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by W.A. Steer  PhD
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Stop! DON'T ban the bulb

Yes, I'm concerned about the environment, global warming, and about the profligate and spiralling energy consumption of the developed- and developing world. I'm also irritated by many of the headline-grabbing campaigns which, though well-meaning, appear to be more about gaining environmental 'brownie points' than actually making any real difference. Space-heating and transport use far more energy than lighting, so why the demonisation of the humble incandescent lightbulb?


Matt Prescott is heading a campaign to "Ban the Bulb" - to get the [British] government to ban the traditional incandescent lightbulb in the name of energy-efficiency and saving the environment. It's perfectly true that the ordinary lightbulb is quite inefficient at converting electricity to light (most of the energy goes directly to heat), but compact fluorescent lamps (CFLs) are not universally superior or even equivalent replacements. By all means encourage people to try them, but considering the wider picture an outright ban on the use or sale of traditional bulbs using the force of law would be a draconian measure and totally disproportionate. I'm keen on energy saving (it should invariably save you money too), but these kind of campaigns are simplistic, discourage critical thinking and ignore the elephant in the room (heating and transport).

Savings from the use of CFLs are small or comparable to other household activities...

So why pick out the lightbulb? According to Ofgem (the energy regulator), the average UK household consumes 3300 kWh electricity and 20500 kWh of gas annually. [edit: Those are 1999 figures. More recent government estimates (2005) are closer to 4600kWh for electricity. A 1-2% cut in total direct domestic CO2 emission is rather small compared to a 40% increase in electricity usage over 6 years!]

British cars are usually reckoned to have a typical annual mileage of 10000 miles.

3300 kWh electricity1800 kg CO2assorted uses
20500 kWh gas3900 kg CO2primarily used for heating, some cooking
10000 car miles2900 kg CO2
Total:8600 kg CO2
Typical annual energy and CO2 emissions for a UK household
0.54kgCO2 per kWh electricity, 0.19kgCO2 per kWh natural gas, 2.3kgCO2 per litre of petrol (gasoline) http://www.defra.gov.uk/environment/business/envrp/gas/envrpgas-annexes.pdf

Replacing three 60W conventional bulbs with 15W compact fluorescent equivalents burning for 5 hours per day saves 246kWh of electricity per year, around 140kg of CO2 (a mere 1.6% of 8600kg total).

CFLs are not perfect replacements for traditional incandescent bulbs...


Whatever their colour-designation (eg "warm white") fluorescent bulbs emit a very different spectrum of light compared to conventional bulbs. This causes what is known as poor "colour rendering", and gives the light a very starchy clinical feel. Colours are distorted and the colour saturation usually decreased, making the light seem "grey". Many artefacts in a room, especially wood and skin, can aquire an unpleasant greenish tinge. Dark fabrics, particularly blacks and navy blues, often look "faded" and/or "dusty". Food can look extremely un-appetising. These colour effects bother some people more than others, but I take great objection to the threat of a law forcing me to use economy lighting in my living-room or bedroom. I'd much rather make my CO2 savings elsewhere (eg cycling/walking rather than using a car).

The poor colour-rendering is very bad for everyone that notices it, but will be disasterous for photographers and artists.

Most CFLs cannot be dimmed

There's no CFL equivalent to the miniature halogen spotlights producing a narrow beam of light, popular in kitchens or above tables.

Because the source is "extended", CFLs cannot reproduce the "sparkle" of the light from a clear-glass (as opposed to "pearl" or frosted) conventional bulb.


CFLs rarely work well in cold locations such as garages, sheds and attics, taking a long time to warm up and having a reduced light output.

Owing to their extra complexity they are more likely to have reliability issues when subject to repeated temperature changes in such locations too.

For little-used lights in cupboards, the energy saving is utterly negligible.

Fluorescent lamps always emit a certain amount of radiofrequency interference (RFI) which may cause hums, buzzes, or whines in radio receivers and audio equipment. If this is a problem then conventional bulbs need to be used in the vicinity of the affected equipment.

A "ban" on conventional lightbulbs is disproportionate, and any law to enforce it would be disproportionate too.

There are all sorts of miniature and specialist conventional bulbs, for ornamental lights, for ovens and sewing machines. Torch bulbs. Old, even antique, slide and cine-projectors. Where are you going to draw the line?

How do you propose to enforce the law? What will be the penalty for violating it? And will it be proportionate, considering that, for example, cars are responsible for vastly more CO2 than domestic lightbulbs?

Given that the "wasted" energy from lightbulbs is merely heat, yet dedicated electric heating appliances are widely used, and many new homes are being built with solely electric heating throughout, a law banning lightbulbs would be daft.

How dare the government propose meddling with the lights in peoples own homes, while in the meantime building new roads and airport runways!

In Britain we already pay tax (VAT) on fuels; since electricity is around 3~4× the price of gas, comparing gas with electricity the tax is already roughly in proportion to the CO2 emissions.

Lighting basics

Incandescent bulbs

Conventional lightbulbs make light by passing an electric current through a very thin coiled tungsten wire; the current heats the wire to a temperature around 2700 Celcius, where it glows white hot. Incandescent literally means to become luminous due to heat, hence the term 'incandescent lamp'.

The only 'problem' with incandescent lamps is their poor efficiency; a very high proportion (perhaps 95%*) of the power put into them is turned into heat, rather than useful light. Standard (40W/60W/100W) mains lightbulbs have efficiencies around 15lm/W, while quartz-halogen bulbs may be around 24lm/W.

Fluorescent lamps

Fluorescent lamps, including 'compact fluorescents' (CFLs), use ultraviolet light from an electrical discharge (a sort of spark) within a tube to cause a fluorescent phosphor powder coating on the inside of the tube to glow. Different phosphors can be used to make different colours, but for general lighting applications a phosphor (or phosphor mix) with a whiteish glow is chosen.

The best modern narrow-diameter (T5) fluorescent tubes claim an electricity-to-light conversion efficiency of around 100lm/W, while compact fluorescents are typically only half as efficient (40-60lm/W). A CFL lamp of the same nominal light output as an incandescent typically consumes one quarter the electrical power and therefore runs much cooler.

Lamp efficiency

* Owing to the huge variation in eye-sensitivity across the visible spectrum, efficiencies of light sources cannot accurately be defined by simple percentage. Efficiency of a light-source ought to be quoted as lumens per watt (lm/W). The definition of the lumen encompasses the spectral response (sensitivity) of the standard eye. The eye is most sensitive to green light and the greatest efficiency lamp theoretically possible would be a monochromatic green 555nm and have an efficiency of 683lm/W. Such a light would reveal no colours, any object or scene would appear merely as shades (brightnesses) of green. To show colours requires a lightsource which emits light at a range of wavelengths through the visible spectrum, wavelengths to which the eye is less sensitive. So the maximum theoretical efficiency of a useful "white" lamp may be somewhere around 200lm/W. When I get time, as an exercise I'd like to calculate that figure. Bear in mind that there is no exact figure, since better "quality" light (that is light with a full spectrum of wavelengths extending close the edges of the visible spectrum) will inherently be much less efficient than an economy lightsource with just three or four dominant wavelengths.

The real energy issue: heating and transport

But lighting is just a side-issue. A distraction. Over 80% of a British household's energy goes straight into heating. This is where real savings (and real environmental savings) can be made. By turning down the thermostat, by not heating rooms which are not in use, and by turning the heating off (or right down) when the premises is unoccupied.

Contrary to popular perception, it actually takes less, and often much less, energy to heat up a house which has been left to go cold [e.g. during the day, or overnight] than it would have done to keep it warm all along.

The rate of heat loss (energy loss) from a premises due to conduction through the walls and windows etc is proportional to the difference between the inside and outside temperature. Far better to be tucked up under a thick duvet at 5am than have the central heating working hard to keep the whole house at 21 Celcius while the outdoor temperature is at its coldest!

Further reading

Created: February 2006
Last modified: 14 March 2007

Source: http://www.techmind.org/energy/dontbanthebulb.html

©2006 William Andrew Steer