Traditional incandescent bulbs, which are being phased out of British shops, lose just a fraction of their brightness by the time they stop working, but energy-saving ones lose 22 per cent of brightness.
The figures come from an in-depth report from E&T, the leading trade magazine published by the Institution of Engineering and Technology.
It concludes that consumers are being routinely misled about the efficacy of low energy light bulbs, or compact fluorescent bulbs as they are technically known. "There is a big difference between what most bulbs' packaging promises and what the reality is. It's no wonder so many consumers are dissatisfied with the bulbs," said Dickon Ross, the editor of E&T.
The report examined all the existing evidence, including tests undertaken by the German consumer organisation Warentest, which was submitted to the European Commission, and official US Department of Energy tests.
The German organisation tested 18 energy-saving bulbs in 2008. After 10,000 hours, three of the 18 bulbs had stopped working completely and the average reduction in brightness for the remaining 15 CFLs was 22 per cent.
Meanwhile, the US Department of Energy tested 124 bulbs for 2,400 hours – far less than the 10,000 hours that most energy-saving bulbs are meant to last. It found that 28 per cent had stopped giving out adequate light by this stage.
Traditional incandescent bulbs, in contrast, lose no more than 7 per cent of their brightness by the time they stop working, after about 2,000 hours.
Brightness in light bulbs is measured in so-called lumens, a more accurate way of assessing the light given out by a bulb than watts, which purely measures the energy that flows into the bulb.
However, the E&T report points out that many manufacturers exaggerate the brightness of their CFLs.
The Energy Savings Trust recommends that 11-14W CFLs are the equivalent to a 60W traditional bulbs; advice that is echoed by most lighting manufacturers in the UK.
However, the European Commission itself warns consumers many claims are "not true". "The light output of 15W compact fluorescent lamp is slightly more than the light output from a 60W incandescent," it states on a website for consumers.
In August it became illegal for retailers to import 100W, frosted or pearled incandescent light bulbs, or to sell them once their current stocks have run out. Instead consumers have to rely upon CFLs or low-energy halogen bulbs.
From September 2011, 60W clear incandescent bulbs will be banned, followed by a ban on all remaining incandescent bulbs in September 2012.
Dr Paula Owen at the Energy Saving Trust, the Government-backed body, said good energy saving light bulbs would only be noticeably dimmer after six to ten years. She added: "Typically, a low energy light bulb used in a living room, for example, will last 10 times longer than a traditional one. In this time, the householder will have saved about £65 on their energy bill.”
Source:
http://www.telegraph.co.uk/earth/earthnews/6600015/Energy-saving-light-bulbs-get-dimmer-over-time.html
