LED advice: How to select a quality LED
Advice on how to select a quality LED is provided by BRYAN DOUGLAS, chief executive officer of the Lighting Council Australia.
Solid state lighting is a rapidly developing technology offering a useful alternative to traditional light sources. LEDs – a form of solid state lighting – can provide excellent illumination in a wide range of applications and are highly energy efficient. They also have a long life – lasting up to 50 times longer than incandescent lamps and two to five times longer than fluorescent lamps, making them ideal for hard-to-access locations.
LEDs are durable and can withstand vibration and shocks. They are not affected by regular on/off switching, which is good for areas such as bathrooms. In addition, they are at full brightness as soon as they are switched on and many are fully dimmable.
Tests on some LED products found in the marketplace, however, indicate a wide variation in product quality and how effectively they may light a space. Some lower quality LEDs sold may not provide sufficient light, may flicker when dimmed, change colour through life or fail prematurely.
LED products are still in a comparatively early stage of development, and few have undergone rigorous testing in real-life settings over a prolonged period of time. Accordingly, users need to be aware before investing in the technology.
COMMON LED PERFORMANCE INDICATORS
When selecting an LED, facilities managers are encouraged to look for the important LED product features summarised below, including light output, colour characteristics, lifetime and energy consumption.
Lamp equivalence claims
Be cautious of claims that lamps are equivalent to common incandescent or halogen reflector lamps. The best LEDs are currently about four to five times more efficient than their typical incandescent lamp equivalent. This means that for an LED lamp claiming to produce as much light as a 60 watt incandescent or 50 watt dichroic reflector lamp, it will need to use at least 12 watts of energy. Look for sensible numbers on any claim of equivalence and compare products.
Light output (lumens)
Another way to determine whether an LED is suitable is to look for information about the light output, measured in lumens (lm). The higher the number of lumens, the more light is emitted. Lumens are the best, most accurate way to compare two different types of lighting. If the lamp carries a lumen output rating, it may also indicate that it was actually tested for this performance – a good sign.
For an LED lamp to provide equivalent light to the common 50 watt MR-16 dichroic downlight, it must produce a minimum of 480 lumens. To achieve light output equivalent to the best quality MR-16 downlight, it will emit 900 lumens. Always look for a clear statement of light output in lumens.
Unfortunately, the 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. It is also important to note that LED light sources tested under laboratory conditions will always have a higher light output than the LED lamp when used in normal conditions. If unsure about the specifications, potential purchasers should contact the manufacturer or supplier to understand how the light output of the product has been measured. The most useful measure is when light output from the complete light fixture is measured.
Lamp lifetime (hours)
Some LEDs claim to have very long rated life, such as 60,000 hours or more, but have been tested 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 of operation and then a prediction of the light output decay is used to determine operational lifetime. Look for realistic lifetime and manufacturers who can back up their lifetime claims, either with testing or certification indicated on the product packaging.
Lamp warranty period (years)
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 lifetime is claimed, look for a corresponding longer warranty of perhaps five years. Look for a clear statement of warranty period.
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. Shades range from warm-white (similar to a regular, incandescent lamp) to cool white or bluish white (daylight). Look for and make sure to choose the colour that best suits the intended application and that you are most comfortable with.
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 (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. Look for and make sure to choose a CRI number to suit the application.
Energy efficiency (lumens per watt)
Many people assume that LED lamps must be extremely energy efficient; however, this is not always the case. Many LEDs currently 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.
The energy efficiency of a light is measured in lumens per watt (lm/W). If this measurement is not marked on the package, simply divide the number of lumens by the number of watts. The higher the number, the more efficient the product. Look for an energy efficiency rating on 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, a compliance claim to the standard IEC 62560.
Other label or website information
Some information on LED packaging may in reality be misinformation. Less reputable suppliers may provide a range of logos and other cryptic insignia that has minimal or no value. These may include UL, CE, RoHS, various numbers and green claims. Look for and view such claims with scepticism.
LED CERTIFICATION SCHEME
In response to many poor quality LEDs in the marketplace and exaggerated claims from some suppliers about their product’s performance, Lighting Council Australia has developed a labelling-based certification program to assist purchasers 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. Registered products appear on a searchable database on Lighting Council Australia’s website.