Compact fluorescent lightbulbs

Performance and price have greatly improved since our last test of CFLs.
 
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03.Compare CFLs

We haven’t yet reached the lowest claimed lifespan of 6000 hours, but our results so far give a good indication of how the bulbs are performing.

Scores The overall score is comprised of decrease in luminosity (60%) and initial luminosity (40%). 
Decrease in luminosity score is based on the light output after 2000 hours operation. The closer to the initial luminosity, the better. The lowest-scoring models dimmed to the equivalent of a 60W bulb, or less.
Initial luminosity score is based on the light output of the bulb after 100 hours burn-in. The closer to the luminosity of its claimed equivalent incandescent (typically 75W), the better. The best-scoring models started brighter than their claimed equivalent.
Warm-up time is the time taken to reach 80% of maximum brightness.
Claimed wattage is the labelled actual wattage for each bulb. Our measurements indicate this is a reliable figure.
Claimed life expectancy is the number of hours the bulb should last in normal operation (about five hours on per day). The bulb’s lifetime can be reduced by unusual operation, such as very frequent switching on and off or being situated in extremely cold or hot locations.
Price per bulb is based on what we paid in November 2009. Some come in packs of two.
 

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Compact fluorescent light bulbs table

How we test

Our test is based on the Australian Standard for self-ballasted lamps. The bulbs are a mix of screw and bayonet fittings; all are “warm white”, about 15W, with a claimed equivalent brightness to an incandescent 75W bulb (except the Megaman, which claims equivalence to a 70W, and the Philips Tornado which claims 60W).

Our tester, James Thomson, installs 10 samples of each model in a rig of 150 light fittings, and burns them in for 100 hours. The lights then are put into a continuous switching cycle of 165 minutes on, then 15 minutes off.
Light output James measures the light output of the bulbs after the 100 hour burn-in, then again after 1000 and 2000 operating hours. He then calculates the wattage of an equivalently bright incandescent bulb. All but one of the bulbs on test has dimmed over the 2000 hours, but the best have dimmed by only 10% or less.
Switch-on time is the time taken to start giving out light. In our last test of CFLs, we found some took up to three seconds to activate. However, in this test all the bulbs activated almost instantly, so James hasn’t measured the actual times.
Warm-up time shows the time taken to reach 80% of maximum brightness. Most take about 30 seconds or less, which is a noticeable improvement for CFLs but still much slower than an incandescent bulb, which reaches maximum brightness almost instantly.
Failure rate James checks regularly to see if any bulbs have failed (either dying completely or dimming so much that in normal usage you’d replace it). So far very few have failed, but they’ve only been operating for 2000 hours. The minimum claimed life expectancy for these bulbs is 6000 hours, with some claiming 8000 or even 15,000 hours.

We’ll report again after 6000 hours.

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