LED lamp

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LED lamp
Led-lampa.jpg
A 230-volt LED lamp with an E27 base (10 watts, 806 lumens, 3000 Kelvins)
Type Light-emitting diode, light bulb
First production 1968;56 years ago (1968)
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines. LEDfilamentLightBulbE27.jpg
A 230-volt LED filament lamp, with an E27 base. The filaments are visible as the eight yellow vertical lines.
An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications LED bulbs.jpg
An assortment of LED lamps commercially available in 2010: floodlight fixtures (left), reading light (center), household lamps (center right and bottom), and low-power accent light (right) applications
An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally bonded to the heat sink Chip-On-Board COB LED Module.JPG
An 80W Chips on board (COB) LED module from an industrial light luminaire, thermally bonded to the heat sink

An LED lamp or LED light [1] is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps and fluorescent lamps. [2] [3] [4] The most efficient commercially available LED lamps have efficiencies exceeding 200 lumens per watt (lm/W) and convert more than half the input power into light. [5] [6] [7] Commercial LED lamps have a lifespan several times longer than both incandescent and fluorescent lamps. [8]

Contents

LED lamps require an electronic LED circuit to operate from mains power lines, and losses from this circuit means that the efficiency of the lamp is lower than the efficiency of the LED chips it uses. The driver circuit may require special features to be compatible with lamp dimmers intended for use on incandescent lamps. Generally the current waveform contains some amount of distortion, depending on the luminaires' technology. [9]

LEDs come to full brightness immediately with no warm-up delay. Frequent switching on and off does not reduce life expectancy as with fluorescent lighting. [10] Light output decreases gradually over the lifetime of the LED. [11] Some LED lamps are drop-in replacements for incandescent or fluorescent lamps. [12] LED lamps may use multiple LED packages for improved light dispersal, heat dissipation, and overall cost.

The text on retail LED lamp packaging may show the light output in lumens, the power consumption in watts, the color temperature in kelvins or a color description such as "warm white", "cool white" or "daylight", the operating temperature range, whether the lamp is dimmer compatible, whether the lamp is suitable for humid/damp/wet conditions, and sometimes the equivalent wattage of an incandescent lamp delivering the same output in lumens.

History

Illustration of Haitz's law, showing improvement in light output per LED over time, with a logarithmic scale on the vertical axis Haitz-law.svg
Illustration of Haitz's law, showing improvement in light output per LED over time, with a logarithmic scale on the vertical axis

Before the introduction of LED lamps, three types of lamps were used for the bulk of general (white) lighting:

Considered as energy converters, all these existing lamps are inefficient, emitting more of their input energy as waste heat than as visible light. Global electric lighting in 1997 consumed 2016 terawatthours of energy. Lighting consumes roughly 12% of electrical energy produced by industrialized countries. New technological developments in light-emitting semiconductors, combined with the huge markets for displays and area lighting, encouraged the development of more energy-efficient electric lights.

The first low-powered LEDs were developed in the early 1960s, and only produced light in the low, red frequencies of the spectrum. In 1968, the first commercial LED lamps were introduced: Hewlett-Packard's LED display, [13] which was developed under Howard C. Borden and Gerald P. Pighini, and Monsanto Company's LED indicator lamp. [13] However, early LED lamps were inefficient and could only display deep red colors, making them unsuitable for general lighting and restricting their usage to numeric displays and indicator lights. [13]

The first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation in 1994. [14] Isamu Akasaki, Hiroshi Amano and Nakamura were later awarded the 2014 Nobel Prize in Physics for the invention of the blue LED. [15] The existence of blue LEDs and high-efficiency LEDs led to the development of the first 'white LED', which employed a phosphor coating to partially convert the emitted blue light to red and green frequencies, creating a light that appears white. [16]

New LED lights entered the market near the start of the 21st century in the US (Cree) and Japan (Nichia, Panasonic, and Toshiba), and then starting in 2004 in Korea and China (Samsung, Kingsun, Solstice, Hoyol, and others.) [17]

In the US, the Energy Independence and Security Act (EISA) of 2007 authorized the Department of Energy (DOE) to establish the Bright Tomorrow Lighting Prize competition, known as the "L Prize", [18] challenging industry to develop replacements for 60 W incandescent lamps and other lamps. [19] Products meeting the competition requirements would use just 17% of the energy used by most incandescent lamps of that time.

Philips Lighting ceased research on compact fluorescents in 2008 and began devoting the bulk of its research and development budget to solid-state lighting. [20] On 24 September 2009, Philips Lighting North America became the first to submit lamps in the category to replace the standard 60 W A-19 "Edison screw fixture" light bulb, [21] with a design based on their earlier "AmbientLED" consumer product. DOE awarded Philips the prize after 18 months of extensive testing. Many other similarly efficient products followed. [22]

Early LED lamps varied greatly in chromaticity from the incandescent lamps they were replacing. A standard was developed, ANSI C78.377-2008, that specified the recommended color ranges for solid-state lighting products using cool to warm white LEDs with various correlated color temperatures. [23] In June 2008, NIST announced the first two standards for solid-state lighting in the United States. These standards detail performance specifications for LED light sources and prescribe test methods for solid-state lighting products.

Also in 2008 in the United States and Canada, the Energy Star program began to label lamps that meet a set of standards for starting time, life expectancy, color, and consistency of performance. The intent of the program is to reduce consumer concerns due to variable quality of products, by providing transparency and standards for the labeling and usability of products available in the market. [24] Energy Star Certified Light Bulbs is a resource for finding and comparing Energy Star qualified lamps.

A similar program in the United Kingdom (run by the Energy Saving Trust) was launched to identify lighting products that meet energy conservation and performance guidelines. [25] Ushio released the first LED filament lamp in 2008. [26] Philips released its first LED lamp in 2009, [27] followed by the world's first 60 W equivalent LED lamp in 2010, [28] [29] [30] [31] and a 75 watt equivalent version in 2011. [32]

The Illuminating Engineering Society of North America (IESNA) in 2008 published a documentary standard LM-79, which describes the methods for testing solid-state lighting products for their light output (lumens), efficacy (lumens per watt) and chromaticity.

As of 2016, in the opinion of Noah Horowitz of the Natural Resources Defense Council, new standards proposed by the United States Department of Energy would likely mean most light bulbs used in the future would be LED. [33]

By 2019 electricity usage in the United States had decreased for at least five straight years, due in part to U.S. electricity consumers replacing incandescent light bulbs with LEDs due to their energy efficiency and high performance. [34]

In 2023 Signify N.V. introduced the highly efficient LED lamps with EU efficiency class A, which requires an efficiency of at least 210 lm/W. [35]

Examples of early adoption

LEDs as Christmas illumination in Viborg, Denmark Sct Mathias xmas illumination 2010-12-14.jpg
LEDs as Christmas illumination in Viborg, Denmark

In 2003, the first surgical goggles with LEDs were demonstrated. [36] Audi showed the Audi Nuvolari concept car with LED headlights. [37] [38] [39]

In 2004, Audi released the first car with LED daytime running lights and directionals, the 2004 Audi A8 W12. [36] [40] [41]

In 2005, an LED lamp was installed to illuminate the Mona Lisa. [42] LEDs were in use at the Casino Breda in The Netherlands, the Vienna State Opera, and the venue for the Shanghai Grand Prix, for example. LED flashlights and headlamps for people were available. [37]

In 2006, some of the first LED spotlights for use in stores were released. [43]

In 2007, Audi was the first car manufacturer to offer headlights that solely used LEDs, used in the Audi R8. [44]

In 2008 Sentry Equipment Corporation in Oconomowoc, Wisconsin, US, was able to light its new factory interior and exterior almost solely with LEDs. Initial cost was three times that of a traditional mix of incandescent and fluorescent lamps, but the extra cost was recovered within two years via electricity savings, and the lamps should not need replacing for 20 years. [20] In 2009 the Manapakkam, Chennai office of the Indian IT company, iGate, spent ₹ 3,700,000 (US$ 80,000) to light 57,000 sq ft (5,300 m2) of office space with LEDs. The firm expected the new lighting to pay for itself within 5 years. [45]

In 2009, Audi was the first manufacturer to offer a car that exclusively used LED lighting, the 2009 Audi R8. [46]

In 2009 the exceptionally large Christmas tree standing in front of the Turku Cathedral in Finland was hung with 710 LED lamps, each using 2 watts. It has been calculated that these LED lamps paid for themselves in three and a half years, even though the lights run for only 48 days per year. [47]

In 2009 a new highway (A29) was inaugurated in Aveiro, Portugal; it included the first European public LED-based lighting highway. [48]

By 2010 mass installations of LED lighting for commercial and public uses were becoming common. LED lamps were used for a number of demonstration projects for outdoor lighting and LED street lights. The United States Department of Energy made several reports available on the results of many pilot projects for municipal outdoor lighting, [49] and many additional streetlight and municipal outdoor lighting projects soon followed. [50]

In 2016 Government of India launched 'Ujala LED bulb scheme' to lower India's carbon footprint and save electricity, it distributed 370 million LED bulbs free, by doing so as of March 2022, which resulted in saving of ₹200 billion (US$2.4 billion) of middle class and poor household power bill. The scheme is intended to replace all the incandescent and CFL light bulbs to more efficient LED lights in the nation. To lower the price of LED bulbs government encouraged light bulb production in the nation. [51]

Technology

LED lamps are often made with arrays of surface mount LED modules.

A significant difference from other light sources is that the light is more directional. An LED is a "Lambertian" emitter, producing a cone of light with half-power points about 60° from the axis. A laser diode is another form of LED emitter, but produces light by a different mechanism.

White light LEDs

LED lamp used in photography LED light (40979).jpg
LED lamp used in photography

General-purpose lighting requires a white light, emulating a black body at a specified temperature, from "warm white" (like an incandescent bulb) at 2700K, to "daylight" at around 6500K. The first LEDs emitted light in a very narrow band of wavelengths, of a color characteristic of the energy band gap of the semiconductor material used to make the LED. LEDs that emit white light are made using two principal methods: either mixing light from multiple LEDs of various colors, or using a phosphor to convert some of the light to other colors. The light is not the same as a true black body, giving a different appearance to colors than an incandescent bulb. Color rendering quality is specified by the color rendering index (CRI), and as of 2019 is about 80 for many LED bulbs, and over 95 for more expensive high-CRI LED lighting (100 is the ideal value).[ citation needed ]

RGB or trichromatic white LEDs use multiple LED chips emitting red, green, and blue wavelengths. These three colors combine to produce white light. The CRI is poor, typically 25 – 65, due to the narrow range of wavelengths emitted. [52] Higher CRI values can be obtained using more than three LED colors to cover a greater range of wavelengths.[ citation needed ]

The second method, the basis of most commercially available LED lamps, uses LEDs in conjunction with a phosphor to produce complementary colors from a single LED. Some of the light from the LED is absorbed by the molecules of the phosphor, causing them to fluoresce, emitting light of another color via the Stokes shift. The most common method is to combine a blue LED emitter with a yellow phosphor, producing a narrow range of blue wavelengths and a broad band of "yellow" wavelengths actually covering the spectrum from green to red. The CRI value can range from less than 70 to over 90, although a wide range of commercial LEDs of this type have a color rendering index around 82. [52] Following successive increases in efficacy, which had reached 210 lm/W on a production basis as of 2021, [53] this type has surpassed the performance of trichromatic LEDs. The phosphors used in white light LEDs can give correlated color temperatures in the range of 2,200 K (dimmed incandescent) up to 7,000 K or more. [54]

Color changing LED lighting

Tunable lighting systems employ banks of colored LEDs that can be individually controlled, either using separate banks of each color, or multi-chip LEDs with the colors combined and controlled at the chip level. [55] For example, white LEDs of different color temperatures can be combined to construct an LED bulb that decreases its color temperature when dimmed. [56]

LED drivers

Household LED lamp with its internal LED elements and LED driver circuitry exposed LED-E27-Light-Bulb-1134.jpg
Household LED lamp with its internal LED elements and LED driver circuitry exposed

LED chips require controlled direct current (DC) electrical power and an appropriate circuit as an LED driver is required to convert the alternating current from the power supply to the regulated voltage direct current used by the LEDs.

LED drivers are essential components of LED lamps to ensure acceptable lifetime and performance of the lamp. A driver can provide features such as dimming and remote control. LED drivers may be in the same lamp enclosure as the diode array, or remotely mounted from the light-emitting diodes. LED drivers may require additional components to meet regulations for acceptable AC line harmonic current.

Thermal management

LED lamps run cooler than their predecessors since there is no electric arc or tungsten filament, but they can still cause burns. Thermal management of high-power LEDs is required to keep the junction temperature of the LED device close to ambient temperature, since increased temperature reduces light output and can cause catastrophic failure. LEDs use much less power for a given light output, but they do produce some heat, and it is concentrated in a very small semiconductor die. Because of their low operating temperature, LED lamps cannot lose much heat via radiation; instead, heat is conducted through the back of the die to a suitably designed heat sink or cooling fin, from where it is dissipated via convection. [27] Very high power lamps for industrial uses are frequently equipped with cooling fans. [57] Some manufacturers place the LEDs and all circuitry in a glass bulb just like conventional incandescent bulbs, but with a helium gas filling to conduct heat and thus cool the LEDs. [58] Others place the LEDs on a circuit board with an aluminum backing; the aluminum back is connected thermally to the aluminum base of the lamp using thermal paste, and the base is embedded in a melamine plastic shell. Because of the need for convection cooling around an LED lamp, careful consideration is necessary when placing the lamp in an enclosed or poorly vented luminaire or close to thermal insulation.

Efficiency droop

Disassembled LED lamp with switched-mode power supply circuit board and Edison screw EcoEnergy EE-02-010.JPG
Disassembled LED lamp with switched-mode power supply circuit board and Edison screw
Efficiency droop in an InGaN LED as a function of its input current 20130501 Efficiency droop of InGaN LED vs injection current.svg
Efficiency droop in an InGaN LED as a function of its input current

The term "efficiency droop" refers to the decrease in luminous efficacy of LEDs as the electric current increases. Instead of increasing current levels, light output is usually increased by connecting multiple LED emitters in parallel and/or series in one lamp. Solving the problem of efficiency droop would mean that household LED lamps would require fewer LEDs, which would significantly reduce costs. [60] [61] [62] [63]

Early suspicions were that the LED droop was caused by elevated temperatures. Scientists showed that temperature was not the root cause of efficiency droop. [64] The mechanism causing efficiency droop was identified in 2007 as Auger recombination, which was taken with mixed reaction. [63] A 2013 study conclusively identified Auger recombination as the cause. [65]

Some lasers have been adapted as an alternative to LEDs to provide highly focused illumination. [66] [67]

Applications

LED lamps are used for both general and special-purpose lighting. Where colored light is needed, LEDs that inherently emit light of a single color require no energy-absorbing filters. LED lamps are commonly available as drop-in replacements for either bulbs or fixtures, replacing either an entire fixture (such as LED light panels replacing fluorescent troffers or LED spotlight fixtures replacing similar halogen fixtures) or bulbs (such as LED tubes replacing fluorescent tubes inside troffers or LED HID replacement lamps replacing HID bulbs inside HID fixtures) The differences between replacing a fixture and replacing a bulb are that, when a fixture (like a troffer) is replaced with something like an LED panel, the panel must be replaced in its entirety if the LEDs or the driver it contains fail since it is impossible to replace them individually in a practical fashion [68] (although the driver is often separate and so it may be replaced), where as, if only the bulb is replaced with an LED replacement lamp, the lamp can be replaced independently of the fixture should the lamp fail. Some LED replacement lamps require the fixture to be modified such as by electrically removing the fixture's ballast, thus connecting the LED lamp directly to the mains supply; others can work without any modifications to the fixture. [69]

BAPS Shri Swaminarayan Mandir Atlanta illumination with color mixing LED fixtures DSC09917 BAPS Temple - E view by Volkan Yuksel.jpg
BAPS Shri Swaminarayan Mandir Atlanta illumination with color mixing LED fixtures
Computer-led LED lighting allows enhancement of unique qualities of paintings in the National Museum in Warsaw. Muzeum Narodowe w Warszawie Galeria Sztuki XIX wieku.JPG
Computer-led LED lighting allows enhancement of unique qualities of paintings in the National Museum in Warsaw.

White-light LED lamps have longer life expectancy and higher efficiency (more light for the same electricity) than most other lighting when used at the proper temperature. LED sources are compact, which gives flexibility in designing lighting fixtures and good control over the distribution of light with small reflectors or lenses. Because of the small size of LEDs, control of the spatial distribution of illumination is extremely flexible, [71] and the light output and spatial distribution of an LED array can be controlled with no efficiency loss.

LEDs using the color-mixing principle can emit a wide range of colors by changing the proportions of light generated in each primary color. This allows full color mixing in lamps with LEDs of different colors. [72] Unlike other lighting technologies, LED emission tends to be directional (or at least Lambertian), which can be either advantageous or disadvantageous, depending on requirements. For applications where non-directional light is required, either a diffuser is used, or multiple individual LED emitters are used to emit in different directions.

Household LED lamps

Sizes and bases

A selection of consumer LED lamps available in 2012 as drop-in replacements for incandescent bulbs in screw-type sockets LED bulbs 2012.jpg
A selection of consumer LED lamps available in 2012 as drop-in replacements for incandescent bulbs in screw-type sockets

LED lamps are made with standard lamp connections and shapes, such as an Edison screw base, an MR16 shape with a bi-pin base, or a GU5.3 (bi-pin cap) or GU10 (bayonet fitting) and are made compatible with the voltage supplied to the sockets. They include driver circuitry to rectify the AC power and convert the voltage to an appropriate value, usually a switched-mode power supply.

As of 2010 some LED lamps replaced higher wattage bulbs; for example, one manufacturer claimed a 16-watt LED lamp was as bright as a 150 W halogen lamp. [73] A standard general-purpose incandescent bulb emits light at an efficacy of about 14 to 17 lm/W depending on its size and voltage. (Efficacy of incandescent lamps designed for 230 V supplies is less, because the lower supply voltage in north America is more favorable to efficacy.) According to the European Union standard, an energy-efficient lamp that claims to be the equivalent of a 60 W tungsten lamp must have a minimum light output of 806 lumens. [74]

High-power LED "corn cob" lamp LED E27 corn.JPG
High-power LED "corn cob" lamp

Some models of LED lamps are compatible with dimmers. LED lamps often have directional light characteristics. The best of these lamps, as of 2022, are more power-efficient than compact fluorescent lamps [75] [ better source needed ] and offer lifespans of 30,000 or more hours, reduced if operated at a higher temperature than specified. Incandescent lamps have a typical life of 1,000 hours, [76] and compact fluorescents about 8,000 hours. [77] LED and fluorescent lamps both use phosphors, whose light output declines over their lifetimes. Energy Star specifications requires LED lamps to typically drop less than 10% after 6,000 or more hours of operation, and in the worst case not more than 15%. [78] LED lamps are available with a variety of color properties. The purchase price is higher than most other lamps –although dropping –but the higher efficiency usually makes total cost of ownership (purchase price plus cost of electricity and changing bulbs) lower. [21]

Several companies offer LED lamps for general lighting purposes. The technology is improving rapidly and new energy-efficient consumer LED lamps are available. [79] [80] As of 2016, in the United States, LED lamps are close to being adopted as the mainstream light source [81] because of the falling prices and because incandescent lamps are being phased out. [82] In the U.S. the Energy Independence and Security Act of 2007 effectively bans the manufacturing and importing of most current incandescent lamps. LED lamps have decreased substantially in price, and many varieties are sold with subsidized prices from local utilities. However, in September 2019 the Trump administration rolled back requirements for new, energy-efficient light bulbs. [83] The Biden administration finalized efficiency regulations in 2023 that require 45 lm/W lighting and will save consumers $3 billion per year in electricity costs. [84]

LED tube lamps

A 17 W tube of LEDs which has the same intensity as a 45 W fluorescent tube Fluo-45W LED-17W.jpg
A 17 W tube of LEDs which has the same intensity as a 45 W fluorescent tube

LED tube lights are designed to physically fit in fixtures intended for fluorescent tubes. Some LED tubular lamps are intended to be a drop-in replacement into existing fixtures if appropriate ballast is used. Others require rewiring of the fixtures to remove the ballast. An LED tube lamp generally uses many individual Surface-Mounted LEDs which are directional and require proper orientation during installation as opposed to Fluorescent tube lamps which emit light in all directions around the tube. Most LED tube lights available can be used in place of T5, T8, T10, or T12 tube designations, T8 is D26mm, T10 is D30mm, in lengths of 590 mm (23 in), 1,200 mm (47 in) and 1,500 mm (59 in).

Lighting designed for LEDs

LED-wall lamp Svetodiodnyi svetil'nik.jpg
LED-wall lamp

Newer light fittings with long-lived LEDs built-in, or designed for LED lamps, have been coming into use as the need for compatibility with existing fittings diminishes. Such lighting does not require each bulb to contain circuitry to operate from mains voltage.

Plants

Experiments revealed surprising performance and production of vegetables and ornamental plants under LED light sources. [85] Many plant species have been assessed in greenhouse trials to make sure that the quality of biomass and biochemical ingredients of such plants is at least comparable with those grown in field conditions. Plant performance of mint, basil, lentil, lettuce, cabbage, parsley and carrot was measured by assessing both the health and vigor of the plants and the success of the LEDs in promoting growth. Also noticed was profuse flowering of select ornamentals including primula, marigold and stock. [85] [86]

Light emitting diodes (LEDs) offer efficient electric lighting in desired wavelengths (red + blue) which support greenhouse production in minimum time and with high quality and quantity.[ citation needed ] As LEDs are cool, plants can be placed very close to light sources without overheating or scorching, requiring much less space for intense cultivation than with hot-running lighting.[ citation needed ]

Specialty

LED Flashlight replacement bulb (left), with tungsten equivalent (right) New torch bulb.jpg
LED Flashlight replacement bulb (left), with tungsten equivalent (right)

White LED lamps have achieved market dominance in applications where high efficiency is important at low power levels. Some of these applications include flashlights, solar-powered garden or walkway lights, and bicycle lights. Colored LED lamps are now commercially used for traffic signal lamps, where the ability to emit bright light of the required color is essential, and in strings of holiday lights. LED automotive lamps are widely used for their long life and small size. Multiple LEDs are used in applications where more light output than available from a single LED is required.

Outdoor lighting

LED floodlamps LED floodlights.jpg
LED floodlamps

By about 2010 LED technology came to dominate the outdoor lighting industry, as earlier LEDs were not bright enough for outdoor lighting. A study completed in 2014 concluded that color temperature and accuracy of LED lights was easily recognized by consumers, with preference towards LEDs at natural color temperatures. [87] LEDs are now able to match the brightness and warmer color temperature that consumers desire from their outdoor lighting system.

LEDs are increasingly used for street lighting in place of mercury and sodium lamps due to their lower running and lamp replacement costs. However, there have been concerns that the use of LED street lighting with predominantly blue light can cause eye damage, and that some LEDs switch on and off at twice mains frequency, causing malaise in some people, and possibly being misleading with rotating machinery due to stroboscopic effects. These concerns can be addressed by use of appropriate lighting, rather than simple concern with cost. [88]

Ultra-Violet lamps

UV LEDs have grown rapidly in recent years because they can be set to emit specific wavelengths of light [89] . Unlike gas discharge or fluorescent lamps, which are limited by their materials, LED wavelengths are determined by the band gap width. [90] For Vitamin D production, LED lamps are better because traditional lamps can’t produce the exact 293 nanometer wavelength needed to boost Vitamin D levels. UVB lamps at 293 nanometers are more effective than other UVB lamps (like 312 nanometer or broadband types) because they provide enough UVB light for Vitamin D without causing skin redness, even at lower doses. [91]

Comparison with other lighting technologies

See luminous efficacy for an efficiency chart comparing various technologies.

Comparison table

Cost comparison for 60 watt incandescent equivalent light bulb (U.S. residential electricity prices)
LED CFL [92] Halogen [93] Incan­descent [94]
Philips ultra
efficient (2023) [95] 		EcoSmart
clear (2018) [96] 		V-TAC
(2018) [97] 		Philips
(2017) [98] 		Cree
(2019) [99]
Purchase price$7.19$3.29$1.79$2.54$3.93$1.54$1.17$0.41
Watts46.598.59.5144360
lumens (mean)840800806800815775 [100] 750860
lumens/watt 210123.189.694.185.855.417.414.3
Color temperature kelvin30002700270027002700270029202700
CRI 808080+808582100100
Lifespan (hours)50,00015,00020,00010,00025,00010,0001,0001,000
Bulb lifetime (years) @ 6 hours/day22.86.89.14.611.44.60.460.46
Energy cost over 20 years @ 16.1 cents/kWh [101] $28$46$63$60$67$99$303$423
Cost of bulbs over 20 years$7$10$5$13$8$8$51$18
Total cost over 20 years$35$56$69$73$75$106$355$441
Total cost per 860 lumens$36$60$73$78$79$118$407$441
Comparison based on 6 hours use per day (43,800 hours over 20 yrs)

In keeping with the long life claimed for LED lamps, long warranties are offered. However, currently there are no standardized testing procedures set by the Department of Energy in the United States to prove these assertions by each manufacturer. [102] A typical domestic LED lamp is stated to have an "average life" of 15,000 hours (15 years at 3 hours/day), and to support 50,000 switch cycles. [103]

Incandescent and halogen lamps naturally have a power factor of 1, but Compact fluorescent and LED lamps use input rectifiers and this causes lower power factors. Low power factors can result in surcharges for commercial energy users; CFL and LED lamps are available with driver circuits to provide any desired power factor, or site-wide power factor correction can be performed. EU standards requires a power factor better than 0.4 for lamp powers between 2 and 5 watts, better than 0.5 for lamp powers between 5 and 25 watts and above 0.9 for higher power lamps. [104] [105]

Energy Star qualification

Energy Star is an international standard for energy efficient consumer products. [106] [107] Devices carrying the Energy Star service mark generally use 20–30% less energy than required by US standards. [108]

Energy Star LED qualifications: [109]

To qualify for Energy Star certification, LED lighting products must pass a variety of tests to prove that the products will display the following characteristics:

Limitations

LED emitters are inherently suitable for dimming, because they can operate over a wide range of currents without significant change of color. However, the circuits in LED lamps must be explicitly designed to be dimmable and compatible with particular types of dimmer switch. [110] Otherwise damage to the lamp and/or the dimmer may result.

Variable color temperature LED array in a floodlamp Led Lights Panel.jpg
Variable color temperature LED array in a floodlamp

Color rendering is not identical to that of incandescent lamps, which emit close to perfect black-body radiation, as does the sun. A measurement unit called CRI is used to record how a light source renders eight color sample chips, on a scale from 0 to 100. [111] LEDs with CRI below 75 are not recommended for use in indoor lighting. [112]

Badly designed LED lamps may flicker. The effect can be seen on a slow motion video of such a lamp. The extent of flicker is based on the quality of the DC power supply built into the lamp structure, usually located in the lamp base. Longer exposures to flickering light contribute to headaches and eye strain. [113] [114] [115]

LED life span as a function of lumen maintenance drops at higher temperatures. Thermal management of high-power LEDs is a significant factor in design of solid state lighting equipment. LED lamps are sensitive to excessive heat, like most solid state electronic components. Also, the presence of incompatible volatile organic compounds can impair the performance and reduce lifetime. [116] The long life of LEDs, expected to be about 50 times that of the most common incandescent lamps and significantly longer than fluorescent types, is advantageous for users but will affect manufacturers as it reduces the market for replacements in the distant future. [20]

The human circadian rhythm can be affected by light sources. [117] [118] The effective color temperature of daylight is ~5,700K [119] (bluish white) while tungsten lamps are ~2,700K (yellow). [120] People who have circadian rhythm sleep disorders are sometimes treated with light therapy (exposure to intense bluish white light during the day) and dark therapy (wearing amber-tinted goggles at night to reduce bluish light). [121] [122] [123]

Some organizations recommend that people should not use bluish-white lamps at night. [124] The American Medical Association argues against using bluish-white LEDs for municipal street lighting. [125] [126] [127] Research suggests that the shift to LED street lighting attracts 48% more flying insects than HPS lamps [128] , which could cause direct ecological impacts as well as indirect impacts such as attracting more gypsy moths to port areas. [129]

See also

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A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor coating in the lamp glow. Fluorescent lamps convert electrical energy into useful light much more efficiently than incandescent lamps, but are less efficient than most LED lamps. The typical luminous efficacy of fluorescent lamps is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output.

<span class="mw-page-title-main">Lighting</span> Deliberate use of light to achieve practical or aesthetic effects

Lighting or illumination is the deliberate use of light to achieve practical or aesthetic effects. Lighting includes the use of both artificial light sources like lamps and light fixtures, as well as natural illumination by capturing daylight. Daylighting is sometimes used as the main source of light during daytime in buildings. This can save energy in place of using artificial lighting, which represents a major component of energy consumption in buildings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants.

<span class="mw-page-title-main">Flashlight</span> Portable hand-held electric light

A flashlight or electric torch, usually shortened to torch, is a portable hand-held electric lamp. Formerly, the light source typically was a miniature incandescent light bulb, but these have been displaced by light-emitting diodes (LEDs) since the early 2000s. A typical flashlight consists of the light source mounted in a reflector, a transparent cover to protect the light source and reflector, a battery, and a switch, all enclosed in a case.

<span class="mw-page-title-main">High-intensity discharge lamp</span> Type of electric lamp/bulb

High-intensity discharge lamps are a type of electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with noble gas and often also contains suitable metal or metal salts. The noble gas enables the arc's initial strike. Once the arc is started, it heats and evaporates the metallic admixture. Its presence in the arc plasma greatly increases the intensity of visible light produced by the arc for a given power input, as the metals have many emission spectral lines in the visible part of the spectrum. High-intensity discharge lamps are a type of arc lamp.

<span class="mw-page-title-main">Mercury-vapor lamp</span> Light source using an electric arc through mercury vapor

A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger soda lime or borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from the ultraviolet radiation the light produces, and a convenient mounting for the fused quartz arc tube.

<span class="mw-page-title-main">Compact fluorescent lamp</span> Fluorescent lamps with folded tubes, often with built-in ballast

A compact fluorescent lamp (CFL), also called compact fluorescent light, energy-saving light and compact fluorescent tube, is a fluorescent lamp designed to replace an incandescent light bulb; some types fit into light fixtures designed for incandescent bulbs. The lamps use a tube that is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp.

<span class="mw-page-title-main">Induction lamp</span> Gas-discharge lamp using electric and magnetic fields to transfer energy to the gas inside

The induction lamp, electrodeless lamp, or electrodeless induction lamp is a gas-discharge lamp in which an electric or magnetic field transfers the power required to generate light from outside the lamp envelope to the gas inside. This is in contrast to a typical gas discharge lamp that uses internal electrodes connected to the power supply by conductors that pass through the lamp envelope. Eliminating the internal electrodes provides two advantages:

<span class="mw-page-title-main">Architectural lighting design</span> Field within architecture, interior design and electrical engineering

Architectural lighting design is a field of work or study that is concerned with the design of lighting systems within the built environment, both interior and exterior. It can include manipulation and design of both daylight and electric light or both, to serve human needs.

<span class="mw-page-title-main">Multifaceted reflector</span> Light bulb

A multifaceted reflector light bulb is a reflector housing format for halogen as well as some LED and fluorescent lamps. MR lamps were originally designed for use in slide projectors, but see use in residential lighting and retail lighting as well. They are suited to applications that require directional lighting such as track lighting, recessed ceiling lights, desk lamps, pendant fixtures, landscape lighting, retail display lighting, and bicycle headlights. MR lamps are designated by symbols such as MR16 where the diameter is represented by numerals indicating units of eighths of an inch. Common sizes for general lighting are MR11 and MR16, with MR8 and MR20 used in specialty applications. Many run on low voltage rather than mains voltage alternating current so require a power supply.

<span class="mw-page-title-main">Grow light</span> Lighting to aid plant growth

A grow light is an electric light that can help plants grow. Grow lights either attempt to provide a light spectrum similar to that of the sun, or to provide a spectrum that is more tailored to the needs of the plants being cultivated. Outdoor conditions are mimicked with varying colour temperatures and spectral outputs from the grow light, as well as varying the intensity of the lamps. Depending on the type of plant being cultivated, the stage of cultivation, and the photoperiod required by the plants, specific ranges of spectrum, luminous efficacy and color temperature are desirable for use with specific plants and time periods.

<span class="mw-page-title-main">Phase-out of incandescent light bulbs</span> For more energy-efficient alternatives

Various governments have passed legislation to phase out manufacturing or importation of incandescent light bulbs for general lighting in favor of more energy-efficient alternatives. The regulations are generally based on efficiency, rather than use of incandescent technology.

<span class="mw-page-title-main">LED street light</span> Type of lighting fixture

An LED street light or road light is an integrated light-emitting diode (LED) light fixture that is used for street lighting.

Electron-stimulated luminescence (ESL) is production of light by cathodoluminescence, i.e. by a beam of electrons made to hit a fluorescent phosphor surface. This is also the method used to produce light in a cathode ray tube (CRT). Experimental light bulbs that were made using this technology do not include magnetic or electrostatic means to deflect the electron beam.

<span class="mw-page-title-main">Fluorescent-lamp formats</span> Types of lamp

Since their introduction as a commercial product in 1939, many different types of fluorescent lamp have been introduced. Systematic nomenclature identifies mass-market lamps as to overall shape, power rating, length, color, and other electrical and illuminating characteristics.

United States Lighting Energy Policy is moving towards increased efficiency in order to lower greenhouse gas emissions and energy use. Lighting efficiency improvements in the United States can be seen through different standards and acts. The Energy Independence and Security Act of 2007 laid out changes in lighting legislation for the United States. This set up performance standards and the phase-out of incandescent light bulbs in order to require the use of more efficient fluorescent lighting. EISA 2007 is an effort to increase lighting efficiency by 25-30%. Opposition to EISA 2007 is demonstrated by the Better Use of Light Bulbs Act and the Light Bulb Freedom of Choice Act. The efforts to increase lighting efficiency are also demonstrated by the Energy Star program and the increase efficiency goals by 2011 and 2013. A ban on the manufacture and sale of most general purpose incandescent bulbs in the U.S. took effect on August 1, 2023.

<span class="mw-page-title-main">High-CRI LED lighting</span> LED lighting source

High-CRI LED lighting is a light-emitting diode (LED) lighting source that offers a high color rendering index (CRI).

<span class="mw-page-title-main">LED filament</span>

A LED filament light bulb is a LED lamp which is designed to resemble a traditional incandescent light bulb with visible filaments for aesthetic and light distribution purposes, but with the high efficiency of light-emitting diodes (LEDs). The name comes from their strings of many close-spaced series-connected diodes, which resemble the filaments of incandescent light bulbs much closer than previous bulbs with many LEDs. They are made as direct replacements for conventional incandescent bulbs, as they are made in the same shapes, they use the same bases that fit the same sockets, and they work at the same supply voltage. They may be used for their appearance, similar when lit to a clear incandescent bulb, or for their wide angle of light distribution, typically 300°. They are also more efficient than many other LED lamps.

Light-emitting diodes (LEDs) produce light by the recombination of electrons and electron holes in a semiconductor, a process called "electroluminescence". The wavelength of the light produced depends on the energy band gap of the semiconductors used. Since these materials have a high index of refraction, design features of the devices such as special optical coatings and die shape are required to efficiently emit light. A LED is a long-lived light source, but certain mechanisms can cause slow loss of efficiency of the device or sudden failure. The wavelength of the light emitted is a function of the band gap of the semiconductor material used; materials such as gallium arsenide, and others, with various trace doping elements, are used to produce different colors of light. Another type of LED uses a quantum dot which can have its properties and wavelength adjusted by its size. Light-emitting diodes are widely used in indicator and display functions, and white LEDs are displacing other technologies for general illumination purposes.

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