I have just used a photographic exposure meter to compare the light output of a CFL bulb with various pearl light bulbs.
The CFL is a 20W bulb claimed to be equivalent to a 100W bulb. It has had about 1 year of evening use. Its measured light output is a little LESS than a 60W 2000h pearl bulb rated at 555 lumerns, and ~40% of a 100W 2000hr bulb. Power ratio for the same light output is thus 1/3 not 1/5. This is a
66% over claim in this case.
The small print on the CFL package says it is equivalent to a 1000h "soft colour" bulb. This is presumably much lower efficiency than normal pearl bulbs. This claim is therefore presumably accurate but misleading.
Having replaced several 100W pearl light bulbs with "100W" CFLs, we have reverted to pearl in all but one room.
These misleading claims must be understood and ruled out. CFLs are not yet ready to replace conventional bulbs. The calculated efficiency gains are greatly exaggerated.
Please copy to naive environmentalists, band-wagon jumpers, and government ministers.
I've carped about this for years. The claimed outputs are nowhere near 5 times the rated wattage. When Which? did a test on CFLs I wrote to them pointing this out and asking if they could rate bulbs by their actual output, not their claimed one.
My pleas fell on deaf ears. Hope you have better luck than me in getting someone to listen.
I would tend to agree... however if you are going to argue this, you ought to be ready for questions about how your light meter responds to the narrower spectra of CFLs Vs incandescents.
On 26 Feb 2007 03:36:31 -0800 someone who may be "gmw" wrote this:-
A camera light meter. Not quite the right thing to measure the output of light bulbs, though it will give some indication.
What sort of CFL were you measuring with the camera meter? Some designs take a while to achieve full brightness.
I note with interest the different conditions. From what you have typed it appears that you compared the output of a one year old CFL, measured with your meter, to the claimed output of two bulbs, the age of which you don't state. Fascinating.
Where were these installed?
For what reason(s)?
Though earlier you typed that these claims were presumably accurate. Why should accurate claims be ruled out?
Incorrect. In most cases there is now a suitable energy saving bulb. The number of cases where such bulbs are not suitable has been and is being reduced.
At one time such bulbs were really only suitable for relatively large fittings with lamps that were left on for long periods. This was because of the size/weight of the bulbs, the length of time they took to reach full output and a relative lack of robustness of the starting mechanism. However, that was in the early 1980s. The engineering of energy saving bulbs has progressed a long way since then.
But if you look at it another way, it's going to cost you *at least* three times as much in electricity to get the same light output from a conventional bulb as from a CFL.
Experiments done under laboratory conditions with excellent test gear can produce all sorts of reliable and replicable results but the human eyes vary enormously. I'm quite prepared to concede that it's my eyes at fault rather than the CFLs themselves but, for me anyway, I'll not give these wretched things house-room.
On Mon, 26 Feb 2007 14:20:19 +0000 (GMT) someone who may be "Dave Plowman (News)" wrote this:-
Not to mention the cost of buying all the GLS bulbs that will be needed to replace the one CFL bulb over its lifetime and install them. The latter cost may be zero in a domestic setting.
The light meter was a Gossen Sixtar hand held CdS meter, used in incident light mode. As you say, it gives some indication. To check that my results were not too wildly out, I also made an extinction photometer that I placed between pairs of bulbs, which gives similar results.
The CFL is a Philips B22 BC 15000h 1200 lumen 140mA 230-240V order code 544742xx Our mains voltage is 230V nominal, during the test I measured 228V on a basic DMM early evening. The afternoon voltage is 232V. The voltage variations obviously affect the light outputs of both types of lamp.
I took readings with the Sixtar set to 100ASA (so that EV = LV) at 5 minute intervals at the same distance of ~1.5m. At switch on from room temp the LV was ~3.0. After 5 minutes the LV was ~3.5 After 30 minutes the LV was ~3.7 A new 240V 60W 2000h pearl bulb (555 lumen) gave an EV of 3.9 and was subjectively as bright as the CFL A new 240V 100W 2000h pearl bulb (gave an EV of 4.9 and was subjectively much brighter than the CFL A new 240V 100W 1000h pearl bulb gave an EV of 5.0
The pearl bulbs were fairly new. Pearl bulb outputs are less susceptible to aging than CFLs, and pearls are statistically likely to be younger than CFLs for most of their lives, if CFLs last as long as claimed.
I think the problem could be due to supply voltages. I suspect that CFL output is more sensitive to supply voltage than pearls, in which case we need 230V rated CFLs if we are to get the claimed output.
All the bulbs were for general illumination, fitted to ceiling light fittings, mostly with open lampshades above them.
In living rooms a single "100W" CFL room light was too dim to read comfortably by etc even after fully warmed up, giving similar light to a 60W bulb. A single 100W pearl was adequate. In rooms where lights are normally off, the CFL's slow warm up and alleged reduced life caused by cycling could be a problem. CFLs would be left on much longer than pearls, negating energy saving.
The claims are no doubt accurate in the technical terms defined in the small print. Those compare the CFL light output with "soft colour" (low efficiency) type of bulb that is not used for general illumination. I suspect that they are both measured at 240V, but that CFLs may produce much less light at 230V than do pearl bulbs. Is this so? I presume that this is why the actual output of the bulbs in service is way below the "headline" equivalent output, which is why I say the claim is misleading.
I would be delighted to fit CFL bulbs that, at 230V, give similar light levels to 100W 2000h (long-life) pearl lightbulbs at the same voltage, for most of their lives, and do not suffer infant mortality or DOA.
Re lack of robustness, I recently purchased 3 CFLs (in much heavier packaging than pearl bulbs). One had broken glass, one failed quickly, the third is still going strong. Filament bulbs are much more robust. I have no financial interest except as a consumer. I want CFLs to work. They have never yet worked as advertised for me, or many others.
I agreed with you about 5 years ago, but have just retried CCFL. A single 24W globe replacing a 100W incandescent far outshines it, and 3x 11W bent tubes easily replace 3x 40W bulbs.
In both cases though they take some 5 minutes, (or more), to creep up to full brightness, so I can see a case for retaining incandescents where the lamp is on for only brief periods.
I agree and have commented on this group before. Having seen lots of cfls at very reduced prices and then discovered they were not as bright as the previously used 100W pearl I went to TLC and bought a
25W CFL, having failed to find anything at Tesco, Morrisons, Wilkinsons and B&Q. Even this bulb is barely the same as a 100W and unfortunately was not the same colour temp as the cheaper CFLs or Pearl bulbs.
At least they haven't banned Pearls like they have in Australia.
If anyone can provide a link to reasonably priced CFLS of 25 or 30W I would be grateful.
You can get 26, 32, 45, 55, 60 and 105 wat ones (mostly with ES caps) from . I've no idea how good they are and the higher power ones are quite pricey.
I've tried a number of CFLs, so far they have all been rubbish. They start off poor and become worse fairly rapidly. They may well last for years as the makers claim but the light output will fall off in a way that does not occur with incandescent lights.
I have several 9-14W CFLs. I would say that each does exactly what it says on the tin. A 9W CFL produced about 9W of output, and that's NBG.
This is a well-known problem here, and unfortunately, it makes many peoples' first experience of a CFL a poor one which they choose not to repeat. Softone lamps do indeed have a lower light output, so this is marketing bullshit at its worse, particularly as rather few people use Softone lamps.
My normal advice, often repeated here, is to use a factor of 4 between a filament lamp and a CFL, and that would be a CFL with exposed tube (an outer bulb loses some more light). Reflector CFL's do much worse, because a folded tube is a really bad light source to try and reflect in any direction without significant light loss. (The one exception here is the GE Genura R80, which at 23W produces more light than a 100W flood lamp, but it uses a significantly different technology from standard CFLs.) The other problem you can find is that the different size/shape of the CFL may mean it's light source is not in exactly the position the luminare expected, if it was designed for a filament lamp.
Look for 25W CFLs.
They are, but you fell into the marketing trap which most CFL first-timers fall into. Try to move on without dismissing the whole technology.
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