Recently, a corporate client asked me to specify only LED fixtures with a lifetime of 100,000 hours, and preferred fixtures with a life of 200,000 hours. \u00a0I don’t know where they came up with these numbers, but my reply was that\u00a0an L70 of 100,000 hours or more cannot be validated through standard testing procedures. \u00a0Here’s why.<\/p>\n
To begin with, LEDs themselves don’t experience catastrophic failure the way incandescent and fluorescent lamps do. The don’t stop making light, but their output declines over time. \u00a0Today the generally accepted calculation of the life of an LED is called L70, which is the length of time before the light output has fallen to 70% of initial output.<\/p>\n
The IES approved lifetime calculation method begins by collecting data using the procedure described in LM-80<\/a> (ANSI\/IES LM-80 Measuring Maintenance of Light Output Characteristics of Solid-State Light Sources<\/em>). Please note that LM-80 measures “LED packages, arrays, and modules” not fully fabricated fixtures, and there’s some dispute about whether or not testing bare modules is appropriate. \u00a0However, it does permit module manufacturers to test once and derive a lifetime, rather than every fixture manufacturer testing every fixture with every module they want to offer, which would be incredibly burdensome and expensive.<\/p>\n LM-80 requires a minimum collection time of 6,000 hours (250 days) but sets no upper limit. \u00a0If manufacturers want to use the data they’ve collected and project future performance they use the calculation procedure in TM-21<\/a> (ANSI\/IES TM-21 Projecting Long-Term Luminous, Photon, and Radiant Flux Maintenance of LED Light Sources<\/em>). \u00a0Importantly, TM-21 only permits data to be projected to six times the LM-80 data collection time period. \u00a0This is because of uncertainties involved with longer predictions (see PS-10-08 IES Position on LED Product Lifetime Prediction<\/em> at\u00a0https:\/\/www.ies.org\/advocacy\/position-statements\/ps-10-18-ies-position-on-led-product-lifetime-prediction\/<\/a>). \u00a0So, an L70 of 50,000 hours is based on at least 8,333 hours of LM-80 testing. \u00a0That’s 347 days.<\/p>\n Thus, to say that an LED has an L70 100,000 hour life would require a data collection period of 16,667 hours (695 days), or 1,390 days (3.8 years of continuous testing) for a life of 200,000 hours. \u00a0Today, no LED manufacturer conducts LM-80 tests for that extended period of time because the lifetime of a given LED product is too short. \u00a0By the time you’ve finished a 4 year long test, the LED being tested is out of production and replaced by something new. \u00a0In the future, when the LED industry has matured and we’re no longer seeing continuous improvements in efficacy, color rendering, etc., they may test for that long, but not now.<\/p>\n Where do these 100,000 hour and longer lifetimes come from? \u00a0It seems that some manufacturers are using an internally generated prediction to get to these numbers. \u00a0The thing is, we don’t know what’s involved in that prediction, which means we can’t validate it or compare it to any other prediction. \u00a0We just have to take their word for it. With the LM-80\/TM-21 procedure, on the other hand, we know that testing labs, regardless of who or where, are using the same procedure and their results should be consistent and repeatable. \u00a0That allows us to reliably, confidently compare fixtures by any number of manufacturers.<\/p>\n","protected":false},"excerpt":{"rendered":" LED claims of 100,000 hour lifetimes can’t be validated. This post explains why.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[6,11],"tags":[76,74],"class_list":["post-2686","post","type-post","status-publish","format-standard","hentry","category-calculations","category-leds","tag-led-lifetime","tag-tm-21"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p4gZSw-Hk","jetpack_sharing_enabled":true,"jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":642,"url":"https:\/\/designinglight.com\/?p=642","url_meta":{"origin":2686,"position":0},"title":"Measuring and Reporting LED Life","author":"Jason Livingston","date":"May 31, 2016","format":false,"excerpt":"I\u2019m putting the finishing touches on a lighting design and as I look at cut sheets I continue to be disappointed that many fixture manufacturers still don\u2019t seem to understand the proper methods of measuring and reporting LED life. For example, an Edison Price cut sheet says that lamp life\u2026","rel":"","context":"In "Lamps"","block_context":{"text":"Lamps","link":"https:\/\/designinglight.com\/?cat=13"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":198,"url":"https:\/\/designinglight.com\/?p=198","url_meta":{"origin":2686,"position":1},"title":"New LED Performance Measurements","author":"Jason Livingston","date":"July 9, 2014","format":false,"excerpt":"The Illuminating Engineering Society (IES) has published two new documents related to measuring the performance of Light Emitting Diodes (LEDs).\u00a0 The titles, as well as the aspects that are included and excluded, reveal the complexity of LEDs. The basic problem is that LEDs typically do not fail the way other\u2026","rel":"","context":"In "LEDs"","block_context":{"text":"LEDs","link":"https:\/\/designinglight.com\/?cat=11"},"img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":360,"url":"https:\/\/designinglight.com\/?p=360","url_meta":{"origin":2686,"position":2},"title":"With LEDs, Knowledge is Power","author":"Jason Livingston","date":"March 29, 2015","format":false,"excerpt":"I\u2019ve been hired to review an architect\u2019s lighting design and then design an appropriate control system. The fixtures selected are all LED products by a manufacturer that falls into the high-end residential\/economy commercial range of quality and price. The cut sheets are extremely frustrating. After nearly a decade of LED\u2026","rel":"","context":"In "Design"","block_context":{"text":"Design","link":"https:\/\/designinglight.com\/?cat=18"},"img":{"alt_text":"\"CIExy1931 MacAdam\". Licensed under CC BY-SA 3.0 via Wikimedia Commons - http:\/\/commons.wikimedia.org\/wiki\/File:CIExy1931_MacAdam.png#\/media\/File:CIExy1931_MacAdam.png","src":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2015\/03\/CIExy1931_MacAdam-271x300.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":676,"url":"https:\/\/designinglight.com\/?p=676","url_meta":{"origin":2686,"position":3},"title":"How Bright Are Colored LEDs?","author":"Jason Livingston","date":"January 29, 2017","format":false,"excerpt":"Measuring and describing the brightness of colored LEDs is an increasingly important part of a lighting designer\u2019s practice. They are used more often, and in more types of projects, than ever before. Yet, we don\u2019t have an accurate method for understanding exactly how much light is being produced and how\u2026","rel":"","context":"In "Color"","block_context":{"text":"Color","link":"https:\/\/designinglight.com\/?cat=12"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/01\/VLambda.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/01\/VLambda.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2017\/01\/VLambda.png?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":4039,"url":"https:\/\/designinglight.com\/?p=4039","url_meta":{"origin":2686,"position":4},"title":"How are CCT and Duv Calculated? IES TM-40","author":"Jason Livingston","date":"September 30, 2024","format":false,"excerpt":"If you look up the definition of Correlated Color Temperature (CCT) in IES LS-1 you'll find, \"The absolute temperature of a blackbody whose chromaticity most nearly resembles that of the light source.\" \u00a0It seems straightforward. \u00a0The spectra of non-incandescent light sources don't exactly match a blackbody radiator. \u00a0They'll plot off\u2026","rel":"","context":"In "Color"","block_context":{"text":"Color","link":"https:\/\/designinglight.com\/?cat=12"},"img":{"alt_text":"C78.377 chromaticity quadrangles","src":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2024\/09\/3.8-C78.377-300x300.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":206,"url":"https:\/\/designinglight.com\/?p=206","url_meta":{"origin":2686,"position":5},"title":"Dimming That Doesn’t Dim Off","author":"Jason Livingston","date":"August 12, 2014","format":false,"excerpt":"Recently a designer specified 0-10V dimming for a series of LED downlights.\u00a0 The electrician powered the LEDs by connecting them to a nearby breaker panel.\u00a0 The 0-10V control signal was generated by the lighting control system.\u00a0 This was a simple system that should have worked with no problems.\u00a0 Much to\u2026","rel":"","context":"In "Controls"","block_context":{"text":"Controls","link":"https:\/\/designinglight.com\/?cat=9"},"img":{"alt_text":"Source: U.S. DOE","src":"https:\/\/i0.wp.com\/designinglight.com\/wp-content\/uploads\/2014\/08\/LED-dim-curves-1024x791.jpg?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]}],"_links":{"self":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/2686","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2686"}],"version-history":[{"count":2,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/2686\/revisions"}],"predecessor-version":[{"id":2692,"href":"https:\/\/designinglight.com\/index.php?rest_route=\/wp\/v2\/posts\/2686\/revisions\/2692"}],"wp:attachment":[{"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2686"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2686"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/designinglight.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2686"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}