LED bulbs are increasingly common and generally are a better choice than compact fluorescent lamps (CFLs). But can you trust the claims of LED bulbs to last for 15,000 hours or more without fading? We put them to the test in our lab to find out which ones last the distance and which ones fade away.
CHOICE maintains a highly professional NATA-accredited laboratory and the vast majority of our product tests, including light bulb tests, are done in-house. We have several years' experience in testing light bulbs and a sophisticated array of calibrated equipment for the task.
With so many to choose from, what makes us choose one light bulb to test over another? As with most of our product testing, our aim is to test the most popular models on the market and what you are most likely to see in the retailers.
We survey manufacturers to find out about their range of models, we look at what's in stores and we also check for any member requests to test specific models. From this information we put together a final list that goes to our buyers. They then head out to the retailers and purchase each product, just as a normal consumer would. We do this so we can be sure the products on test are the same as any consumer would find them and not 'tweaked' in any way.
How we test
Our test is based on the Australian Standard for self-ballasted general lighting service lamps (to give light bulbs their correct technical name), AS/NZS 4847.
We test at least six samples of each light bulb in a rig of 150 light fittings. The light bulbs are first burned in for 100 hours, then we measure their light output in an integrating sphere. This tells us the light bulb's initial light output in lumens.
We then put them back into the rig and run them in a continuous switching cycle of 165 minutes on, 15 minutes off, so they're on for a total of 22 hours per day. Light bulbs are usually assumed to be on for about five hours per day in typical home usage, so our test method lets us accelerate their ageing.
After a set period – usually around 3000 hours of 'on' time – we repeat the light output measurements to see whether they are still meeting their claims. We also monitor the light bulbs throughout the test period to check whether any burn out, or dim so much that they'd need replacing.
We assign the light bulbs a performance score based on how close they are to meeting their claimed light output (in lumens). The closer to their claim, the better their score. Some models exceed their claims and we score these best; while it might be annoying to find a light bulb is a lot brighter than expected, we haven't found any that are so much brighter than their claim that we think a consumer would be unhappy. It's more common that we find models that under-perform.
Models are penalised for every sample that fails. LED light bulbs should have long lifespans – they usually claim at least 15,000 hours, which is over eight years, assuming five hours 'on' time per day – and shouldn't fade much during that time.
We also measure each light bulb's energy efficiency, rated in lumens per watt; the amount of light put out per watt of electricity used. As LED light bulbs generally perform well for meeting their light output claims, we are considering incorporating energy efficiency into our scoring in future to help further distinguish the better performers.
Short cycle testing
We sometimes put light bulbs through a short cycle test. This involves switching them on and off rapidly so that they are on for 270 seconds and off for 30 seconds, for several hundred hours. We mainly did this back when we were testing CFLs, as they are particularly susceptible to failure under very frequent switching. Our tests have shown that LEDs are much less susceptible so we generally don't do this test for LEDs.
The LED lighting market is evolving, and often after 3000 hours of testing – or about one year of elapsed time – the light bulbs in the rig are no longer available in stores and it's time to test new models. But we keep a few of each model from past tests in the rig so we can see how LED light bulbs perform over several years. The longest-running model, the original Philips Master LEDbulb 12W first tested in 2011, has been going for nearly 30,000 hours (the equivalent of about 16 years at five hours per day) and is still working, though it's noticeably dimmer than when it was new.
The overall score is made up of:
- Initial luminosity score (20%)
- Subsequent luminosity score – usually measured after 3000 hours (60%)
- Failure score (20%)
A model with no failures (burn-outs) gets 100 for its failure score; that's reduced by 20 for each sample that fails during the course of the test.
Our light bulb tests use a variety of equipment. Our testers built the rig of 150 light fittings that is elevated on a wooden frame in our temperature-controlled rig room. Light output measurement is done using a calibrated integrating sphere. During light measurement, a thermocouple is connected to the light bulb to measure its temperature (a key part of how an LED light bulb is tested as per the Australian standard). The temperature and light output data are logged automatically by a computer and the data is then analysed.
Ready to buy?
Check out our latest LED light bulb reviews and see our buying guide for information on the different types and features to look for.