Editing Incandescent light bulb (section)

==Efficacy and efficiency==
{{further|Luminous efficacy}}
[[File:2200K Spectrum.jpg|thumb|Spectrum of an incandescent lamp at 2200&nbsp;K, showing most of its emission as invisible [[infrared]] light]]
[[File:Thermal image of an incandescent light.jpg|thumb|Thermal image of an incandescent bulb. {{convert|22|–|175|C|F}}. Most of the mid and far-IR is absorbed by the glass, heating it to scorching temperatures. This heats the surrounding air, which rises, helping cool the bulb from the bottom up.]]
Less than 5% of the power consumed by a typical incandescent light bulb is converted into visible light, with most of the rest being emitted as invisible infrared radiation.<ref name="incandescent"/><ref>''Handbook of Digital Image Synthesis'' by Vincent Pegoraro - CRC Press 2017 Page 690</ref> Light bulbs are rated by their [[luminous efficacy]], which is the ratio of the amount of visible light emitted ([[luminous flux]]) to the electrical power consumed.<ref>{{cite book |title=IEEE Standard 100: definition of luminous efficacy |page=647}}</ref> Luminous efficacy is measured in [[Lumen (unit)|lumens]] per watt (lm/W).

The luminous ''efficiency'' of a source is defined as the ratio of its luminous efficacy to the maximum possible luminous efficacy, which is 683&nbsp;lm/W.<ref>{{cite web |url=http://www.yuvaengineers.com/end-of-incandescent-light-bulb/ |title=End of Incandescent Light Bulb |publisher=yuvaengineers.com |date=23 June 2012 |access-date=7 March 2017 |url-status=live |archive-url=https://web.archive.org/web/20170307124220/http://www.yuvaengineers.com/end-of-incandescent-light-bulb/ |archive-date=7 March 2017}}</ref><ref>{{cite web |url=http://www.kse-lights.co.uk/the-energy-efficiency-of-light-bulbs-today-compared-to-the-past/ |title=The Energy Efficiency of Light Bulbs Today Compared to the Past |publisher=kse-lights.co.uk |date=13 February 2017 |access-date=7 March 2017 |url-status=dead |archive-url=https://web.archive.org/web/20170307123653/http://www.kse-lights.co.uk/the-energy-efficiency-of-light-bulbs-today-compared-to-the-past/ |archive-date=7 March 2017}}</ref> An ideal white light source could produce about 250 lumens per watt, corresponding to a luminous efficiency of 37%.<ref name="max-eff-truncated-1">
{{cite journal|doi=10.1063/1.4721897
| title=Maximum spectral luminous efficacy of white light|journal=Journal of Applied Physics
| volume=111 | issue=10 | year=2012
| last1=Murphy | first1=Thomas W.
| pages=104909–104909–6| arxiv = 1309.7039
| bibcode = 2012JAP...111j4909M
| s2cid=6543030}}</ref>

For a given quantity of light, an incandescent light bulb consumes more power and emits more heat than most other types of electric light. In buildings where [[air conditioning]] is used, incandescent lamps' heat output increases load on the air conditioning system.<ref>Peter Lund, Helsinki University of Technology, on p. C5 in [[Helsingin Sanomat]] 23 October 2007.</ref> While heat from lights will reduce the need to run a building's heating system, the latter can usually produce the same amount of heat at lower cost than incandescent lights.

The chart below lists the luminous efficacy and efficiency for several types of incandescent bulb. A longer chart in [[Luminous efficacy#Overall luminous efficacy|luminous efficacy]] compares a broader array of light sources. 
{| class="wikitable"
|-
!Type||Overall luminous efficiency||Overall luminous efficacy (lm/W)
|-
|40&nbsp;W tungsten incandescent (120 V, general service)
|1.9%
|12.6<ref name="incandescent"/>
|-
|60&nbsp;W tungsten incandescent (120 V, general service)
|2.1%
|14.5<ref name="incandescent"/>
|-
|100&nbsp;W tungsten incandescent (120 V, general service)
|2.6%
|17.5<ref name="incandescent"/>
|-
|Glass halogen
|2.3%
|16
|-
|Quartz halogen
|3.5%
|24
|-
|Photographic and projection lamps with very high filament temperatures and short lifetimes
|5.1%
|35<ref name="bulbguide">{{cite web|author=Klipstein, Donald L. |year=1996 |title=The Great Internet Light Bulb Book, Part I |url=http://freespace.virgin.net/tom.baldwin/bulbguide.html|url-status=dead |archive-url=https://web.archive.org/web/20060502061149/http://freespace.virgin.net/tom.baldwin/bulbguide.html |archive-date=2 May 2006}}</ref>
|-
|Theoretical maximum for a tungsten filament incandescent bulb
|7.6%
|52<ref name="GETP110" />
|}

===Color rendering===
The spectrum of light produced by an incandescent lamp closely approximates that of a [[black body radiator]] at the same temperature.<ref name="Edison_Incandescent">{{cite web|url=http://www.edisontechcenter.org/incandescent.html |title=Incandescent Lamps |work=edisontechcenter.org |url-status=dead |archive-url=https://web.archive.org/web/20130314112308/http://www.edisontechcenter.org/incandescent.html |archive-date=14 March 2013}}</ref> The basis for light sources used as the standard for color perception is a tungsten incandescent lamp operating at a defined temperature.<ref>Janos Schanda (ed), ''Colorimetry: Understanding the CIE System'', John Wiley & Sons, 2007 {{ISBN|0470175621}} page 44</ref>
[[File:Spectral power distribution of a 25 W incandescent light bulb.png|thumb|Spectral power distribution of a 25&nbsp;W incandescent light bulb.]]

Light sources such as fluorescent lamps, [[high-intensity discharge lamp]]s and [[LED lamp]]s have higher luminous efficiency. These devices produce light by [[luminescence]]. Their light has bands of characteristic wavelengths, without the "tail" of invisible infrared emissions, instead of the continuous spectrum produced by a thermal source. By careful selection of fluorescent phosphor coatings or filters which modify the spectral distribution, the spectrum emitted can be tuned to mimic the appearance of incandescent sources, or other different [[color temperature]]s of white light. When used for tasks sensitive to color, such as motion picture lighting, these sources may require particular techniques to duplicate the appearance of incandescent lighting.<ref>Blain Brown, ''Motion Picture and Video Lighting'', Routledge, 2018, {{ISBN|0429866666}} Chapter 7</ref> [[Metamerism (color)|Metamerism]] describes the effect of different light spectrum distributions on the perception of color.

===Cost of lighting===
{{See also|Architectural lighting design}}
The initial cost of an incandescent bulb is small compared to the cost of the energy it uses over its lifetime. Incandescent bulbs have a shorter life than most other lighting, an important factor if replacement is inconvenient or expensive. Some types of lamp, including incandescent and fluorescent, emit less light as they age; this may be an inconvenience, or may reduce effective lifetime due to lamp replacement before total failure. A comparison of incandescent lamp operating cost with other light sources must include illumination requirements, cost of the lamp and labor cost to replace lamps (taking into account effective lamp lifetime), cost of electricity used, effect of lamp operation on heating and air conditioning systems. When used for lighting in houses and commercial buildings, the energy lost to heat can significantly increase the energy required by a building's [[air conditioning]] system. During the heating season heat produced by the bulbs is not wasted,<ref>{{cite news | url=https://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=4 March 2009 | url-status=live | archive-url=https://web.archive.org/web/20110214132113/https://www.cbc.ca/news/canada/manitoba/efficient-lighting-equals-higher-heat-bills-study-1.856047 | archive-date=14 February 2011}}</ref> although in most cases it is more cost effective to obtain heat from the heating system. Regardless, over the course of a year a more efficient lighting system saves energy in nearly all climates.<ref name=cmhc>{{cite web |url=http://www.cmhc.ca/odpub/pdf/65830.pdf |title=Benchmarking Home Energy Savings from Energy-Efficient Lighting |date=January 2008 |author=Anil Parekh |publisher=Canada Mortgage and Housing Corporation |access-date=14 January 2016 |url-status=dead |archive-url=https://web.archive.org/web/20160130112609/http://www.cmhc.ca/odpub/pdf/65830.pdf |archive-date=30 January 2016}}</ref>

===Measures to ban use===
{{Main|Phase-out of incandescent light bulbs}}
Since incandescent light bulbs use more energy than alternatives such as [[compact fluorescent lamp|CFL]]s and [[LED lamp]]s, many governments have introduced measures to ban their use, by setting minimum efficacy standards higher than can be achieved by incandescent lamps. Measures to ban light bulbs have been implemented in the European Union, the United States, Russia, Brazil, Argentina, Canada and Australia, among others. The European Commission has calculated that the ban contributes {{Euro|5{{nbsp}}billion}} to {{Euro|10{{nbsp}}billion}} to the economy and saves 40&nbsp;TWh of electricity every year, translating in {{CO2}} emission reductions of {{convert|15|e6t|e9lb|abbr=off}}.<ref>Nicholas A. A.Howarth, Jan Rosenow: ''Banning the bulb: Institutional evolution and the phased ban of incandescent lighting in Germany''. In: ''[[Energy Policy (journal)|Energy Policy]]'' 67, (2014), 737–746, {{doi|10.1016/j.enpol.2013.11.060}}.</ref><ref>{{cite web |title=Frequently asked questions about the regulation on ecodesign requirements for non-directional household lamps |url=https://ec.europa.eu/commission/presscorner/detail/en/MEMO_09_113 |website=European Commission - European Commission |access-date=19 August 2022 |language=en}}</ref>

Objections to banning the use of incandescent light bulbs include the higher initial cost of alternatives and lower quality of light of fluorescent lamps.<ref name=NYT>{{Cite news |url=https://www.nytimes.com/2009/07/06/business/energy-environment/06bulbs.html |author=Leora Broydo Vestel |work=The New York Times |title=Incandescent Bulbs Return to the Cutting Edge |date=6 July 2009|url-status=live |archive-url=https://web.archive.org/web/20110512214719/http://www.nytimes.com/2009/07/06/business/energy-environment/06bulbs.html |archive-date=12 May 2011}}</ref> Some people have concerns about the [[Fluorescent lamps and health|health effects]] of fluorescent lamps.<ref name=scenihr2008>{{cite web |url=http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_019.pdf |archive-url=https://web.archive.org/web/20081112081741/http://ec.europa.eu/health/ph_risk/committees/04_scenihr/docs/scenihr_o_019.pdf |archive-date=2008-11-12 |url-status=live|title=Light Sensitivity, Scientific Committee on Emerging and Newly Identified Health Risks|access-date=2009-08-31|publisher=Director-General for Health and Consumers, European Commission|date=2008|pages=26–27}}</ref>

===Efforts to improve efficacy===
[[File:Wolfram-Halogenglühlampe.png|thumb|upright|Xenon [[halogen lamp]] with an E27 base, which can replace a non-halogen bulb]]
Some research has been carried out to improve the efficacy of commercial incandescent lamps. In 2007, [[General Electric]] announced a ''high efficiency incandescent'' (HEI) lamp project, which they claimed would ultimately be as much as four times more efficient than current incandescents, although their initial production goal was to be approximately twice as efficient.<ref name=notsodim>{{Cite web|last=Daley |first=Dan |date=27 February 2008 |title=Incandescent's Not-So-Dim Future |url=https://plsn.com/articles/the-biz/incandescents-not-so-dim-future/|url-status=live|work=Projection, Lights & Staging News |volume=09 |issue=1 |page=46 |publisher=Timeless Communications Corp|archive-url=https://web.archive.org/web/20140306230206/http://www.plsn.com/current-issue/31-the-biz/2520-incandescents-not-so-dim-future.html |archive-date=6 March 2014}}</ref><ref>{{cite press release |last=Freeman |first=Kim |date=23 February 2007 |title=GE Announces Advancement in Incandescent Technology; New High-Efficiency Lamps Targeted for Market by 2010 |url=http://www.businesswire.com/portal/site/ge/index.jsp?ndmViewId=news_view&newsId=20070223005120 |publisher=[[Business Wire]] |url-status=dead |archive-url=https://web.archive.org/web/20130516151220/http://www.businesswire.com/portal/site/ge/index.jsp?ndmViewId=news_view&newsId=20070223005120 |archive-date=16 May 2013}}</ref> The HEI program was terminated in 2008 due to slow progress.<ref>{{cite news |last=Hamilton |first=Tyler |title=Why the brightest idea needs tinkering |url=https://www.thestar.com/business/2009/04/22/why_the_brightest_idea_needs_tinkering.html|newspaper=[[Toronto Star]] |date=22 April 2009 |url-status=live |archive-url=https://web.archive.org/web/20130620083715/http://www.thestar.com/business/2009/04/22/why_the_brightest_idea_needs_tinkering.html|archive-date=20 June 2013}}</ref><ref>{{cite news |last=Rahim |first=Saqib |date=28 June 2010 |title=The Incandescent Bulb Heads Offstage After Century-Long Performance |url=https://www.nytimes.com/cwire/2010/06/28/28climatewire-the-incandescent-bulb-heads-offstage-after-c-11795.html |work=The New York Times |url-status=live |archive-url=https://web.archive.org/web/20130518150756/http://www.nytimes.com/cwire/2010/06/28/28climatewire-the-incandescent-bulb-heads-offstage-after-c-11795.html |archive-date=18 May 2013}}</ref>
US Department of Energy research at [[Sandia National Laboratories]] initially indicated the potential for dramatically improved efficiency from a [[photonic lattice]] filament.<ref name=notsodim/> However, later work indicated that initially promising results were in error.<ref>{{cite web |title=Revolutionary tungsten photonic crystal could provide more power for electrical devices |url=https://share.sandia.gov/news/resources/releases/2003/other/planck-lin.html |publisher=[[Sandia National Laboratories]] |date=7 July 2003 |url-status=live |archive-url=https://web.archive.org/web/20130221204348/https://share.sandia.gov/news/resources/releases/2003/other/planck-lin.html |archive-date=21 February 2013}}</ref>

Prompted by legislation in various countries mandating increased bulb efficiency, ''hybrid'' incandescent bulbs have been introduced by [[Philips]]. The ''Halogena Energy Saver'' incandescents can produce about 23&nbsp;lm/W; about 30 percent more efficient than traditional incandescents, by using a reflective capsule to reflect formerly wasted infrared radiation back to the filament from which some is re-emitted as visible light.<ref name=NYT/> This concept was pioneered by Duro-Test in 1980 with a commercial product that produced 29.8&nbsp;lm/W.<ref>{{Cite journal |url=http://americanhistory.si.edu/collections/search/object/nmah_995209 |title=Prototype Heat-Mirror Tungsten Lamp |journal=Smithsonian Museum of American History |url-status=live |archive-url=https://web.archive.org/web/20151223061442/http://americanhistory.si.edu/collections/search/object/nmah_995209 |archive-date=23 December 2015}}</ref><ref>{{cite report|title=Energy Efficient Incandescent Lamp: Final Report |publisher=Lawrence Berkeley National Laboratory |date=April 1982}}</ref> More advanced reflectors based on [[interference filter]]s or [[photonic crystal]]s can theoretically result in higher efficiency, up to a limit of about 270&nbsp;lm/W (40% of the maximum efficacy possible).<ref name=Ilic>{{cite journal |title=Tailoring high-temperature radiation and the resurrection of the incandescent source |first1=Ognjen |last1=Ilic |journal=Nature Nanotechnology |volume=11 |issue=4 |pages=320–4 |year=2016 |doi=10.1038/nnano.2015.309 |pmid=26751172 |bibcode=2016NatNa..11..320I |hdl=1721.1/109242 |osti=1371442 |url=https://dspace.mit.edu/bitstream/1721.1/109242/1/Chen_Tailoring%20high-temperature.pdf |hdl-access=free |access-date=23 September 2019 |archive-date=14 February 2022 |archive-url=https://web.archive.org/web/20220214220607/https://dspace.mit.edu/bitstream/handle/1721.1/109242/Chen_Tailoring |url-status=live }}</ref> Laboratory proof-of-concept experiments have produced as much as 45&nbsp;lm/W, approaching the efficacy of compact fluorescent bulbs.<ref name=Ilic/><ref>{{cite news |last=McGrath |first=Matt |date=12 January 2016 |url=https://www.bbc.com/news/science-environment-35284112 |title=New development could lead to more effective lightbulbs |work=BBC News |url-status=live |archive-url=https://web.archive.org/web/20160113031746/http://www.bbc.com/news/science-environment-35284112 |archive-date=13 January 2016}}</ref>