Illuminating research calls long-term brightness of energy-saving lightbulbs in to question

Consumers may already consider CFL Energy saving light bulbs too dim, but an investigation by E&T magazine has found that CFL lamps will also lose significant brightness over time.

The article also reports that official guidance telling us which CFL bulb to buy is overly optimistic with regards to their performance, with the combined factors resulting in a CFL lamp ending up 40 per cent dimmer than the incandescent bulb it was bought to replace.

Furthermore, recent EU legislation promises more confusing labelling and could result in lamps that fail to meet the standards originally recommended by the UK Government’s Energy Savings Trust. The latest EU directive on the lamps has reduced the required lifespan, approved longer warm up times and allowed an increased loss in brightness – particularly over the first 2,000 hours.

Concerns have also been raised over how long the CFL bulbs last, particularly if subjected to repeated switching on and off. The Energy Saving Trust has dropped rapid cycle testing – where bulbs are repeatedly turned on and off to simulate actual use – despite research in the US showing that up to 25 per cent of samples failed during such tests.

Part of the problem with the new energy saving bulbs relates to consumer complaints about poor brightness performance, which the E&T article claims is in part due to the overly optimistic equivalence ratios adopted by the Energy Saving Trust and used by many manufacturers on bulb packaging. While the equivalence ratios used give impressively low power consumption figures, they are also a key component in consumer dissatisfaction when comparing the new bulbs with the incandescent versions they replace.

Currently the Energy Savings Trust bases its recommendation on power consumption and uses a 5:1 equivalence ratio, so a 60W incandescent bulb would be replaced by a 11-14W CFL and a 100W incandescent would be replaced by a 20-23W CFL. Other authorities base their recommendations on the actual amount of light produced which gives a different picture.

The European CFL Quality Charter recommends that the ratio should be 4:1, while the Lighting Research Centre at the Rensselaer Polytechnic suggests 3:1. While energy savings might not be as compelling under such ratios, consumers would still use a fraction of the energy of a conventional bulb and would have more satisfactory output performance.

Commenting on the article, E&T Editor-in-Chief, Dickon Ross said: ‘Our article goes some way to explaining consumers’ dissatisfaction with CFLs and it’s interesting that the major manufacturers have switched their focus to the development of LED lighting, though it too has its problems.’

Further information:

http://kn.theiet.org/magazine/issues/0920/energy-saving-bulbs-0920.cfm

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