Think your new energy-efficient compact fluorescent lamp doesn't throw as much light as the old incandescent bulb it replaced? You're right, a new independent study has found.
Most new CFLs fail to live up to manufacturers' claims that they emit as much light as an equivalent 75-watt incandescent lamp, tests by a team of UNSW optics researchers and engineers have shown.
Most performed poorly regardless of retail price, ranging from $3 to $16, and only one in four meets the minimum standard required in other countries - but not in Australia or New Zealand - to justify a claim of equivalence to an incandescent wattage for light emission.
The problem is not so much in the CFLs themselves but in the labelling that rates their equivalence, says Professor Stephen Dain, one of the authors of a report published in the journal Clinical and Experimental Optometry. Co-authors were Ms Gloria Yuen, also of the UNSW School of Optometry and Vision Science, and Associate Professor Alistair Sproul, of the UNSW School of Photovoltaic and Renewable Energy Engineering.
"We found that in two-thirds of cases a CFL that is claimed to be the equivalent of a 75-watt incandescent lamp delivers a lot less light than you expected. Some are only the equivalent of an old 60-watt lamp," says Professor Dain.
"The public seems to be disappointed when they replace an incandescent lamp with a CFL claimed to be equivalent. This study shows that they are entirely justified in their disappointment. They're really not as good as they're made out to be, although they are still a whole lot better in energy efficiency."
Under a recent Federal Government policy, incandescent lamps can no longer be sold in Australia and CFLs have proved most popular as substitutes on price and energy efficiency. The team tested 33 CFLs of different brands and designs labelled as being 75-watt equivalent and tested them for various attributes, including power consumption, light output, colour rendering, colour temperature and light distribution.
They found that while CFL design and performance has improved in recent years and most performed satisfactorily, only nine out of the 33 met the equivalence claim.
Globe and spiral-shaped CFLs distributed light more evenly - much like incandescent lamps - making them the best choice for unshaded light fittings. Double, triple and quadruple biaxial CFL lamps tended to throw light sideways, with very little being directed downwards.
They note that all CFLs sold in Australia are imported and conform to different standards according to the country of origin.