Editing Compact fluorescent lamp (section)

==Characteristics==
===Spectrum of light===
[[File:Simple spectroscope.jpg|thumb|188px|right|Emitted visible light spectrum of an incandescent lamp (mid) and a CFL (bottom)]]
[[File:Spectral Power Distributions.png|thumb|Characteristic spectral power distributions (SPDs) for an incandescent lamp (left) and a CFL (right). The horizontal axes are in [[nanometer]]s and the vertical axes show relative intensity in arbitrary units. Significant peaks of UV light are present for CFL even if not visible.]]
[[File:CFBulbs.jpg|thumb|upright|A photograph of various lamps illustrates the effect of color temperature differences. From left to right:<br />{{•}} Compact Fluorescent (General Electric, 13&nbsp;W, 6500&nbsp;K)<br />{{•}} Incandescent (Sylvania, 60&nbsp;W, Extra Soft White)<br />{{•}} Compact Fluorescent (Bright Effects, 15&nbsp;W, 2644&nbsp;K<br />{{•}} Compact Fluorescent (Sylvania, 14&nbsp;W, 3000&nbsp;K)]]
CFLs emit light from a mix of [[phosphor]]s, each emitting one band of color with some bands still in the [[ultraviolet]] range as can be seen on the light spectrum. Modern [[fluorescent lamp#Phosphor composition|phosphor designs]] balance the emitted light color, energy efficiency, and cost. Every extra phosphor added to the coating mix improves color rendering but decreases efficiency and increases cost. Good quality consumer CFLs use three or four phosphors to achieve a "white" light with a [[color rendering index]] (CRI) of about 80, where the maximum 100 represents the appearance of colors under daylight or other sources of [[black-body radiation]] such as an [[incandescent light bulb]] (depending on the [[correlated color temperature]]).

[[Color temperature]] can be indicated in [[kelvin]]s or [[mired]]s (1 million divided by the color temperature in kelvins). The color temperature of a light source is the temperature of a [[black body]] that has the same [[chromaticity]] (i.e. color) as the light source. A notional temperature, the [[correlated color temperature]], the temperature of a black body that emits light of a hue that to human color perception most closely matches the light from the lamp, is assigned.

The color temperature is characteristic of black-body radiation; practical white light sources approximate the radiation of a black body at a given temperature, but will not have an identical spectrum. In particular, narrow bands of shorter-wavelength radiation are usually present even for lamps of low color temperature ("warm" light).<ref>[http://www.palagems.com/gem_lighting2.htm Buying and Selling Gems:What Light is Best? Part II: Artificial Light – The Options Available] See figures 6 and 7</ref>

As color temperature increases, the shading of the white light changes from red to yellow to white to blue. Color names used for modern CFLs and other tri-phosphor lamps vary between manufacturers, unlike the standardized names used with older halophosphate fluorescent lamps. For example, Sylvania's Daylight CFLs have a color temperature of 3500&nbsp;K, while most other lamps called ''daylight'' have color temperatures of at least 5000&nbsp;K. In United States, [[Energy Star]]'s specification provides a set of named color temperatures for certified luminaries.

{| class="wikitable"
|+Energy Star color temperatures<ref>{{cite web|title=Energy Star Program Requirements Product Specification for Luminaires 2.0|url=https://www.energystar.gov/sites/default/files/Luminaires%20V2%200%20Final_0.pdf|access-date=4 June 2017}}</ref>{{rp|26}}
|-
! rowspan=2 | Name
! colspan=2 | Color temperature
|-
! ([[Kelvin|K]])
! ([[Mired]])
|-
| Soft white ||style="background-color:#{{Color temperature|2700|hexval}}"| 2700 || 370
|-
| Warm white ||style="background-color:#{{Color temperature|3000|hexval}}"|  3000 || 333
|-
| Neutral White ||style="background-color:#{{Color temperature|3500|hexval}}"|  3500 || 286
|-
| Cool white
| style="background-color:#{{Color temperature|4050|hexval}}"|4000&mdash;4100
| 250&mdash;243
|-
| Daylight
| style="background-color:#{{Color temperature|5750|hexval}}"|5000&mdash;6500
| 200&mdash;154
|}

===Lifespan===
CFLs typically have a rated [[service life]] of 6000–15,000 hours, whereas standard [[Incandescent light bulb#Voltage, light output, and lifetime|incandescent lamps have a service life]] of 750 or 1000 hours.<ref>General Electric ''Incandescent lamps TP110'', technical pamphlet published in 1976, no ISBN or Library of Congress number, page 8</ref><ref>{{cite web |title=Osram Dulux EL Energy-Saving Lamps |publisher=Osram |access-date=2007-12-24 |url=http://www.osram.com/pdf/products/general/duluxsortiment.pdf |archive-date=2006-07-22|archive-url=https://web.archive.org/web/20060722104807/http://www.osram.com/pdf/products/general/duluxsortiment.pdf}}</ref><ref>{{cite web |title=IEC 60969: Self-ballasted lamps for general lighting services: Performance requirements |publisher=Collaborative Labelling and Appliance Standards Program |access-date=2007-12-24 |url=http://www.clasponline.org/teststandard.php?no=82|archive-url=https://web.archive.org/web/20080226083943/http://www.clasponline.org/teststandard.php?no=82|archive-date=February 26, 2008}}</ref> However, the actual lifetime of any lamp depends on many factors, including operating voltage, manufacturing defects, exposure to [[voltage spike]]s, [[Shock (mechanics)|mechanical shock]], frequency of cycling on and off, lamp orientation, and ambient [[operating temperature]], among other factors.<ref>{{cite web|last=Damir|first=B|title=Longevity of light bulbs and how to make them last longer|url=http://www.robaid.com/gadgets/longevity-of-light-bulbs-and-how-to-make-them-last-longer.htm|publisher=RobAid|access-date=4 January 2013|date=2012|url-status=dead|archive-url=https://web.archive.org/web/20150819081553/http://www.robaid.com/gadgets/longevity-of-light-bulbs-and-how-to-make-them-last-longer.htm|archive-date=19 August 2015}}</ref>

The life of a CFL is significantly shorter if it is turned on and off frequently or is used in a totally enclosed fixture. This happens because the electrodes in a CFL undergo sputtering every time it is turned on; this also happens in fluorescent tubes. Material from the electrodes is ejected every time sputtering occurs and it is deposited on the fluorescent tube's walls, showing as lamp end darkening. In the case of a 5-minute on/off cycle the lifespan of some CFLs may be reduced to that of incandescent light bulbs. The US [[Energy Star]] program suggests that fluorescent lamps be left on when leaving a room for less than 15 minutes to mitigate this problem.<ref name="energysavers-turn-off">{{cite web |title=When to turn off your lights |url=https://energy.gov/energysaver/when-turn-your-lights |work=Energy Saver |publisher=[[United States Department of Energy]] |access-date=2017-07-22}}</ref> CFLs emit less light later in their lives than when they are new. The light output decay is [[exponential decay|exponential]], with the fastest losses being soon after the lamp is first used. By the end of their lives, CFLs can be expected to emit 70–80% of their original light output.<ref>{{cite conference |last1=Guan |first1=Fumin |last2=Reynolds |first2=Dale |date=May 2005 |title=Topic and Discussions on the Performance Standard and Inspection Methods of CFL |url=http://www.rightlight6.org/english/proceedings/Session_8/Performance_Standard_and_Inspection_Methods_of_CFL/f013guan.doc |archive-url=https://web.archive.org/web/20070923124410/http://www.rightlight6.org/english/proceedings/Session_8/Performance_Standard_and_Inspection_Methods_of_CFL/f013guan.doc |archive-date=September 23, 2007 |conference=Right Light 6: 6th International Conference on Energy-Efficient Lighting |conference-url=https://web.archive.org/web/20070708071826/http://www.rightlight6.org/english}}</ref> The response of the human eye to light is [[Logarithmic scale|logarithmic]]. That is, while the human eye is highly sensitive to changes in the intensity of faint light sources, it is less sensitive to changes in the intensity of brighter light sources since the pupils compensate by dilating or constricting.<ref>{{cite news |last=Halsted |first=Charles P. |date=March 1993 |url=http://www.crompton.com/wa3dsp/light/lumin.html |title=Brightness, Luminance, and Confusion |access-date=2007-10-07 |work=Information Display |publisher=Naval Air Warfare Center Warminster, PA |quote=If the luminance of a viewed light source is increased 10 times, viewers do not judge that the brightness has increased 10 times. The relationship is, in fact, logarithmic: the sensitivity of the eye decreases rapidly as the luminance of the source increases. It is this characteristic that allows the human eye to operate over such an extremely wide range of light levels. |url-status=dead |archive-url=https://web.archive.org/web/20070922063502/http://www.crompton.com/wa3dsp/light/lumin.html |archive-date=September 22, 2007}}</ref> So, presuming the illumination provided by the lamp was ample at the beginning of its life, and the light output of a bulb gradually decreases by 25%, viewers will perceive a much smaller change in light intensity.<ref>{{cite thesis |type=PhD |last=Matković |first=Krešimir |date=December 1997 |url=http://www.cg.tuwien.ac.at/research/theses/matkovic/node15.html |title=Colour Science Basics: Human Vision |access-date=2007-10-07 |work=Tone Mapping Techniques and Color Image Difference in Global Illumination |publisher=Institut für Computergraphik eingereicht an der Technische Universität Wien ([[TU Wien]]) |quote=It is interesting, that despite that incoming light can have a dynamic range of nearly 14 log units, the neural units can transfer the signal having the dynamic range of only about 1.5 log units. It is obvious that there is some adaptation mechanism involved in our vision. It means that we adapt to some luminance value, and then we can perceive data in a certain dynamic range near the adaptation level. One of the most important characteristics that changes with different adaptation levels is the just noticeable difference. |archive-date=2021-06-09 |archive-url=https://web.archive.org/web/20210609115652/https://www.cg.tuwien.ac.at/research/theses/matkovic/node15.html |url-status=dead }}</ref>

Fluorescent lamps get dimmer over their lifetime,<ref>{{cite web|url=http://www.rightlight6.org/english/proceedings/Session_8/Performance_Standard_and_Inspection_Methods_of_CFL/s08-2p013guan.pdf |title=Topic and Discussions on the Performance Standard and Inspection Methods of CFL |access-date=2007-04-13 |url-status=dead |archive-url=https://web.archive.org/web/20070927202538/http://www.rightlight6.org/english/proceedings/Session_8/Performance_Standard_and_Inspection_Methods_of_CFL/s08-2p013guan.pdf |archive-date=September 27, 2007}}</ref> so what starts out as an adequate luminosity may become inadequate. In one test by the U.S. Department of Energy, of ''Energy Star'' products in 2003–04, one quarter of tested CFLs no longer met their rated output after 40% of their rated service life.<ref>{{cite journal |last1=O'Rourke |first1=Conan |last2=Zhou |first2=Yutao |year=2006 |url=http://www.osti.gov/bridge/servlets/purl/881039-K5YRuT/881039.PDF |title=Energy Star Lighting Verification Program (Program for the Evaluation and Analysis of Residential Lighting) Semi-annual report For the period of October 2003 to April 2004 |access-date=2007-04-13 |doi=10.2172/881039}}</ref><ref>{{cite web|url=http://mail.mtprog.com/CD_Layout/Day_2_22.06.06/1400-1545/ID133_Banwell_final.pdf |title=Quality Assurance in Energy Star Residential Lighting Programmes |access-date=2007-04-13 |url-status=dead |archive-url=https://web.archive.org/web/20061209005450/http://mail.mtprog.com/CD_Layout/Day_2_22.06.06/1400-1545/ID133_Banwell_final.pdf |archive-date=December 9, 2006}}</ref>

===Energy efficiency===
[[File:Electricity use by lightbulb type.svg|thumb|Energy use for different types of light bulbs operating at different light outputs. Points lower on the graph correspond to lower energy use.]]
{{Further|Luminous efficacy}}
Because the eye's sensitivity changes with the wavelength, the output of lamps is commonly measured in [[Lumen (unit)|lumens]], a measure of the power of light as perceived by the human eye. The [[luminous efficacy]] of lamps is the number of lumens emitted for each watt of electric power used. The [[luminous efficacy]] of a typical CFL is 50–70 lumens per watt (lm/W) and that of a typical incandescent lamp is {{nowrap|10–17 lm/W}}.<ref name=doelighting /> Compared to a theoretical 100%-efficient lamp ({{nowrap|680 lm/W}}), CFL lamps have lighting efficiency ranges of 7–10%,<ref>50/680 = 7%; 70/680 = 10%</ref> versus 1.5–2.5%<ref>10/680 = 1.5%; 17/680 = 2.5%</ref> for incandescents.<ref name="Keefe2007">{{cite web|last=Keefe |first=T. J. |title=The Nature of Light |url=http://www.ccri.edu/physics/keefe/light.htm |publisher=Community College of Rhode Island |access-date=18 September 2010 |date=2007 |url-status=dead |archive-url=https://web.archive.org/web/20100612002847/http://www.ccri.edu/physics/keefe/light.htm |archive-date=June 12, 2010}}</ref>

Because of their higher efficacy, CFLs use between one-seventh and one-third of the power of equivalent incandescent lamps.<ref name=doelighting>{{cite web |author=<!-- Unstated --> |title=Lighting |work=Energy Efficiency & Renewable Energy |publisher=[[United States Department of Energy]] |url=http://www.eere.energy.gov/basics/buildings/lighting.html |access-date=2 October 2011 |url-status=dead |archive-url=https://web.archive.org/web/20111015092547/http://www.eere.energy.gov/basics/buildings/lighting.html |archive-date=October 15, 2011}}</ref> Of 2010 world total lighting sales, 50 to 70 percent were incandescent.<ref>{{cite press release |author=<!-- Unstated --> |date=1 Dec 2010 |title=Multibillion dollar benefits of global switch to energy-efficient lighting |url=http://www.unep.org/Documents.Multilingual/Default.asp?DocumentID=651&ArticleID=6847&l=en&t=long |publisher=[[United Nations Environment Programme]] |access-date=2 October 2011 |archive-date=14 August 2016 |archive-url=https://web.archive.org/web/20160814025919/http://www.unep.org/Documents.Multilingual/Default.asp?DocumentID=651&ArticleID=6847&l=en&t=long |url-status=dead }}</ref> Replacing all inefficient lighting with CFLs would save {{convert|409|TWh|EJ|abbr=off|lk=on}} per year, 2.5% of world electricity use. In the US, it is estimated that replacing all incandescents would save 80 TWh yearly.<ref>{{cite web |title=United States of America |url=http://www.enlighten-initiative.org/portal/CountrySupport/CountryLightingAssessments/tabid/79083/Default.aspx |website=En.lighten |publisher=United Nations Environment Programme |access-date=2 October 2011 |author=<!-- Unstated. --> |date=2010 |url-status=dead |archive-url=https://web.archive.org/web/20120402032922/http://www.enlighten-initiative.org/portal/CountrySupport/CountryLightingAssessments/tabid/79083/Default.aspx |archive-date=April 2, 2012}}</ref> Since CFLs use much less energy than incandescent lamps (ILs), a phase-out of ILs would result in less [[carbon dioxide]] ({{CO2}}) being emitted into the atmosphere. Exchanging ILs for efficient CFLs on a global scale would achieve annual {{CO2}} reductions of 230 Mt (million tons), more than the combined yearly {{CO2}} emissions of the Netherlands and Portugal.<ref>{{Cite web|url=http://www.enlighten-initiative.org/portal/CountrySupport/CLAs/ClimateChangeMitigationBenefits/tabid/79155/Default.aspx|archive-url=https://web.archive.org/web/20130802043445/http://www.enlighten-initiative.org/portal/CountrySupport/CLAs/ClimateChangeMitigationBenefits/tabid/79155/Default.aspx|url-status=dead|title=Climate Change Mitigation Benefits|archive-date=August 2, 2013|website=www.enlighten-initiative.org}}</ref>

{| class="wikitable" style="text-align:center;"
|+ Electric power equivalents for differing lamps<ref name="estar">{{cite web |url=http://www.energystar.gov/index.cfm?c=cfls.pr_cfls_lumens |title=Learn About Light Output: Energy Star |publisher=Energystar.gov |access-date=2012-07-15}}</ref>
|-
! rowspan=2 | Minimum [[Luminous flux|light<br />output]] (lumens)
! colspan=3 | Electric power use (watts)
|-
! [[Incandescent light bulb|Incandescent]]
! Compact fluorescent
! [[Light-emitting diode|LED]]
|-
| 450
| 40
| 9–11
| 6–8
|-
| 800
| 60
| 13–15
| 9–12
|-
| 1100
| 75
| 18–20
| 13–16

|-
| 1600
| 100
| 23–28
| 15–22
|-
| 2400
| 150
| 30–52
| 24–28
|-
| 3100
| 200
| 49–75
| 30
|-
| 4000
| 300
| 75–100
| 38
|}
{{anchor|Heating and cooling}}
If a building's indoor incandescent lamps are replaced by CFLs, the heat emitted due to lighting is significantly reduced. In warm climates, or in office or industrial buildings where [[air conditioning]] is often required, CFLs reduce the load on the cooling system when compared to the use of incandescent lamps, resulting in savings in electricity in addition to the energy efficiency savings of the lamps. However, in cooler climates in which buildings require heating, the [[central heating|heating system]] must replace the reduced heat from lighting fixtures. In [[Winnipeg]], Canada, it was estimated that CFLs would only generate 17% savings in energy compared to incandescent bulbs, as opposed to the 75% savings that could have been expected without space heating considerations.<ref>{{cite news |url=http://www.cbc.ca/news/canada/manitoba/efficient-lighting-equals-higher-heat-bills-study-1.856047 |publisher=[[CBC News]] |title=Efficient lighting equals higher heat bills: study |date=2009-03-04}}</ref>

===Cost===
While the purchase price of a CFL is typically 3–10 times greater than that of an equivalent incandescent lamp, a CFL lasts 8–15 times longer and uses two-thirds to three-quarters less energy. A US article stated "A household that invested $90 in changing 30 fixtures to CFLs would save $440 to $1,500 over the five-year life of the bulbs, depending on your cost of electricity. Look at your utility bill and imagine a 12% discount to estimate the savings."<ref>{{cite news |last=Lavelle |first=Marianne |date=19 December 2007 |url=https://www.usnews.com/articles/business/economy/2007/12/19/faq-the-end-of-the-light-bulb-as-we-know-it.html |title=FAQ: The End of the Light Bulb as We Know It |work=[[U.S. News & World Report]]}}</ref>

CFLs are extremely cost-effective in commercial buildings when used to replace incandescent lamps. Using average U.S. commercial electricity and gas rates for 2006, a 2008 article found that replacing each 75 W incandescent lamp with a CFL resulted in yearly savings of $22 in energy usage, reduced [[HVAC]] cost, and reduced labour to change lamps. The incremental capital investment of $2 per fixture is typically paid back in about one month. Savings are greater and payback periods shorter in regions with higher electric rates and, to a lesser extent, also in regions with higher than U.S. average cooling requirements.<ref>{{cite web|url=http://www.energypulse.net/centers/article/article_display.cfm?a_id=1655 |title=The Cost-Effectiveness of Compact Fluorescents in Commercial Buildings |date=2008-01-23 |last=Chernoff |first=Harry |work=EnergyPulse |access-date=2008-03-21 |url-status=dead |archive-url=https://web.archive.org/web/20080220200101/http://www.energypulse.net/centers/article/article_display.cfm?a_id=1655 |archive-date=February 20, 2008}}</ref> However, frequent on-off cycling (turning on and off) of CFLs greatly reduces their lifespan.

The current price of CFLs reflects the manufacturing of nearly all CFLs in China, where labour costs less. In September 2010, the [[Winchester, Virginia]], [[General Electric]] plant closed,<ref name=Rourke>{{Cite news|url=https://www.washingtonpost.com/wp-dyn/content/article/2010/09/07/AR2010090706933.html|title=Light bulb factory closes; End of era for U.S. means more jobs overseas|last=Whoriskey|first=Peter|newspaper=[[The Washington Post]]|date=2010-09-08|access-date=2011-06-02}}</ref> leaving [[Osram Sylvania]] and the tiny American Light Bulb Manufacturing Inc. the last companies to make standard incandescent bulbs in the United States.<ref>{{cite news |last=Davenport |first=Jim |date=28 March 2011 |url=http://www.nbcnews.com/id/42312925 |archive-url=https://web.archive.org/web/20200313054826/http://www.nbcnews.com/id/42312925 |url-status=dead |archive-date=March 13, 2020 |title=SC lawmakers take dim view of new light bulbs |work=NBC News}}</ref> At that time, Ellis Yan, whose Chinese company made the majority of CFLs sold in the United States, said he was interested in building a United States factory to make CFL bulbs, but wanted $12.5 million from the U.S. government to do so. General Electric had considered changing one of its bulb plants to make CFLs, but said that even after a $40 million investment in converting a plant, wage differences would mean costs would be 50% higher.<ref name=Rourke />

According to an August 2009 newspaper report, some manufacturers claimed that CFLs could be used to replace higher-power incandescent lamps than justified by their light output.<ref>{{cite news |url=https://www.telegraph.co.uk/news/worldnews/europe/eu/6110547/Energy-saving-light-bulbs-offer-dim-future.html |archive-url=https://ghostarchive.org/archive/20220112/https://www.telegraph.co.uk/news/worldnews/europe/eu/6110547/Energy-saving-light-bulbs-offer-dim-future.html |archive-date=2022-01-12 |url-access=subscription |url-status=live |title=Energy saving light bulbs offer dim future |work=The Telegraph |date=29 August 2009 |first1=Richard |last1=Gray |first2=Julia |last2=McWatt}}{{cbignore}}</ref> Equivalent wattage claims can be replaced by comparison of actual light output emitted by the lamp, which is measured in lumens and marked on the packaging.<ref>{{cite web|url=http://europa.eu/rapid/pressReleasesAction.do?reference=MEMO/09/113 |title=Section III.3 |publisher=Europa.eu |access-date=2012-07-15}}</ref>
[[File:Compact fluorescent lamp wall mounted.JPG|thumb|Compact fluorescent lamp with wall-mounted holder]]

===Failure===
In addition to the wear-out failure modes common to all fluorescent lamps, the electronic ballast may fail, since it has a number of component parts. Ballast failures are usually due to overheating and may be accompanied by discoloration or distortion of the ballast enclosure, odors, or smoke.<ref>[http://www.halifax.ca/fire/documents/CFL.pdf Compact Fluorescent Lights], Halifax Regional Fire & Emergency {{webarchive |url=https://web.archive.org/web/20130520234142/http://www.halifax.ca/fire/documents/CFL.pdf |date=May 20, 2013}}</ref> The lamps are internally protected and are meant to fail safely at the end of their lives. Industry associations are working toward advising consumers of the different failure modes of CFLs compared to incandescent lamps, and to develop lamps with inoffensive failure modes.<ref>National Electrical Manufacturer's Association NEMA, ''[http://www.nema.org/stds/LSD40.cfm Failure Modes for Self-Ballasted Compact Fluorescent Lamps] (requires account) {{webarchive |url=https://web.archive.org/web/20120322051655/http://www.nema.org/stds/LSD40.cfm |date=March 22, 2012 |url-status=dead}}'', white paper no. LSD 40, retrieved 2008-06-26.</ref> New North American technical standards aim to eliminate smoke or excess heat at the end of lamp life.<ref>{{cite web|url=http://www.csa.ca/cm/ca/en/news/article/new-household-light-standard-addresses-consumer-concerns |title=New household lamp standards, discusses co-ordinated U.S., Mexico and Canada standard UL 1993, retrieved 2009 Dec 3 |publisher=Csa.ca |access-date=2012-07-15 |url-status=dead |archive-url=https://web.archive.org/web/20120315092721/http://www.csa.ca/cm/ca/en/news/article/new-household-light-standard-addresses-consumer-concerns |archive-date=2012-03-15}}</ref>

===Dimming===
[[File:Dimmable CFL.jpg|thumb|upright|Dimmable integrated helical CFL that dims 2–100%, comparable to standard light bulb dimming properties]]
Only some CFLs are labeled for [[Dimmer|dimming]] control. Using a dimmer with a standard CFL is ineffective and can shorten bulb life and void the warranty.<ref>[http://www.gelighting.com/na/home_lighting/ask_us/faq_compact.htm GE Lighting FAQ for CFL] retrieved 12 March 2007 {{webarchive |url=https://web.archive.org/web/20120626145829/http://www.gelighting.com/na/home_lighting/ask_us/faq_compact.htm |date=June 26, 2012}}</ref><ref>{{Cite web|url=https://www.energystar.gov/index.cfm?c=cfls.pr_cfls_warranty|title=CFL Warranty: Energy Star|website=www.energystar.gov|access-date=2019-12-18|archive-date=2020-03-16|archive-url=https://web.archive.org/web/20200316215517/https://www.energystar.gov/index.cfm?c=cfls.pr_cfls_warranty|url-status=dead}}</ref> Dimmable CFLs are available. The dimmer switch used in conjunction with a dimmable CFL must be matched to its power consumption range;<ref>{{Cite web|url=http://www.lutron.com/en-US/Education-Training/Pages/LCE/DimmingCFLsandLEDs.aspx|title=Dimming CFLs and LEDs|website=www.lutron.com}}</ref> many dimmers installed for use with incandescent bulbs do not function acceptably below 40&nbsp;W, whereas CFL applications commonly draw power in the range 7–20&nbsp;W. Dimmable CFLs have been marketed before suitable dimmers are available. The dimming range of CFLs is usually between 20% and 90%,<ref>{{cite web |url=http://www.dimmablecfls.com/ |title=Dimmable CFLs |publisher=Dimmable CFLs |access-date=2012-07-15 |archive-url=https://web.archive.org/web/20120621165133/http://www.dimmablecfls.com/ |archive-date=2012-06-21 |url-status=dead}}</ref>{{Unreliable source?|failed=y|date=October 2011}} but many modern CFLs have a dimmable range of 2% to 100%, more akin to that of incandescent lights. There are two types of dimmable CFL on the market: Standard dimmable CFLs, and "switch-dimmable" CFLs. The latter use a standard light switch, and the on-board electronics chooses the light output level based on the number of times the switch is turned on and off quickly. Dimmable CFLs are not a 100% replacement for incandescent fixtures that are dimmed for "mood scenes" such as [[Sconce (light fixture)|wall sconce]]s in a dining area. Below the 20% limit, the lamp may remain at 20% or flicker or the starter circuitry may stop and restart.<ref name=Yau2001>{{Cite book |last1=Yau |first1=E. K. F. |last2=Wing-Hung Ki |last3=Mok |first3=P. K. T. |last4=Sin |first4=J. K. O. |chapter=Phase-controlled dimmable CFL with PPFC and switching frequency modulation |title=2001 IEEE 32nd Annual Power Electronics Specialists Conference (IEEE Cat. No.01CH37230) |volume=2 |page=951 |year=2001 |isbn=978-0-7803-7067-8 |doi=10.1109/PESC.2001.954241 |s2cid=109878618}}</ref> Above 80%, the bulb may operate at 100%. However, recent products have solved these problems so that they perform more like incandescent lamps. Dimmable CFLs are more expensive than standard CFLs due to the additional circuitry.

[[Cold-cathode fluorescent lamp|Cold-cathode CFL]]s can be dimmed to low levels, making them popular replacements for incandescent bulbs on dimmer circuits.

When a CFL is dimmed, its color temperature (warmth) stays the same. This is counter to incandescent light sources, where color gets redder as the light source gets dimmer. The [[Kruithof curve]] from 1934 described an empirical relationship between intensity and color temperature of visually pleasing light sources.{{citation needed|date=June 2012}}

===Power factor===
[[File:CFL Positive power.png|thumb|right |Voltage and current for a 120 V 60 Hz 30-watt compact fluorescent lamp. Because the current is heavily distorted, the [[power factor]] of this lamp is only 0.61. The lamp takes 29 watts, but 39 [[volt-ampere]]s due to this distortion.]]
The input stage of a CFL is a rectifier, which presents a non-linear load to the power supply and introduces [[harmonic distortion]] on the current drawn from the supply.<ref>{{cite journal |first=Ph. N. |last=Korovesis |title=Influence of Large-Scale Installation of Energy Saving Lamps on the Line Voltage Distortion of a Weak Network Supplied by Photovoltaic Station |journal=IEEE Transactions on Power Delivery |volume=19 |issue=4 |pages=1787–1793 |year=2004 |doi=10.1109/TPWRD.2004.835432 |s2cid=19975088 |display-authors=etal}}</ref><ref>{{cite journal |first1=J. |last1=Cunill-Solà |first2=M. |last2=Salichs |title=Study and Characterization of Waveforms from Low-Watt (<25 W) Compact Fluorescent Lamps with Electronic Ballasts |journal=IEEE Transactions on Power Delivery |volume=22 |issue=4 |pages=2305–2311 |year=2007 |doi=10.1109/TPWRD.2007.899551 |s2cid=11439733}}</ref> The use of CFLs in homes has no appreciable effect on [[power quality]], but significant quantities of them in a large facility can have an adverse effect. The [[power factor]] of CFLs does not significantly affect their energy-saving benefits for individual consumers, but their use in large numbers, such as in commercial applications or across millions of homes in a distribution system, could require infrastructure upgrades. In such cases, CFLs with low (below 30 percent) [[Harmonics (electrical power)|total harmonic distortion]] (THD) and power factors greater than 0.9 should be selected.<ref>{{cite web |url=http://www.mge.com/business/saving/madison/pa_2.html |title=Compact Fluorescent Lamps |publisher=Mge.com |access-date=2012-07-15 |archive-url=https://web.archive.org/web/20120314091500/http://www.mge.com/business/saving/madison/pa_2.html |archive-date=2012-03-14 |url-status=dead}}</ref><ref>Anibal T. De Almeida: ''[http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/93/931113.html Understanding Power Quality] {{Webarchive|url=https://web.archive.org/web/20110726153320/http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/93/931113.html |date=2011-07-26 }}'', ''Home Energy Magazine''</ref><ref>{{Cite report |url=http://www.energy.ca.gov/2007_energypolicy/documents/2007-06-19_workshop/comments/1-Fernstrom_PGE_Residential-Lighting-Improvement-Opportunities.pdf |title=Residential Lighting Improvement Opportunities |last=Fernstrom |first=Gary B. |date=June 19, 2007 |publisher=[[California Energy Commission]] |url-status=dead |archive-url=https://web.archive.org/web/20120723091715/http://www.energy.ca.gov/2007_energypolicy/documents/2007-06-19_workshop/comments/1-Fernstrom_PGE_Residential-Lighting-Improvement-Opportunities.pdf |archive-date=July 23, 2012 |quote=Joint Committee Workshop on Policies to Improve Residential Lighting Efficiency in California}}</ref>

===Infrared signals===
Electronic devices operated by [[infrared remote control]] can interpret the infrared light emitted by CFLs as a signal; this may limit the use of CFLs near televisions, radios, remote controls, or [[mobile phone]]s. [[Energy Star]] certified CFLs must meet FCC standards, and so are required to list all known incompatibilities on the package.<ref name=autogenerated1>[http://blogs.consumerreports.org/home/2007/11/cfl-problems.html Can CFLs interfere with electronic equipment?] {{webarchive |url=https://web.archive.org/web/20101029161424/http://blogs.consumerreports.org/home/2007/11/cfl-problems.html |date=October 29, 2010}} at ConsumerReports.org. Accessed 1 January 2008.</ref><ref>{{cite web |url=http://www.energystar.gov/index.cfm?c=cfls.pr_crit_cfls |title=Compact Fluorescent Light Bulbs Key Product Criteria: Energy Star |publisher=Energystar.gov |date=2008-12-02 |access-date=2012-07-15 |archive-date=2012-07-13 |archive-url=https://web.archive.org/web/20120713030505/http://www.energystar.gov/index.cfm?c=cfls.pr_crit_cfls |url-status=dead }}</ref>

===Outdoor use===
[[File:A CFL Light Bulb on a wall in a black lantern in South Carolina.PNG|thumb|upright|A CFL used outside of a building]]
CFLs are generally not designed or rated for outdoor use and some will not start in cold weather. CFLs are available with cold-weather ballasts, which may be rated to as low as −28.8&nbsp;°C (−20&nbsp;°F).<ref>{{cite web|url=http://www.cleanairpartnership.org/cleanairguide/terms_definitions.htm|title=Coming to Terms with Energy Efficiency and the Environment|publisher=The Clean Air Partnership|archive-url=https://web.archive.org/web/20071011064253/http://cleanairpartnership.org/cleanairguide/terms_definitions.htm|archive-date=October 11, 2007}}</ref> Light output during the first few minutes of operation is limited at low temperatures before reaching full brightness.<ref>U.S. Dept. of Energy, Greening Federal Facilities, 2nd Edition, '[http://www1.eere.energy.gov/femp/pdfs/29267-5.4.3.pdf Compact Fluorescent Lighting] {{webarchive |url=https://web.archive.org/web/20110511132153/http://www1.eere.energy.gov/femp/pdfs/29267-5.4.3.pdf |date=May 11, 2011}}'. DOE/GO=102001-1165 page 87. Retrieved 22 February 2007. "Even when low-temperature ballasts are used, lamps will not reach full brightness for several minutes in cold weather."</ref> [[Cold-cathode fluorescent lamp|Cold-cathode CFL]]s will start and perform in a wide range of temperatures due to their different design.

===Starting time===
Incandescent lamps reach full brightness a fraction of a second after being switched on. {{As of|2009}}, CFLs turn on within a second, but many still take time to achieve full brightness.<ref>{{cite web|url=http://www.gelighting.com/na/home_lighting/ask_us/faq_compact.htm#flicker |title=Why does my compact fluorescent light bulb flicker or appear dim when I first turn it on? |work=Compact Fluorescent Light Bulb (CFL) FAQs |publisher=GE Lighting |access-date=2009-06-15 |url-status=dead |archive-url=https://web.archive.org/web/20090228044819/http://www.gelighting.com/na/home_lighting/ask_us/faq_compact.htm |archive-date=February 28, 2009}}</ref> The light color may be slightly different immediately after being turned on.<ref>{{cite web|url=http://www.gelighting.com/na/business_lighting/faqs/cfl.htm |title=GE Lighting Frequently Asked Questions&nbsp;— Compact Fluorescent (CFL): 4. Can I use a CFL in applications where I will be turning the lights on/off frequently? |access-date=2007-04-13 |url-status=dead |archive-url=https://web.archive.org/web/20070329191437/http://www.gelighting.com/na/business_lighting/faqs/cfl.htm |archive-date=March 29, 2007}}</ref> Some CFLs are marketed as "instant on" and have no noticeable warm-up period,<ref name="EnergyStarFaq-WarmUp">{{cite web |url=https://energystar.zendesk.com/hc/en-us/articles/212110657-I-ve-noticed-some-CFLs-need-a-few-minutes-to-warm-up-or-reach-full-brightness-Is-there-a-way-to-determine-which-warm-up-fastest- |title=I've noticed some CFLs need a few minutes to warm up, or reach full brightness&nbsp;... |work=Customer Help FAQ |publisher=Energy Star |access-date=2009-06-15 |archive-url=https://web.archive.org/web/20170324083650/https://energystar.zendesk.com/hc/en-us/articles/212110657-I-ve-noticed-some-CFLs-need-a-few-minutes-to-warm-up-or-reach-full-brightness-Is-there-a-way-to-determine-which-warm-up-fastest- |archive-date=2017-03-24 |url-status=bot: unknown }}</ref> but others can take up to a minute to reach full brightness,<ref>{{cite web |url=http://www.fcgov.com/conservation/lighting-faq.php |title=Why does it take time for CFL bulbs to come up to full brightness? |work=Efficient Lighting FAQs |publisher=City of Fort Collins |access-date=2009-06-15 |url-status=dead |archive-url=https://web.archive.org/web/20081210045249/http://www.fcgov.com/conservation/lighting-faq.php |archive-date=December 10, 2008}}</ref> or longer in very cold temperatures. Some that use a mercury [[amalgam (chemistry)|amalgam]] can take up to three minutes to reach full output.<ref name="EnergyStarFaq-WarmUp" /> This and the shorter life of CFLs when turned on and off for short periods may make CFLs less suitable for applications such as motion-activated lighting. Hybrid lamps, combining a halogen lamp with a CFL, are available where warm up time is unacceptable.<ref>{{cite web | url=https://www.ledsmagazine.com/home/article/16700874/ge-lighting-to-promote-halogen-cfl-hybrid-bulb-with-target | title=GE Lighting to promote halogen-CFL hybrid bulb with Target | date=5 September 2013 }}</ref> The halogen lamp lights immediately, and is switched off once the CFL has reached full brightness.