FAQs on Market-Available LEDs
DOE's solid-state lighting (SSL) R&D program focuses on ensuring the development of energy-efficient SSL technologies, an emphasis that, without DOE leadership, might be lost on the path to commercialization. DOE has a responsibility to ensure that SSL reaches its full energy savings potential, significantly reducing building energy use and costs, and contributing to our nation's energy security.
This page answers some frequently asked questions about the status of light emitting diode (LED) and SSL technologies available on the market today.
Fact Sheets
LED Application Series: Recessed Downlights (PDF 650 KB)
Thermal Management of White LEDs (PDF 465KB)
Lifetime
of White LEDs (PDF 643 KB)
Energy Efficiency of White LEDs (PDF 937 KB)
Energy-Efficient
Lighting and Light-Emitting Diodes (PDF
1 MB)
Color
Quality of White LEDs (PDF 968 KB)
Why are we hearing so much about LEDs today?
LEDs have been around since the 1960s, but they are just now reaching the levels of luminous output and power that open the door to more applications. For example, today's commercially available LEDs offer energy efficiency, maintenance savings, impact resistance, durability, and other benefits for traffic signals, exit signs, and other specialty applications. White LEDs are approaching performance levels that make them attractive for use in automobiles, aircraft, and elevators. For most general illumination applications, however, current LEDs cannot yet compete with traditional sources on the basis of performance or cost. More research is needed to increase the efficiency and decrease the cost of LED technologies. How long will it take before we see energy-efficient, cost-competitive, white-light products on the market?
DOE's SSL R&D plan spans 20 years (2000-2020),
and includes three components: Core Technology Research, Product
Development, and Commercialization Support activities. The
good news is that tremendous progress is being made, faster
than originally anticipated. Researchers have already improved
the efficacy of white LEDs to approximately 50 lumens per watt,
almost four times more efficient than incandescent sources.
Costs are still high, but continue to drop significantly, from approximately
$250/kilo-lumen in 2004 to around $50/kilo-lumen in 2006 (based on manufacturer
estimates for volume purchase).
For comparison, conventional light sources (incandescent, fluorescent) cost
around $1/kilo-lumen.
There already appear to be a lot of white-light LED products available now. what should I look for?
Some of the LED products available today are marketed as "energy-efficient," but actually have very low light output compared to typical light sources. The combination of high price and low light output may actually make them a poor replacement for current technology. It is important to compare new LED products to the most efficient conventional technology (such as fluorescent, incandescent, or metal halide) that could be used in your specific application. The following checklist will help you determine if an LED product is right for your application:
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Ask how many watts
the product consumes and how many lumens of light
it produces. Lumens per
watt (lpw) is the commonly used measure of how efficiently
a light source is converting electricity into useable
light. For comparison, incandescent lamps typically
produce 12-15 lumens per watt of electric power. Compact
fluorescent lamps (CFLs) produce at least 50 lumens
per watt. Currently available high-brightness LEDs
can produce about 30-35 lumens per watt.
In task lighting applications, LEDs may be able to
provide enough light on the task, even though the total
lumens are less than comparable incandescent or fluorescent
sources. This is because LEDs emit light in a less
diffuse pattern than conventional light sources. In
contrast, standard incandescent bulbs and fluorescent
lamps emit light in all directions, and much of the
light output is absorbed inside the fixture or escapes
in an unintended direction. |
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Evaluate the cost. For comparison, a 75-watt incandescent
light bulb typically produces about 1,000 lumens and costs
less than $1. The problem is, it only lasts about 1,000
hours and only converts about 5% of the electricity it
consumes into light (the rest is wasted as heat). A comparable
CFL is 5 times more efficient, lasts 10,000 hours, and
costs less than $5. So the conventional light sources cost
around $1 per thousand lumens. Today's white LED products
cost more than $50 per thousand lumens. But that's only
part of the story. If you have lights that are on most
of the time, or in a hard-to-reach area, LEDs could save
significant maintenance and energy costs. |
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Assess the need for unique LED features. In some applications, the extra durability that LEDs can provide is worth a higher purchase price. Outdoor pathway and step lighting is an example of a sensible application for today's white LEDs. They provide a small amount of light right where it's needed, and can be powered by solar cells, eliminating the need for running wire outdoors. They are also good for applications where vibration typically leads to early failure of conventional light sources. Being a solid-state device, LEDs are highly resistant to damage caused by vibration. |
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Check the color of white LEDs. If you've ever
tried to match white paint, you know there are actually
many shades of white. There is a similar issue with lighting.
White light varies from “warm” or more
yellow/gold in appearance, to “cool” or
more blue. Today's white LEDs are typically “cooler” and
bluer, even compared to fluorescent sources. Further,
there is a trade-off between efficiency and color.
The “warmer” colored white LEDs provide
less light per watt of electricity consumed, compared
to the “cooler” white LEDs. |
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Get a sample of the product if possible, so you can evaluate
it yourself. Because of the current lack of
standardized testing procedures and product specifications
among LED product manufacturers, there is not yet a
reliable way to compare product performance based on
information provided by the manufacturer. The best
way to assess a product you are considering is to ask
for a sample. |
Do LEDs really last 50,000
hours? 100,000 hours?
There is no simple answer to this question. Considering that
100,000 hours is more than 11 years of 24/7 operation, it's
difficult to do life testing on these products! However,
SSL researchers have developed ways to estimate LED life,
based on shorter test periods. Unlike other light sources,
LEDs don't typically “burn out;” they simply
get dimmer over time. Although there is not yet an official
industry standard defining “life” of an LED,
the leading manufacturers report it as the point at which
light output has reached 70% of initial light output. Using
that definition, the best white LEDs have been found to have
a useful life of around 35,000 hours (that's four years of
continuous operation). LED lifetime is strongly dependent
on appropriate electrical and thermal design of the fixture
or system. While LEDs do not emit heat in the form of infrared
radiation (IR), they do generate conductive heat that must
be managed in order for the LED to maintain expected light
output. Reputable LED manufacturers provide detailed electrical
and thermal design specifications. When considering an LED-based
fixture or system, it may be worthwhile to ask about the
type of LEDs used and what provisions the product manufacturer
has made for heat management.
Why is there such variation
among available SSL products, in terms of efficacy and light
output?
There is currently a lack of consensus test procedures and
performance standards for LEDs. The performance of traditional
light sources (incandescent, fluorescent, HID) is determined
by accepted test procedures that are followed industry wide.
This allows comparison of products made by different manufacturers
because they all have to test their products and report results
in the same way. In many cases, test procedures will need
to be revised to account for technical differences in the
way LEDs operate, relative to traditional light sources.
DOE is working with the National Electrical Manufacturers
Association (NEMA), the Next Generation Lighting Industry
Alliance, and other industry and research organizations to
begin developing the needed metrics, codes, and standards
for SSL products.
How is DOE coordinating its R&D activities with the market?
The SSL Partnership between DOE and the Next Generation Lighting Industry Alliance is designed to enhance the manufacturing and commercialization focus of the DOE SSL R&D
program.
The Alliance is administered by NEMA, and its membership includes 3M, Acuity
Brands Lighting, Air Products & Chemicals Inc., CAO Group Inc., Color Kinetics
Inc., Corning Inc., Cree Inc., Dow Corning Corporation, Eastman Kodak Company,
GELcore LLC, General Electric Company, Lumileds Lighting LLC, OSRAM Opto Semiconductors
Inc., OSRAM Sylvania Inc., and Philips Electronics North America Corporation.
Learn more about the SSL Partnership and Next Generation Lighting Industry Alliance activities. In addition, DOE has developed a commercialization support strategy to ensure that its R&D investments lead to SSL technology commercialization. Working with the SSL Partnership and other industry and energy organizations, DOE is planning a full range of activities, including:
- ENERGY STAR® designation for SSL technologies and products
- Design competitions for lighting fixtures and systems using SSL
- Coordination with utility promotions and regional energy efficiency programs
- Technology procurement programs that encourage manufacturers to bring high-quality, energy-efficient SSL products to the market, and that link these products to volume buyers
- Consumer and business awareness programs
- Information resources for lighting design professionals and students
At the 2006 DOE SSL Workshop, DOE provided an update on
initial activities under way, including progress in the development
of ENERGY STAR criteria for SSL products, and the announcement
of a new SSL category in the 2006 Lighting for Tomorrow design
competition. For more information, see the 2006
SSL Workshop Highlights or
download specific workshop presentations
and materials. Are there ENERGY STAR SSL products on the market?
Not yet, although DOE's commercialization support strategy does include the development of an ENERGY STAR designation for SSL technologies and products. DOE will coordinate the timing of this process with SSL technology advances, to ensure optimal alignment of technology readiness and market readiness. |
