I have crossposted this in it's entireity to uk.d-i-y where there a number of knowledgable people and there has already been a lot of discussion.
>
>> Since I wrote that yesterday, something nagged in my mind. Since I have a
>> low voltage 20 watt halogen and a CFL (which turned out to be 18 watt) in
>> locations where I could easily measure the light output, I did just that.
>> Maybe I shouldn't have been surprised, but (correcting for the difference >> in
>> rated power) the 20 watt halogen was a little brighter, than the CFL (but
>> not by anything that you would be likely to notice). The 20 watt halogen
>> spare in my cupboard is marked as 'energy efficiency E', and the dimmer >> CFL
>> is marked as 'energy efficiency B'.
>>
>> Something is very very wrong here.
>
>What are you using to measure the light output? If your meter has a
>sharp spectral sensitivity or is sensitive well down into the red (and
>possibly IR) then you are going to get skewed results.
>
>It would be fairly trivial to rig it so that either bulb came out 100x
>better than the other - I'm not saying you've done this, just that
>it's not easy to compare the brightness of two sources with very
>different spectral characteristics.
>
>IMO, the lower the power of the CFL, the better it does compared to
>the "equivalent" incandescent. My partner has some 5W CFLs and they
>are dazzlingly bright (they're still also very new), certainly much
>brighter than the 40W incandescents they replaced.
I haven't seen any 5 watts, I've had some 7 watts from IKEA which were very poor, in the "Twinkler" category, a fraction of the light output of a 40 watt candle.
>-----------------------
>
>Since doing the crude test the day before yesterday, I decided to try and
>make it a bit more scientific and actually give the results.
>
>First, I discovered that the bulb that I got the E energy efficiency from
>was in fact a mains voltage halogen Doh!
>
>While out shopping I had a look at the low voltage halogens to get the
>current claimed energy efficiency. Here I got my first surprise. While
>every other light bulb type (including CFLs) had the energy efficiency
>rating and the lumen output on the packaging, both were curiously missing
>from every low voltage halogen that I looked at (in 2 shops selling Philips
>and Osram). The packaging had an area of white space where the energy
>efficiency diagram would have gone. Hmm.
>
>Lumens is an odd unit to use, because without any further information it
>doesn't convey a lot of information. Lumens is not simply emitted light >intensity. >
>I set up to test 3 types of lamp. A 20 watt Philips Compact Fluorescent
>Lamp (CFL); a 20 watt 12 volt halogen capsule lamp (LVH) and (because the 20
>watt CFL claimed to replace a 100 watt GLS lamp) a 100 watt GLS lamp. The
>photo detector was a cadmium sulphide device which, on checking the spectral
>response, fairly closely matches that of the eye, so differences in spectrum
>of the different lamps should be mostly eliminated. This type of detector
>has a completely liner response so comaring differences in brightness is
>easy. Each lamp was operated at the centre of a lamp shade that had white
>sloping walls that should direct most of the light in one direction. >
>First up was the 100 watt GLS lamp. We will call the light intensity 100%
>as a reference.
>
>Next was the 20 watt LVH. The intensity was 43%.
>
>Finally the 20 watt CFL. The intensity started at 24% and rose to final
>steady intensity of 39% after 8 minutes.
>
>That doesn't sound like much of an equivalence. A search around the
>internet turned up much discussion about how much of the supposed energy
>saving of CFL lamps came from using CFL lamps of lower intensity than the
>lamp it supposedly replaced. Thus giving a 5 times energy saving. The
>claimed lumen output of a 20 watt CFL is 1200 Lumens. It took quite a bit
>of searching and I failed to find a specified lumen output for a 100 watt
>GLS. What I did find is that the 20 watt lamp should really replace a 60
>watt GLS. I also turned up what I assume is the environmentalist response,
>"Most people are unlikely to notice the reduction in brightness". All I can
>say is that if that is true, then most people have a serious sight defect.
>You can't help but notice the difference, and it is fiddling the numbers.
>So I repeated what I had done with a 60 watt reference.
>
>60 watt GLS: 100% (reference)
>
>20 watt LVH: 75%
>
>20 watt CFL: 45% warming up to 69% after 8 minutes.
>
>So the 20 watt CFL isn't even an equivalent of a 60 watt bulb. I didn't
>have a 40 watt bulb in my spare cupboard, but on the numbers the 20 watt CFL
>would be equivalent to a 41.5 watt bulb. Not a *5 times* energy saving but
>only a *2 times*. We have been comprehensively had.
It's a fiddle.
If pressed I think the lamp manufacturers will admit to making the comparison using "Mood lighting" coloured GLS lamps. Seriously taking the mickey considering how bad the quality of light from CFL's is. I noticed for the first time this week in ASDA that some of these (Osram ?) are now quite heavily tinted almost like the lamps we used to see on fairground roundabouts.
If the light from these these looks a different colour it can only be because some wavelengths have been absorbed, and ergo the light output is less.
>But look at that 20 watt LVH again. It is brighter than the equivalent
>wattage CFL. That is *it is more efficient* - nearly 9% more efficient.
>Further, the CFL gets dimmer as it ages, the LVH does not.
IME by 48% in one year.
>It is clear that the CFL is the wrong solution to the environmental problem,
>and the advantages claimed are considerably exagerated. Clearly the low
>voltage halogen lamps should be marked 'energy efficiency A', and the CFLs
>should really be marked 'energy efficiency B'. Also, LVH lamps don't have
>any of the disadvantages of the CFL. And they certainly don't contain >mercury. >
>But why don't the lamp manufacturers put the energy efficiency on the LVH
>lamps? One reason is probably that they simple and ridiculously easy to
>make. They don't have anything like the scale of profit of the vastly more
>complicated CFL
European factories are already equipped to make them. Harder therefore for the Chinese tat merchants to corner the market.
>But the environmentalists have already made up their minds
>that everyone has to switch to CFL lamps regardless of the facts. >
Believe you me, *money* is behind all this.
DG