Low Energy Lightbulbs are not that bright

Have you replaced a 60W traditional tungsten bulb with a 60W-equivalent low energy compact fluorescent and thought it’s not as bright as it was. You’re not imagining it. I’ve been doing some tests of my own, and they’re not equivalent.

Comparing light sources is a bit of art as well as science, and lacking other equipment, I decided to use a simple photographic exposure to give me some idea of the real-world performance. I pointed the meter at a wall, floor and table top. I didn’t point it at the light itself – that’s not what users of light bulbs care about.

The results were fairly consistent: Low energy light bulbs produce the same amount of light as a standard bulb of three to four times the rating. The older the fluorescent, the dimmer it was, reaching output of a third at a thousand hours use. Given that the lamps are rated at two to eight thousand hours, it’s reasonable to take the lower output figure as typical as this is how it will spend the majority of its working life.
This gives a more realistic equivalence table as:

Quoted GLS
Realistic GLS
8W 40W 25-30W
11W 60W 35-45W
14W 75W 40-55W
18W 100W 55-70W

Table showing true equivalence of Compact Fluorescent (CFL) vs. conventional light bulbs (GLS)

So what’s going on here? Is there a conspiracy amongst light-bulb manufacturers to tell fibs about their performance? Well, yes. It turns out that the figures they use are worked out by the Institute of Lighting Engineers, in a lab. They measured the light output of a frosted lamp and compared that to a CFL. The problem is that the frosting on frosted lamps blocks out quite a bit of light, which is why people generally use clear glass bulbs. But if you’re trying to make your product look good it pays to compare your best case with the completion’s worst case. So they have.

But all good conspiracies involve the government somewhere, and in this case the manufactures can justify their methods with support from the EU. The regulations allow the manufactures to do some pretty wild things. If you want to look at the basis, it can be found starting here:

For example, after a compact fluorescent has been turned on it only has to reach an unimpressive 60% of its output after a staggering one minute! I’ve got some lamps that are good starters, others are terrible – and the EU permits them to be sold without warning or differentiation. One good thing the EU is doing, however, is insisting that CFL manufacturers state the light output in lumens in the future, and more prominently than the power consumption in Watts. This takes effect in 2010. Apparently. Hmm. Not on the packages I can see; some don’t even mention it in the small print (notably Philips).

However, fluorescent lamps do save energy, even if it’s only 65% instead of the claimed 80%. All other things being equal, they’re worth it. Unfortunately the other things are not equal, because you have the lifetime of the unit to consider.

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A standard fluorescent tube (around since the 1930’s) is pretty efficient, especially with modern electronics driving it (ballast and starter). When the tube fails the electronics are retained, as they’re built in to the fitting. The Compact Florescent Lamps (CFL) that replace conventional bulbs have the electronics built in to the base so they can be used in existing fittings where a conventional bulb is expected. This means the electronics are discarded when the tube fails. The disposable electronics are made as cheaply as possible, so it may fail before the tube.

Proponents of CFLs says that it is still worth it, because the CFLs last so much longer than standard bulbs. I’m not convinced. A conventional bulb is made of glass, steel, cooper and tungsten and should be easy enough to recycle – unlike complex electronics.

The story gets worse when you consider what goes in to the fluorescent tubes – mercury vapour, antinomy, rare-earth elements and all sorts of nasty looking stuff in the various phosphor coatings. It’s true that the amount of mercury in a single tube is relatively small, and doesn’t create much of a risk in a domestic environment even if the tube cracks, but what about a large pile of broken tubes in a recycling centre?

So, CFLs are under-specified and polluting and wasteful to manufacture, but they do save energy. It’d be better to change light fittings to use proper fluorescent tubes, however. They work better than CFLs, with less waste. I don’t see it happening though. At the moment descrete tubes actually cost more because they fit relatively few fittings. People are very protective of their fittings. The snag is that with CFLs you need at least 50% more bulb sockets to get enough light out of them.

Standard bulbs produce less light than they could because a lot of the energy is turned into heat (more so than with a CFL). However, this heat could be useful – if your light bulbs aren’t heating the room you’d need something else. This is particularly true of passageways and so on, where there may be no other heating and a little warmth is needed to keep the damp away. The CFL camp rubbishes this idea, pointing out that in summer you don’t need heat. Actually, in summer, you don’t need much artificial light either, so they’d be off anyway. Take a look at document “BNXS05 The Heat Replacement Effect” found starting here for an interesting study into the matter – it’s from the government’s own researchers.
But still, CFLs save energy.

Personally, however, I look forward to the day when they’re all replaced by LED technology. These should last ten times longer (100,000 hours), be more efficient still, and contains no mercury anyway , nor even any glass to break.  The snag is that they run on a low voltage and the world is wired up for mains-voltage light fittings. I envisage whole light fittings, possibly with built-in transformers, pre-wired with fixed LEDs which will last for 50 years – after which you’d probably change the whole fitting anyway.

Ah yes, I hear the moaners starting, but I want to keep my existing light fitting. Okay, sit it the gloom under your compact fluorescents then.


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