LEDs - 21st century lighting

Report: Bill Whitley, Consumer NZ, June 2011

Early uses of LEDs were in small panel-indicator lights for electronic equipment and in number displays on clock radios and the like. The first LEDs were red - but as new colours were developed they were used for traffic lights and many other applications. They’ve now moved into general lighting because of their extra-long life and low running costs.

What’s good about them

Energy efficiency

LEDs are about as efficient as good compact fluorescents (CFLs) in converting electricity into light. That means an LED’s running costs are about one-fifth of an incandescent bulb that gives equivalent light. And, because this energy efficiency means LEDs produce much less “waste” heat than incandescent bulbs, light fittings run cooler.

But despite their lower levels of waste heat, LEDs must be kept cool if they’re to have a long life. That’s why many LED replacement bulbs come with cooling fins built in.

Tip: It’s not advisable to fit LEDs into closed non-vented fittings – they won’t keep cool.

Long life

LEDs have a life expectancy of 25,000 to 50,000 hours: that’s over 20 years of normal domestic use. By comparison, a traditional incandescent bulb lasts for about 1000 hours and a CFL for 6000 to 8000 hours. An LED’s long life makes it a practical option for areas where it’s difficult to replace bulbs – such as over stairways or in houses with particularly high ceilings.

They’re also physically robust. Where incandescent bulbs contain a fragile filament and CFLs have easily broken glass tubes, LEDs are made from semiconductor material often encapsulated in clear plastic.

Dimmable

Many LED bulbs can be used with compatible dimmers. This gives them an advantage over CFLs, most of which can’t be dimmed.

Instant on

LEDs provide full light instantly – they don’t have a warm-up time like CFLs.

The LED difference

The LED difference is in the way they produce light.

• Incandescent bulbs (normal and halogen) use a white hot filament - about 95 percent of the energy is lost as heat
• Fluorescent bulbs use glowing gas inside a phosphor-coated tube - about 80 percent of the energy is lost as heat
• LEDs use a semi-conductor chip that glows when an electric current is passed through it - about 80 percent of the energy is lost as heat

Often several LED are combined to make up a bulb or fitting.

LEDs are manufactured in red, green, yellow, orange, blue and white – plus infra-red (as in TV remote controls) and ultra-violet, both of which produce light outside the visible-light spectrum.

White LEDs work differently from the other types. The LED itself produces either blue or ultra-violet light, which then makes a phosphor coating glow with white light (which is similar to what happens in a fluorescent tube or a CFL).

By changing the make-up of the phosphor, the manufacturer can alter the “tone” of the light – it can range from warm white through cool white to a quite harsh bluish-white. Warm white is what most people want in their living areas.

Cost-effective?

LEDs are cost-effective because of their low running costs and long life. A 7W LED bulb costs $35 and uses $40 worth of power in its 25,000 hour life – a total cost of $75. The running costs for the equivalent 40W incandescent bulbs are much higher: you’ll need 25 incandescent bulbs at a dollar each, which in turn will consume $230 of power over 25,000 hours – a total of $255.

Energy Star

An Energy Star specification for LED light bulbs is likely to be introduced by the Energy Efficiency Conservation Authority (EECA) later this year. This will make it simple to spot top-performing LEDs. To qualify for the Energy Star mark, an LED bulb will have to meet high standards for energy efficiency, light output, colour characteristics and life expectancy.

The quality of LEDs can vary. So until Energy Star labelling for LEDs comes in, it may pay to buy well-known brands where high standards can be expected. LED light bulbs that qualify for Energy Star will be covered by a three-year manufacturer’s warranty.

What sort of LEDs?

You can buy LEDS for most lighting applications. They’re available as replacement bulbs or complete fittings that incorporate the LED(s):

• traditional light bulbs (you just plug the LED bulb in)
• LED MR16 and GU10 halogen replacement bulbs for downlights
• LED downlight complete fittings for installing in a ceiling. These have no ventilation holes, so they can eliminate the warm air leakage from living space to roof space that occurs with conventional downlights
• LED MR16 and GU10 halogen replacement spotlights
• LED spotlight complete fittings
• LED footlights. Wall-mounted for hall and stairways
• PAR38 security lights and self-contained rectangular exterior floodlights
• ropes and strips (these are flexible strips with LEDs at intervals along the strip – they’re used mainly for concealed lighting, such as under kitchen cabinets)

Consumer's findings

• LED lighting for homes are here now
• The range of LED bulbs in supermarkets and hardware chains will gradually increase as the major lighting brands get into the market
• Many LED bulbs are dimmable, but check the packaging to make sure
• LED bulbs and fittings are expensive to buy but cheap to run – and their prices are likely to come down slowly
• The long life of LED lamps makes them useful for lights that are located in inaccessible places
• When Energy Star comes in, use it to identify top-quality bulbs