 seconds to a couple of minutes to warm up to full lumen output. It is possible to engineer the tradeoffs between instant brightness and other features such as maximum brightness and expected service life. There are specialty CFLs such as the TCP “InstaBright” line (details at that give priority to first-second brightness vs. expected life—at a higher cost.

Most CFLs on the market are rated for reliable startup at ambient temperatures down to -10 degrees F. TCP CFLs are designed to reliably start at ambient temperatures down to -20 degrees F. In extremely low ambient temperature environments, CFLs may not produce as many lumens of brightness as they would at normal room temperatures. In such cases, it could be useful to move up to the next higher rated CFL for acceptable light output. The extremes of low ambient temperature and high operating temperature of incandescent bulbs can lead to earlier failure of the incandescents, so the long-term advantage of a CFL in low temperature environments is one of reliability and lifetime service as well as energy savings.

Because of the additional layer of frosted glass involved, the flood, globe, and A-lamp (traditional bulb shape) CFLs will appear to be even dimmer at startup, and/or require a longer warm-up time. With startup-level light output and two, rather than one, thicknesses of glass to glow through, the warm-up process for these covered CFLs will be more noticeable to the consumer at first. Once the CFL is fully warmed up, the lamp should produce its rated lumen output and appear to be as bright and functional as an incandescent flood or globe of comparable lumen output.

The headache story should be obsolete, dating back to reported experiences during the days of magnetic fluorescent ballasts. Such ballasts would pulse energy in the fluorescent tube at the same 60-cycle rate as the AC current provided. Today’s modern electronic ballasts operate in the range of 20,000 Hertz, which should be well beyond the human brain’s ability to distinguish. By comparison, a typical CRT monitor’s refresh rate will be between 60-85 Hz, and a television’s refresh rate is 59.94 Hz. While watching TV in the presence of a magnetic ballasted fluorescent lamp might present some visual challenges, a modern electronic ballasted office fixture or a CFL (which by necessity requires a compact electronic ballast) should have no adverse effects.

Most CFLs should not be used on circuits with dimmers, electronic timers, and photocell devices. This is all correct. They are designed to function within a range of constant expected voltage, and do so efficiently. Dimming a standard CFL would be analogous to using radio on a circuit with a dimmer to control the volume. Both the radio and the CFL are complex electronic devices. Reducing the voltage would result in stress and eventual failure of its circuitry. Timers and photocells are included with dimmers in the “do not” category because they often leak a small amount of current in order to power the timer or photocell function. That low level of leaked current passes unnoticed through an incandescent bulb without creating noticeable heat or light, but the trickle of current through a CFL will have the same effect as a dimmer—premature failure.

While most CFLs are designed for use on standard circuits without dimmers & timers, to provide energy-efficient light at the lowest possible consumer cost, there are CFL models designed to be used with dimmers. The engineering challenge is significant. Their electronic ballasts are more complex and costly. Consumers are not forced to pay for the extra circuitry and manufacturing cost to be included in every CFL, including those which will not be used on dimmers. As the science and engineering progress, costs will come down on dimmable CFLs, just as a $15 standard CFL in 1995 has become $3 in 2007 (and more efficient as well). TCP manufactures several impressive dimmable CFL models, but the $15-$20 consumer cost keeps them outside the range that most consumers and cooperatives are interested in talking about now.

There is no reason that CFLs cannot be used in recessed fixtures. Many of TCP’s CFL models are produced with the expectation that they will be used in recessed fixtures such as track lights and ceiling cans.

The caution against using CFLs in enclosed fixtures has merit. TCP’s rule of thumb: Do not enclose an enclosed CFL. This means that a CFL that is already enclosed in glass, such as a flood or globe or A-lamp, should not be further enclosed in a closed fixture. Enclosed ceiling fixtures, for example, should be equipped with standard (bare) springlamps.

There are two exceptions to this rule of thumb. TCP does not recommend enclosing CFLs greater than 23 watts in size. Also, these limitations apply to indoor fixtures only. It is OK to put an enclosed (or bare, for that matter) CFL in an enclosed outdoor fixture such as a porch light or lamppost fixture. The purpose of these recommendations in each case has to do with ventilation and heat buildup. All CFLs operate at significantly lower temperatures than their incandescent counterparts. Even so, the life of a CFL can be adversely affected by high unventilated ambient temperatures. Outdoor fixtures typically allow enough airflow to avoid temperature concerns. All TCP enclosed CFLs (floods, globes, and A-lamps) are approved for outdoor use as long as they are protected from direct water exposure such as rain or spray.

High vibration installations such as garage door openers or unbalanced ceiling fans may reduce a CFL’s life. They may also reduce an incandescent bulb’s life. The CFL in my garage door opener may not survive its 9-year warranty, but it has long outlasted the previous incandescents it replaced. I won’t try to make a warranty claim if it fails after 2 or 5 or 7 years, but will appreciate the energy and ladder (replacement) time it will have saved me.

CFLs are devices with characteristics that, like most things in life, present tradeoffs. As lighting accounts for somewhere between 10 percent and 30 percent of a household’s electricity consumption, and CFLs can offer up to 75 percent reduction in that portion of ifs energy bill, most consumers are happy to adjust to the warm-up time of a CFL in return for those savings. Some are not. CFLs are not designed for, or cost-effective for, all household lighting applications. They are cost-effective (more info at and available for most household lighting applications (more info at, however.

All TCP CFLs provided to Kentucky cooperatives through KAEC carry a one-year factory warranty. They are made by the same company on the same production lines that produce our longest (9-year) warranty products. They are designed and produced to the same 10,000-hour life expectancy standards. And while I am sure that there have been failures, I am not aware of a single warranty claim or report of trouble from the large number of CFLs distributed through KAEC during the past several years.

Unfortunately, there are no compact fluorescent bulbs made by any manufacturer in the US.

Not all CFLs are made the same. TCP is the only manufacturer to my knowledge that does not contract out some portion of production 3rd-party factories scattered among many countries. They own and control every part of the process on both ends, from the sand that goes into the glass, to the warehouse dock in Ohio where the truck leaves for your facility. For cooperative markets, owned by their consumers, we work exclusively with TCP as we have direct access to those with quality responsibility in every stage of the design and production processes. They know that quality is king in our market, and their success depends on continually delivering both outstanding product quality and best-in-class customer service.

Bottom line: There are no panaceas. There are, however, plenty of good things to do. Using CFLs will reduce electric bills, reduce energy consumption, reduce greenhouse gas and mercury emissions, reduce the need for additional generation and transmission capacity, reduce air conditioning load in the warm months, reduce peak load in some residential systems, and reduce the volume of metal and glass tossed into our landfills. Using CFLs wherever appropriate is a good thing to do.

Here are some additional Energy Star links that would be useful, especially the FAQ:

Then choose “Lighting (CFLs, Bulbs, Fixtures)” from the Search drop-down menu

Business Payback Calculator:

About CFLs:

5 steps you can take:

Purchasing tips:

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