Sunday, 18 March 2012

Review: LED light bulbs

Lighting accounts for 19% of global electricity usage, so improving the efficiency of light bulbs can make an important contribution to reducing carbon dioxide emissions. For the past fifteen years, compact fluorescent light bulbs (the classic ‘energy-saving light bulbs’) have been the focus, but despite their dramatically lower energy requirements they do have their own well-publicised problems. Instead, the future lies in a different technology: LED lighting.

Homes of the future will have DC circuits powering LEDs with a lifespan so long you may never need to replace them, but for now LED lighting needs to be ‘backwards compatible’ and fit into normal light bulb sockets. LED light bulb technology is still in its infancy — LED bulbs only surpassed the efficiency of compact fluorescent bulbs in the past couple of years — so we were pleasantly surprised when we saw LED bulbs on sale at Greenlife in Totnes recently. Despite the high price — £16.99 — we just had to give one a go.

The first thing you notice about an LED bulb is its strange appearance. Using DC technology in an AC circuit means that each bulb must have a built-in rectifier and heat sink, leading to the characteristic metal ‘fins’. The second thing you notice is the resultant additional weight — the three bulbs depicted above give the same light output, but whereas the incandescent bulb weights 29 grams and the compact fluorescent bulb weighs 71 grams, the LED bulb weights in at 127 grams.

Weight isn’t really a problem, but light quality is. This LED bulb uses only 5 watts, but is intended to be equivalent to a 60 watt incandescent bulb (for comparison, a compact fluorescent bulb with the same luminous output would use 11 watts). Unfortunately, the bulb is only this bright in a relatively narrow cone directly below it — even at an angle of only 45 degrees, it already feels more like a 40 watt incandescent bulb. As a result, we’ve relegated it to the light socket directly above the ironing board, where its limitations will be less noticeable.

There’s no doubt that LED light bulb technology will improve significantly over the coming years, with reductions in weight and price and improvements in efficiency and light quality, but for now LED light bulbs aren’t quite ready for use in the home.

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