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
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
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.
Totally agree that light for light CFL bulbs not only are overstated but
won't make a blindest bit of difference to the planet.
They do however last long enough to be cost effective. Replacement bulbs
add up to a lot of money..
On 26 Feb 2007 03:36:31 -0800 someone who may be "gmw"
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
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
I have tried a variety of CFLs and I now call them "3D" lamps - Dull, Dismal
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
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.
Homebase. Can't remember the price, not cheap.
It was a great disappointment at first switchon
but I came back to it about an hour later and it
was brighter (and maybe very slightly whiter)
than the 100W bulb it replaced.
The 3x 11W folded types are inside frosted glass
shades and they are less successful. I don't
know why.... perhaps colour temperature, maybe
CFL's need matching shades.
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
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
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
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
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
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.
Giles Whittaker, Kirkliston. BAe Systems (Retired)
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
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.
On 26 Feb 2007 10:56:25 -0800, email@example.com wrote:
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.
Does it look like a typical CFL with folded tube?
I've had best results with Philips Softone CFLs which look more like a
normal light bulb.
The 'stick' CFLs might be a bit directional too.
I now use a mix of CFL and a few well placed low wattage halogens.
That makes sense to me.
I was looking for possible excuses for the disparity between the
maker's claims and my measurements, but it would make the disparity
between the claimed and actual performance comparison between filament
bulbs & CFLs @ 240V even worse.
I have just logged a complaint with the Advertising Standards
I seem to have stirred up a hornets nest with my first ever posting.
I will try higher powered CFLs, if I can find them. The best I could
find the last time I looked at B&Q etc is 20W / "100W".
I agree that they would save my electricity bills. However I suspect
that they would also increase the much worse pollution in by China
more than is saved in the UK.
At least we in the UK have the benefit of nuclear power (for the
moment...) (whose pollution is containable by good engineering) and of
wind power (occasionally, when the wind blows strongly enough at the
right time, which is not as often as the hype would have us believe).
Still, who am I to spoil the party. There is a lot of money to be
made, rearranging the deckchairs on the green bandwagon. Some of it
MIGHT do more good than harm.
(ducks for cover)
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