By Florent Alzieu

LED lights have been on the general consumer market for about 2 years. In the jungle of listed products, it can be handy to know how to sort through the available models according to some simple selection criteria.

Is it better to have fewer LEDs in a bulb?

Philips and Econergyworld think that it is better to go for a bulb made up of 5 LEDs than 50 LEDs at the same brightness level. Philips says that high power LEDs (over 2 watts per LED) have longer lifetimes. They manage to retain 70% of their output at the end of their lifetime, whereas lower power LEDs drop to 20% of output.
 
Xanlite nuances this point of view. As long as an LED, high or low power, is used under standard conditions, it will have the same lifetime and give the same output at the end of its lifetime. You do however reduce lifetime and output at the end of this lifetime if you push an LED to function beyond its initial spec, to give, for example, more brightness.

Choosing the hardware and cooling system

Inside an LED light, a cooling circuit based on materials such as aluminium (which heats slowly and cools rapidly) is required. It must be placed as close to the source of heat as possible to channel it out, to be dissipated via the fins of a heat sink (see photo). The fins can also be made of plastic and be hidden inside (visible from above). Philips and Econergyworld bulbs have such systems.

For its low energy 48 LED bulb however, Xanlite has chosen not to include fins. The reason given for this by Xanlite: the bulb doesn't heat enough to need them.

Choose a product with an optical grill

Look at the cover on the surface of the lamp. On the photo you can see that the surface isn't smooth. Above each LED the surface is deformed to disperse the light homogenously. This means the light won't be concentrated over too small an area. Manufacturers offer products with various beam angles in their ranges. Make sure you check out the specs properly.

In the case of LEDs such as the one in the photo at the top of the article, the LED cover gives the beam angle. If it's in the form of a dome, the angle will be open. If it's cylindrical, the angle will decrease and the light will be more concentrated.

Immediate maximum light

An LED light reaches maximum luminosity in 0.5 seconds (time required to heat internal components). This delay is virtually unnoticeable by the user and we therefore estimate it as immediate. In comparison, compact fluorescent light bulbs with an instantaneous lighting system get to 60% straight away. Philips even claims to reach 80% with its products.

Lumens per watt

This is the key point to look at when choosing a product. LEDs are very efficient in transforming electrical energy (watts) into light (lumens). Choosing an LED light with a very good lumens per watt ratio should be a key factor in your considerations.

Low electromagnetic emissions

Recent analysis has shown that although compact fluorescent lightbulbs emit electromagnetic waves they do so to a much less alarming extent than was believed in the past. Over 300 models tested in a study commissioned by the Agency for Environment and Energy Conservation in France, only a few models got close to the European standard maximum of 87 V/m. The great majority were well below that. LED lights, like all electronic equipment, also emit electromagnetic waves but to a much lesser extent.

Low temperatures


Photo taken with a low power LED bulb

A standard filament bulb reaches internal temperatures of 2400°C (!). A compact fluorescent light bulb equipped with a cooling system reaches 45 - 60 °C and 85°C without. High power LED bulbs get up to 35 to 50 °C. Low power LEDs get a little less hot, remaining at around 25°C to 35°C.

Recycling

An LED light is 98%* recyclable. The main advantage of LEDs over compact fluorescent bulbs is that they contain no mercury (present to the order of 0.005%), nor fluorescent powder. Fluorescent powder, a layer of which is spread around the inside of the glass of the bulb, transforms light into white light visible to the human eye. This 98% figure is disputed by Recyclum, a registered eco-organisation for the collection and recycling of used lights. In 2009, Recyclum announced a record figure for the recycling of non-LED lights of 96%. This is reflected in the eco-rating for LEDs which is slightly lower than for fluo-compact lights.
Note that 32% of fluo-compact lights sold are taken to recycling facilities. They must not be broken if they are to be recycled.

* this percentage is based on the materials employed and recycling possiblities in other domains than LED lights. It is a theoretical figure.

Returns percentage

In terms of their enterprise business area (superior volumes than for individual consumers), Econergyworld gives a returns figure of 2%. There is no figure as yet for individual consumers.

Philips
was unable to give us any figures for its general consumer sector either. Over 2009, Philips sold 200,000 bulbs out of a total of 1.5 million units on the general consumer market.

Xanlite
has a returns rate of under 1% on its 48 LED series and this figure is lower for the new generation of products. There's no figure for the totality of its range at the moment.

CRI and FSCI Values

CRI stands for colour rendering index, and measures the capacity of a light source to reproduce the colours of an object faithfully in comparison to the natural light of the sun.  The FSCI, or full spectrum colour index, is a measure of how evenly a light source covers the visible areas of the spectrum.  We give you both values in each test thanks to help from the Lighting Research Center.

To finish off with, a few received ideas

Received idea n°1 : using a dimmer reduces the lifespan of an LED light This isn't the case if the light is designed to be used with a dimmer and is set up with the appropriate equipment.

Received idea n°2: turning an LED on and off can cause problems Not the case: This has virtually no impact on the lifespan of your LED.

Received idea n°3: Fluo-compact lights are the only "energy saving" lights. Not true: "Energy saving" is currently associated with fluo-compact lights but the phrase doesn't only apply to this category of product. LED lights are also low energy, as are high efficiency halogens.

Received idea n°4: LEDs are expensive. This depends on the purchase price and the amount of energy saved. The return on investment is the key question here. It generally takes between 2 and 8 years to make up your return on investment in an LED over a filament bulb. For comparison, the return on investment on a fluo-compact light is between 8 months and 4 years over a filament bulb. The comparison between LEDs and fluo-compacts isn't yet in favour of LEDs because of the high initial investment in LEDs. There's therefore no point in replacing your fluo-compact with an LED if it still works. Wait for it to go and then do it.
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