Editing Electric light (section)

== Characteristics ==

=== Form factor ===
{{main|Incandescent light bulb#Bulb shapes|Lightbulb socket}}
Many lamp units, or light bulbs, are specified in standardized shape codes and socket names. Incandescent bulbs and their retrofit replacements are often specified as "[[A-series light bulb|A19]]/A60 [[Edison screw|E26]]/E27", a common size for those kinds of light bulbs. In this example, the "A" parameters describe the bulb size and shape within the [[A-series light bulb]] while the "E" parameters describe the [[Edison screw]] base size and thread characteristics.<ref>{{Cite web |title=Light Bulb Sizes, Shapes and Temperatures Charts – Bulb Reference Guide |url=https://www.superiorlighting.com/lighting-resources/light-bulb-learning-center/bulb-reference-guide/ |access-date=2022-10-07 |website=www.superiorlighting.com}}</ref>

=== Comparison parameters ===
Common comparison parameters include:<ref name="Bulbs.com 2012">{{cite web | title=Lighting Facts Labels – LED Lighting | website=Bulbs.com | date=2012-01-01 | url=https://www.bulbs.com/learning/lightingfacts.aspx | access-date=2023-04-10}}</ref>
* [[Luminous flux]] (in [[lumens]])
* [[Energy consumption]] (in [[watt]]s)
* [[Luminous efficacy]] (in lumens per watt)
* [[Color temperature]] (in [[kelvins]])
Less common parameters include [[color rendering index]] (CRI).

=== Life expectancy ===
Life expectancy for many types of lamp is defined as the number of hours of operation at which 50% of them fail, that is the [[median]] life of the lamps. Production tolerances as low as 1% can create a variance of 25% in lamp life, so in general some lamps will fail well before the rated life expectancy, and some will last much longer. For LEDs, lamp life is defined as the operation time at which 50% of lamps have experienced a 70% decrease in light output. In the 1900s the [[Phoebus cartel]] formed in an attempt to reduce the life of electric light bulbs, an example of [[planned obsolescence]].<ref>{{Cite news|url=https://www.newyorker.com/business/currency/the-l-e-d-quandary-why-theres-no-such-thing-as-built-to-last|title=The L.E.D. Quandary: Why There's No Such Thing as "Built to Last"|last=MacKinnon|first=J. B.|date=2016-07-14|magazine=The New Yorker|access-date=2017-11-05|issn=0028-792X|archive-url=https://web.archive.org/web/20171114154744/https://www.newyorker.com/business/currency/the-l-e-d-quandary-why-theres-no-such-thing-as-built-to-last|archive-date=2017-11-14|url-status=live}}</ref><ref>{{Cite web |date=2014-09-24 |title=The Great Lightbulb Conspiracy |url=https://spectrum.ieee.org/the-great-lightbulb-conspiracy |access-date=2022-10-07 |website=IEEE Spectrum |language=en}}</ref>

Some types of lamp are also sensitive to switching cycles. Rooms with frequent switching, such as bathrooms, can expect much shorter lamp life than what is printed on the box. Compact fluorescent lamps are particularly sensitive to switching cycles.<ref>{{Cite web |title=When to Turn Off Your Lights |url=https://www.energy.gov/energysaver/when-turn-your-lights |access-date=2023-03-06 |website=Energy.gov |language=en}}</ref>