31 October 2013 – Light emitting diode, or LED, products are rapidly becoming useful alternatives to traditional light sources, but buyers need to do their homework before investing in them because few have undergone rigorous testing in real-life settings over a prolonged period of time, due to their comparatively early stage of development.
There is also a wide variation in product quality and how effectively they may light a space. Some lower quality LEDs may provide insufficient light, flicker when dimmed, change colour through life or fail prematurely.
An LED is a form of solid state lighting that uses use a semi-conductor instead of filaments, plasma or gas. It is not only highly energy efficient, but provides excellent illumination in a wide range of applications. It lasts up to 50 times longer than incandescent lamps and two to five times longer than fluorescent lamps, making it ideal for hard-to-access locations.
LEDs are also durable and can withstand vibration and shocks; are not affected by regular on-off switching, and are at full brightness as soon as they are switched. Many are fully dimmable.
To ensure you are buying a quality LED product the following performance indicators should be checked:
Be cautious of claims that lamps are equivalent to common incandescent or halogen reflector lamps. The best LEDs are about four to five times more efficient than their typical incandescent lamp equivalent. For an LED lamp claiming to produce as much light as a 60W incandescent or 50W dichroic reflector lamp, it will need to use at least 12W of energy. Look for sensible numbers on any claim of equivalence and compare products.
Look for information about the light output, measured in lumens (lm). Lumens are the best, most accurate way to compare two different types of lighting. The higher the number of lumens, the more light is emitted. If the lamp carries a lumen output rating, it may also indicate that it was actually tested for this performance. The following table shows the number of lumens that a range of traditional incandescent light bulbs produces. An LED with the same number of lumens as one of the lamps in the table should have a similar light output:
|Incandescent (GLS) lamp||Light output in lumens|
For a LED lamp to provide equivalent light to the common 50W MR-16 dichroic downlight, it must produce a minimum of 480 lumens. To achieve light output equivalent to the best quality MR-16 downlights, it will emit 900 lumens.
Information on some LED packaging is not always accurate. Sometimes the information on light output will relate to the light source – that is, the LED chip, not the light fixture (luminaire), of which the chip is only one component. LED light sources tested under laboratory conditions will always have a higher light output than the LED lamp when used in normal conditions. The most useful measure is when light output from the complete light fixture is measured.
Lamp lifetime, in hours
Some LEDs claim to have very long rated life, 60,000 hours or more – having been tested, but under the best laboratory conditions. For high quality LED products, the expected (and more believable) lifetime is somewhere in the range of 20,000 to 40,000 hours. It is very likely the claimed LED life is not based on testing for the indicated life. Rather, life can be based on a minimum 6000 hours operation and then a prediction of the light output decay is used to determine operational lifetime. Look for a realistic lifetime and manufacturers who can back up their lifetime claims, either with testing or certification indicated on the product packaging.
Lamp warranty period. A good approximation for information on lifetime testing is the warranty period that a manufacturer is willing to provide. For a lamp claiming to last 25,000 hours (about 34 months of continuous operation, or 22 years of regular nightly use in a home), a manufacturer should be able to provide a warranty of at least two to three years. If a longer life time is claimed, look for a corresponding longer warranty of perhaps five years.
Colour temperature. LEDs are a coloured light source and are designed to produce white light using a number of methods. As a result, they produce white light in a number of “shades” – just like incandescent and fluorescent lamps – from warm-white (similar to a regular, incandescent lamp) to cool white or bluish white, to simulate daylight. Look for the colour that best suits the intended application.
Colour Rendering Index
Some LEDs are better at helping the human eye discern colours than others, depending on the method used to produce white light. Look for lamps that have a Colour Rendering Index, or CRI, of at least 65 for outdoor use, and 80 or better for indoor use. A new international measurement more specific to LEDs is under development, but in the meantime the best way to judge how well the LED light influences the colour of objects is, if possible, to view them installed in the intended application.
Many people assume that LED lamps must be extremely energy efficient, but this is not always the case. A good number on the market are similar to or a little less efficient than the equivalent fluorescent lighting. Some poor quality LED lamps have been found to be only marginally more efficient than incandescent lighting, and less energy efficient than other types of lighting such as compact fluorescent lamps.
If lumens per watt (lm/W) are not marked on the package, divide the number of lumens by the number of Watts. The higher the number, the more efficient the product.
All lamps must be safe to operate. At a minimum this means they have met mandatory requirements and earned their safety marks. While marks such as “UL”, “CE” or other certification have no legal status in Australia, they may indicate the product meets the required safety standards. Look for at a minimum compliance claim to the standard IEC 62560.
Other label or website information
Some information on LED packaging may be misinformation. Less reputable suppliers may provide a range of logos, and other cryptic insignia, that has minimal or no value. Such may include UL, CE, RoHS, various numbers and green claims (greenwash). View such claims with scepticism.
An Australian certification scheme for LEDs
In response to many poor quality LEDs in the marketplace and exaggerated claims from some suppliers, Lighting Council Australia, a not-for-profit organisation representing Australia’s lighting industry, has developed a labelling-based certification program to assist buyers of LED products.
The Solid State Lighting Quality Scheme is a voluntary industry program that provides confidence to the market that an LED product carrying the scheme’s label matches certain critical performance claims made by the supplier (energy efficiency, light output, colour temperature and CRI). Registered products appear on a searchable database at www.lightingcouncil.com.au
Bryan Douglas is chief executive of Lighting Council Australia.