LED lamp
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top
using light-emitting diodes (LEDs). LED lamps are significantly more
energy-efficient than equivalent incandescent lamps and
lamps have efficiencies exceeding 200 lumens per watt (lm/W) and convert
have a lifespan several times longer than both incandescent and
fluorescent lamps.
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.cite-ref-6[6]
The LED lamp market is projected to grow from US$75.8 billion in 2020 to
US$160 billion in 2026.cite-ref-7[7] 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.cite-ref-8[8] Light output decreases
gradually over the lifetime of the LED.
Some LED lamps are drop-in replacements for incandescent or fluorescent
lamps. 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
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.
Contents
• History
• Plants
• See also
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History
Before the introduction of LED lamps, three types of lamps were used for
the bulk of general (white) lighting:
• Incandescent lights produce light with a glowing filament heated by
electric current.cite-ref-9[9] These are very inefficient, having a
luminous efficacy of 10–17 lm/W, and also have a short lifetime,
typically 1000 hours. They are being phased out of general lighting
applications. Incandescent lamps produce a continuous
black body spectrum of light similar to sunlight, and so produce high
Color rendering index (CRI).
two electrodes in a low pressure tube of mercury vapor, which is
converted to visible light by a fluorescent coating (phosphor) on the
inside of the tube. These are more efficient than incandescent lights,
having a luminous efficacy from 50 to 100 lm/W (depending on the
structure, type of phosphor and type of ballast used), have a longer
lifetime of 6,000–15,000 hours, and are widely used for residential and
office lighting. However, their mercury content makes them a hazard to
the environment, and they have to be disposed of as hazardous waste.
• Metal-halide lamps, which produce light by an arc between two
electrodes in an atmosphere of argon, mercury and other metals, and
iodine or bromine. These were among the most efficient white electric
lights before LEDs, having a luminous efficacy of 75–100 lm/W and a
relatively long bulb lifetime of 6,000–15,000 hours; because they
require a 5–7-minute warmup period before they reach full output,
metal-halides are not used for residential lighting, but for commercial
and industrial wide area lighting and, outdoors, for security lights and
streetlights. Like fluorescents, they also contain hazardous mercury.
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,cite-ref-andrews-10-0[10] which was developed under Howard C. Borden and Gerald
P. Pighini, and Monsanto Company's LED indicator lamp.cite-ref-andrews-10-1[10] 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.cite-ref-andrews-10-2[10]
The first high-brightness blue LED was demonstrated by Shuji Nakamura of
Nakamura were later awarded the 2014 Nobel Prize in Physics for the
invention of the blue LED.cite-ref-12[12] 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 lower frequencies, creating white light.cite-ref-13[13] New LED lights
entered the market near the start of the 21st century in the US (Cree)
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",cite-ref-l-prize-15-0[15]
challenging industry to develop replacements for 60 W incandescent lamps
and other lamps.cite-ref-16[16] 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
America became the first to submit lamps in the category to replace the
standard 60 W A-19 "Edison screw fixture" light bulb,cite-ref-1-18-0[18] 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.cite-ref-19[19]
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
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.
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.cite-ref-21[21] 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.cite-ref-22[22] Ushio released the first LED filament
followed by the world's first 60 W equivalent LED lamp in
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.cite-ref-29[29] 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.cite-ref-30[30] 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.cite-ref-31[31]
Examples of early adoption
In 2003, the first surgical goggles with LEDs were demonstrated.cite-ref-auto1-32-0[32]
Audi showed the Audi Nuvolari concept car with LED
daytime running lights and directionals, the 2004 Audi A8
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.cite-ref-auto2-33-1[33] In 2006, some
of the first LED spotlights for use in stores were released.cite-ref-39[39] In
2007, Audi was the first car manufacturer to offer headlights that
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
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.cite-ref-41[41]
In 2009, Audi was the first manufacturer to offer a car that exclusively
used LED lighting, the 2009 Audi R8.cite-ref-42[42] 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.cite-ref-43[43] In 2009 a new
highway (A29) was inaugurated in Aveiro, Portugal; it included the first
European public LED-based lighting highway.cite-ref-44[44]
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,cite-ref-45[45] and
many additional streetlight and municipal outdoor lighting projects soon
In 2016, the Indian government launched their Ujala LED bulb scheme,
with the goal of replacing all incandescent and CFL bulbs in the country
in favor of LED bulbs. According to Narendra Modi in March 2022, the
scheme had distributed 370 million LED bulbs free to households and
reduced power bills in middle class and poor households by ₹200 billion
(US$2.4 billion). The Ujala scheme also encouraged the expansion of
domestic LED production in India.cite-ref-48[48]
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 and
an LED are both semiconductor light sources, but laser diodes rely on
stimulated emission, whereas LEDs use spontaneous emission.
White light LEDs
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).
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.cite-ref-ledcri-49-0[49] Higher CRI values can be obtained using more
than three LED colors to cover a greater range of wavelengths.
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.cite-ref-ledcri-49-1[49] Following
successive increases in efficacy, which had reached 210 lm/W on a
production basis as of 2021, 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.cite-ref-philips-50-0[50]
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.cite-ref-51[51] For example, white LEDs of different color temperatures can
be combined to construct an LED bulb that decreases its color
temperature when dimmed.
LED drivers
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.cite-ref-auto-24-1[24] Very high power lamps
for industrial uses are frequently equipped with cooling fans.cite-ref-52[52] 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.cite-ref-53[53] 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
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
Early suspicions were that the LED droop was caused by elevated
temperatures. Scientists showed that temperature was not the root cause
of efficiency droop.cite-ref-58[58] The mechanism causing efficiency droop was
identified in 2007 as Auger recombination, which was taken with mixed
reaction.cite-ref-stevenson-57-1[57] A 2013 study conclusively identified Auger recombination
as the cause.cite-ref-59[59]
Some lasers have been adapted as an alternative to LEDs to provide
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 fashioncite-ref-62[62] (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.cite-ref-63[63]
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,cite-ref-65[65] 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.cite-ref-66[66]
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
LED lamps are made with standard lamp connections and shapes, such as an
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
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. 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.cite-ref-67[67]
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 lampscite-ref-68[68] 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
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%.cite-ref-71[71] 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.cite-ref-1-18-1[18]
Several companies offer LED lamps for general lighting purposes. The
technology is improving rapidly and new energy-efficient consumer LED
As of 2016, in the United States, LED lamps are close to being adopted
as the mainstream light sourcecite-ref-74[74] because of the falling prices and
because incandescent lamps are being phased out.cite-ref-75[75] 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.cite-ref-76[76] 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.cite-ref-77[77]
LED tube lamps
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
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.cite-ref-sabzalian-mohammad-r-2014-78-0[78] 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
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. 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.
Specialty
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
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.cite-ref-80[80] 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.cite-ref-81[81]
Ultra-Violet lamps
UV LEDs have grown rapidly in recent years because they can be set to
emit specific wavelengths of light. Unlike gas discharge or fluorescent
lamps, which are limited by their materials, LED wavelengths are
determined by the band gap width.
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.cite-ref-82[82]
Comparison with other lighting technologies
Comparison table
| | LED |
|---|---|
| | Philips ultra efficient (2023) |
| Purchase price | $7.19 |
| Watts | 4 |
| lumens (mean) | 840 |
| lumens/watt | 210 |
| Color temperature kelvin | 3000 |
| CRI | 80 |
| Lifespan (hours) | 50,000 |
| Bulb lifetime (years) @ 6 hours/day | 22.8 |
| Energy cost over 20 years @ 16.1 cents/… | $28 |
| Cost of bulbs over 20 years | $7 |
| Total cost over 20 years | $35 |
| Total cost per 860 lumens | $36 |
| Comparison based on 6 hours use per day… | |
| | | | |
|---|---|---|---|
| | EcoSmart clear (2018) | V-TAC (2018) | Philips (2017) |
| Purchase price | $3.29 | $1.79 | $2.54 |
| Watts | 6.5 | 9 | 8.5 |
| lumens (mean) | 800 | 806 | 800 |
| lumens/watt | 123.1 | 89.6 | 94.1 |
| Color temperature kelvin | 2700 | 2700 | 2700 |
| CRI | 80 | 80+ | 80 |
| Lifespan (hours) | 15,000 | 20,000 | 10,000 |
| Bulb lifetime (years) @ 6 hours/day | 6.8 | 9.1 | 4.6 |
| Energy cost over 20 years @ 16.1 cents/… | $46 | $63 | $60 |
| Cost of bulbs over 20 years | $10 | $5 | $13 |
| Total cost over 20 years | $56 | $69 | $73 |
| Total cost per 860 lumens | $60 | $73 | $78 |
| | | CFL | Halogen | Incandescent |
|---|---|---|---|---|
| | Cree (2019) | CFL | Halogen | Incandescent |
| Purchase price | $3.93 | $1.54 | $1.17 | $0.41 |
| Watts | 9.5 | 14 | 43 | 60 |
| lumens (mean) | 815 | 775 | 750 | 860 |
| lumens/watt | 85.8 | 55.4 | 17.4 | 14.3 |
| Color temperature kelvin | 2700 | 2700 | 2920 | 2700 |
| CRI | 85 | 82 | 100 | 100 |
| Lifespan (hours) | 25,000 | 10,000 | 1,000 | 1,000 |
| Bulb lifetime (years) @ 6 hours/day | 11.4 | 4.6 | 0.46 | 0.46 |
| Energy cost over 20 years @ 16.1 cents/… | $67 | $99 | $303 | $423 |
| Cost of bulbs over 20 years | $8 | $8 | $51 | $18 |
| Total cost over 20 years | $75 | $106 | $355 | $441 |
| Total cost per 860 lumens | $79 | $118 | $407 | $441 |
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.cite-ref-93[93] 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.cite-ref-94[94]
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 require 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
Energy Star qualification
Energy Star is an international standard for energy efficient consumer
generally use 20–30% less energy than required by US standards.cite-ref-99[99]
Energy Star LED qualifications:cite-ref-energystar-100-0[100]
• Reduces energy costs – uses at least 75% less energy than incandescent
lighting, saving on operating expenses.
• Reduces maintenance costs – lasts 35 to 50 times longer than
incandescent lighting and about 2 to 5 times longer than fluorescent
lighting. No lamp-replacements, no ladders, no ongoing disposal program.
• Reduces cooling costs – LEDs produce very little heat.
• Is guaranteed – comes with a minimum three-year warranty – far beyond
the industry standard.
• Offers convenient features – available with dimming on some indoor
models and automatic daylight shut-off and motion sensors on some
outdoor models.
• Is durable – will not break like a glass bulb.
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:
• Brightness is equal to or greater than existing lighting technologies
(incandescent or fluorescent) and light is well distributed over the
area lit by the fixture.
• Light output remains constant over time, only decreasing towards the
end of the rated lifetime (at least 35,000 hours or 12 annums based on
use of 8 hours per day).
• Excellent color quality. The shade of white light appears clear and
consistent over time.
• Efficiency is as good as or better than fluorescent lighting.
• Light comes on instantly when turned on.
• No flicker when dimmed.
• No off-state power draw. The fixture does not use power when it is
turned off, with the exception of external controls, whose power should
not exceed 0.5 watts in the off state.
• Power factor of at least 0.7 for all lamps of 5W or greater.
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.cite-ref-dimming-101-0[101]
Otherwise damage to the lamp and/or the dimmer may result. 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.cite-ref-102[102] LEDs with CRI below 75 are
not recommended for use in indoor lighting.cite-ref-103[103] 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.cite-ref-104[104]cite-ref-105[105]cite-ref-106[106] 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.cite-ref-107[107] 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.cite-ref-0-17-2[17]
white) while tungsten lamps are ~2,700K (yellow).cite-ref-111[111] 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
Some organizations recommend that people should not use bluish-white
lamps at night. The American Medical Association argues against using
bluish-white LEDs for municipal street lighting.cite-ref-115[115] Research suggests
that the shift to LED street lighting attracts 48% more flying insects
than HPS lamps, which could cause direct ecological impacts as well as
indirect impacts such as attracting more gypsy moths to port areas.cite-ref-116[116]
See also
References
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Further reading
• citerefe-fred-schubert2006E. Fred Schubert (2006). Light-Emitting Diodes. Cambridge University
Press. ISBN 978-1-139-45522-0.
• citerefkrigelberdugopicardlevy-boukris2016Krigel, A; Berdugo, M; Picard, E; Levy-Boukris, R; Jaadane, I; Jonet,
L; Dernigoghossian, M; Andrieu-Soler, C; Torriglia, A; Behar-Cohen, F
(2016). "Light-induced retinal damage using different light sources,
protocols and rat strains reveals LED phototoxicity" (PDF).
27751961. S2CID 1619530.
External links
Wikimedia Commons has media related to
LED lamps
.
• e-lumen.eu – a website from the European Commission about the second
generation of energy-saving lamps (archived 12 December 2009)
• Some cities are taking another look at LED lighting after AMA warning
(25 September 2016) – The Washington Post