Blewbury Energy Initiative - Lighting Choices

This page discusses the options for lighting a home, focusing on lower energy use: incandescent bulbs, halogen lamps, and lower-energy choices – fluorescent tubes, compact fluorescent (often called low-energy) bulbs, light-emitting diodes, and high-intensity discharge lamps.

A table summarises some main features, there is a list of suggested bulb wattages for low-energy bulbs, and an actual case study shows how much energy and money can be saved by using low-energy lighting. There is a summary of the timetable for banning inefficient bulbs. Finally, some information on suppliers, since shops only tend to stock the most common types and sizes.

Lighting represents a surprisingly large part of the electricity consumption of a typical house. We begin with a quick summary of the domestic lighting situation, emphasising the advantages and disadvantages of different types of low-energy lighting. More detailed information is given in the sections that follow.

Light bulb, fluorescent tube and LED packages now must indicate their light output, in units called lumens. This makes it much easier to compare bulbs or tubes of different models, wattages and sizes. The differences can be considerable, so this is useful if you are worried about getting bright enough lighting. However, be careful to compare like with like – the comparison is not valid when comparing, say, a bulb or tube that spreads its light in all directions with a directional spotlight.

The most common form of domestic lighting at present is still incandescent bulbs, where light is generated by a very hot metal filament. It is a flexible source of lighting which is cheap to install but very inefficient and expensive to run. It is best used in places where light is only used occasionally and for short periods. Due to their inefficiency, incandescent bulbs are gradually being taken off the market, starting with the larger 75, 100 and 150 watt sizes, continuing with 60 watts in 2010 and all filament bulbs over 7 watts by 2012.

The popular halogen lamps are also filament bulbs, filled with a gas including a halogen such as iodine. Compared to ordinary incandescents, they run at higher temperatures and so produce a whiter light. The are also somewhat more efficient, but cost more. They provide intense white light from a very compact package, but the efficiency benefits are minor, and they still waste most of the energy as heat. More efficient halogen bulbs have recently appeared, but the energy saving is still only about 30%.

The light from fluorescents comes from a mercury plasma that produces ultraviolet light, which is converted to visible light by a fluorescent phosphor coating on the inside of the tube. Their efficiency is typically at least four times better than incandescent lights, and fluorescent tubes last much longer than incandescent or halogen bulbs. For many years they have been used in kitchens, utility rooms and garages. More efficient fluorescent tubes are now available, and even bigger savings are possible when these are combined with electronic ballasts.

There is now a variety of shapes in addition to the traditional long straight tubes, including smaller ceiling lights with reflectors for higher efficiency and compact wall fittings.

Fluorescent lights need extra components, typically a starter to trigger them and a ballast to control the plasma. There are two general types of ballast – magnetic and electronic. Electronic ballast increases efficiency and avoids flicker and hum, as well as starting up instantly and not needing a starter. The EU plans to phase out magnetic ballasts because of their disadvantages. Some types of fluorescent fittings can be dimmed.

Now widely available, CFLs (usually called low-energy bulbs) use small fluorescent tubes. Unlike other fluorescents, they are designed to work in light fittings also used for conventional bulbs. The ballast and starter are built into the bulb. They are typically at least four times more efficient than incandescent bulbs and last much longer, so are much cheaper over their lifetime. The drawbacks, gradually being overcome, are that they are dim for a short time after switching on, and most models do not work with dimmer switches. Suggested wattage ratings are often too low, so a realistic wattage list is given below. A real example of the possible cost and energy savings with CFLs is also given.

* Low-energy bulbs (CFLs) are currently the best option from the energy and cost point of view for most domestic lighting which will be on for reasonable periods, unless there are good reasons why the slow switch-on time or lack of dimming are important.

LEDs are semiconductor devices that generate light when a low-voltage current is passed through them. Although each tiny diode is not very bright, LED arrays are getting less expensive. They are excellent for battery-powered devices. Widely used as indicator lights and for text displays, brighter versions are now used in torches, traffic lights, and bicycle and car lights. They are potentially even more efficient than CFLs, come on instantly, can be dimmed, produce very little heat, and have extremely long lifetimes. LEDs are beginning to appear in domestic applications, especially for replacing directional lighting such as halogen spotlights. However, more widespread use awaits reductions in price and ways of diffusing the very directional light, though some replacements for conventional bulbs with much wider diffusion have begun to appear. The nature of LEDs could also open interesting creative possibilities due to not needing bulbs or tubes.

Discharge lamps generate light by means of an electrical discharge giving off visible light. They are widely used in applications where a lot of light is needed over a very large area, such a street lights, because they are very efficient. However, they are very slow to start up, expensive, and do not provide good colour balance, so are not much used in normal domestic environments.

Cost has been omitted as the prices of both CFLs and LEDs are coming down rapidly, and there are many special offers.

Feature	Incandescent	Halogen	Fluorescent	CFL	LED	Discharge
Typical lifetime (hrs)	1000	2000	10–15,000	8–15,000	50,000	5–20,000
Efficiency (lumens/watt)	7–17	25	60–100	45–60	20–85	70–150
Start-up time (seconds)	0.1	0.1	1 (older longer)	1	0.01	15–30
Fully bright (seconds)	1	1	A few	Up to 120	0.01	30
Dimming possible?	Yes	A little	Some models	Special models	Yes	No
Flicker	Minor	Minor	Older types	No	No	Yes
Hum	No	No	Older types	No	No	Some types
End of life	Land fill	Land fill	Recycle	Recycle	Recycyle	Recycle

Incandescent lighting is still the most widely used form of lighting for homes. The light comes from a fine filament, normally of tungsten, which is heated electrically until it gives off visible light. The filament is usually in the centre of a glass bulb, evacuated to minimise heat loss through convection.

The filament evaporates at a rate strongly dependent on temperature, but higher temperatures give more visible light for the input energy. Thus there is a compromise between the life of the bulb and its efficiency. The normal compromise gives a life of about 1000 hours, though big power fluctuations can cause premature failure. Long-life bulbs last longer but give less light for the same electricity consumption. The light is a warm white, with more red than blue in the spectrum. Some lamps are filled with an inert gas such as argon. This allows a higher temperature for the same lamp life.

Incandescent lamps are inexpensive to buy. However, they radiate most energy in the infrared (i.e. as heat) and are inefficient for generating visible light, so they are expensive to run. Lower power lamps and torch bulbs are particularly inefficient.

Because they are so inefficient they have gradually been removed from the market: the larger 150 watt bulbs in 2008, 75 and 100 watts in 2009, and 60 watts in 2010.

The lamps start generating close to their full output in a fraction of a second after they are switched on. They can be dimmed easily by reducing the temperature of the filament, either by reducing the voltage across the lamp or by pulsing the current supplied. An incandescent lamp on mains electricity has a slight flicker at 100 Hz, but this is not noticeable as the filament does not cool much in this time.

Two fittings for mains-driven incandescent lamps predominate in the UK, as shown in the pictures. Bayonet Cap (BC), fitting code B22d, is the most common. Edison Screw (ES), code E27, is less common in the UK but more widely used elsewhere; many imported lamps and light fittings use it. Other fittings include the Small Edison Screw (SES), code E14, Small Bayonet Cap (SBC), and striplights of either 221mm or 284 mm length.

The main kinds of lamp are regular, candle, reflectors (spotlights) in various sizes, globes, and striplights. A regular bulb costs as little as 25p but other lamps can cost up to about £2.

Incandescent lamps consist of glass and metal. They do not contain any materials that will harm the environment, so they can be thrown away with household waste. They should not be placed in containers for recycled glass, however, because the glass used for these lamps is not the same as the glass used for bottles.

* Although easy to use and cheap to buy, ordinary incandescent bulbs are the most inefficient and expensive source of domestic lighting. Their sale is gradually being phased out.

Halogen lamps are incandescent lamps in which the evaporation of the filament is reduced, giving a brighter light and a longer life. The bulb is filled with an inert gas containing a trace of a halogen such as iodine. The tungsten on the filament evaporates slowly and is deposited on the inner surface of the bulb. Provided the surface is hot enough, the iodine reacts with the tungsten to make a gas, which is then broken down by the heat of the filament to redeposit the tungsten on the filament. The design lifetime is normally about 2000 hours. Halogen bulbs are usually made of quartz rather than glass, as this withstands the higher heat better. This very hot surface can be a safety concern. Ideally the bulb should not be touched directly, as grease from a finger on the quartz bulb can generate a hot spot which reduces the life of the lamp.

Halogen lamps generate intense white light from quite small bulbs. They are used in outdoor floodlights and car headlights, as well as compact reading lamps and various low-voltage portable equipment. Some small bulbs include reflectors, and are very popular used as multiple spotlights giving bright, directed light in restaurants, kitchens, etc. Halogen reflector

Halogen lamps provide up to twice as much visible light as a normal incandescent bulb of the same wattage, and as the filament is hotter the light spectrum is bluer and closer to daylight. Their greater efficiency and longer life makes their overall operating cost potentially cheaper than normal incandescent lights. However, the tendency is to use halogen lights with higher power than the incandescent lamps they might replace, which nullifies any energy saving. They are dearer than normal incandescents, with bulbs costing from about £3 upwards. Some more efficient, so-called low-energy halogen bulbs have started to appear, but as the energy saving is only about 30% this is welcome but certainly not major progress.

Halogen lights can be dimmed, but since the method of maintaining the filament depends on having a hot bulb they are not ideal for dimming.

There is a huge variety of bulb types. Some operate at mains voltage, but even for normal domestic use many light fittings include transformers so that the bulbs operate at low voltage. This makes wiring easier and safer, but if the transformers are not switched off there is some continuously wasted energy. Common types are small capsules or bulbs, and lights with reflectors (e.g. GU10; see pictures), as well as the small, thin tubes used in outdoor floodlights.

Halogen lamps contain very small quantities of halogens and halogen-hydrogen compounds, but the amounts are insignificant (only a few millionths of a gram). The lamps can therefore be thrown away with household waste. As they are made from quartz they cannot be recycled with glass.

* Although more efficient than ordinary incandescent bulbs, halogen lamps are also unacceptably wasteful of energy and expensive to run compared to other light sources.

A fluorescent tube generates light by creating a plasma in mercury vapour contained in a glass tube. The plasma generates ultraviolet radiation. The inside surface of the tube is coated with a fluorescent phosphor which absorbs the ultraviolet and generates visible light. The colours generated depend on the phosphors used. Typically the light is concentrated on a few colours, for example yellow and blue, and the human eye interprets this as white. Fluorescents for general use typically produce one of several colour blends:

Because of the peaky spectrum of light generated, colours viewed under fluorescent light often differ from their colours in daylight – in particular reds can look darker. Tubes with three phosphors (triphosphor) have better colour rendition as well as typically being brighter.

In domestic use, many houses use fluorescent tubes in kitchens, utility rooms, garages and bathrooms. They are used much less often in living rooms, bedrooms, etc. as fluorescent light and fittings often seem colder and more 'industrial' – using warm white tubes can help with this.

Ultraviolet lamps omit the phosphor and transmit the ultraviolet radiation directly. They are used for disinfection chambers and sun beds. Black-light fluorescents convert the original ultraviolet light into the near ultraviolet, which can then generate strange theatrical effects when shined on paints and other materials which fluoresce in visible colours.

This section discusses the traditional fluorescent tubes that have been available for many years as well as some improved modern varieties, while low-energy bulbs (properly called compact fluorescents) are treated separately in the next section. The important distinction is that compact low-energy bulbs work in the same fittings as incandescents, while other fluorescents need dedicated fittings.

The main advantages of fluorescent lights over ordinary or halogen incandescent lamps are that they generate much more visible light for the same input energy, last much longer, and their surface is much cooler.

A rough rule is that they use only about a quarter as much energy as incandescents to produce the same amount of light. However, the light output often depends on the colour balance – the cooler mixes tend to be more efficient than the redder ones, so for example a white tube will usually produce more light than a warm white one of the same wattage. However, there are slightly more expensive warm white variants (e.g. GE Polylux XLR) that do produce more light while also claiming improved lifetime. It is also worth noting that it can take a fluorescent a few moments to come up to full intensity, especially in a cold environment, and that the light output drops by about 20% over the life of the tube. The typical lifetime is usually stated to be about 10,000 hours, with some tubes claiming 15,000 or even 30,000 hours, but this depends on how often the tube is switched on and off – sometimes a life of 50,000 on/off cycles is claimed.

The oldest types of fluorescent tubes are being phased out under EU legislation, replaced by compatible tubes with more efficient phosphors. These can reduce power consumption by about 10%. It is also possible to replace a conventional starter with an inexpensive electronic plug-in canister (e.g. Philips Power Saver Set). Combined with more efficient tubes, the consumption is then reduced by about 30%.

Fluorescents require extra equipment in addition to the tube. In older-style fittings a starter heats electrodes at each end and then opens the circuit. This triggers a spike of voltage to start the plasma, which often flickers on and off a few times before becoming continuous. A magnetic ballast (consisting of an inductor) assists in generating the initial spike, and then limits the current in the tube, which otherwise would become excessive after the plasma has been created. Such fittings sometimes flicker and hum in an irritating way at 100 Hz, especially as they age. The light can cause moving machinery to appear stationary. The EU is planning to phase out this older type of fitting.

Modern fittings are available that have electronic ballasts with no separate starter, and operating at higher frequency (e.g. 25,000 Hz). The light comes on instantly without flickering, and annoying hum and flicker are less of a problem. Electronic ballasts can be designed to support dimming of fluorescents, keeping the filament hot while reducing the current across the tube. However for this to work there must be a good match between the dimming control and the tube. Some lights with integral ballast have been developed to provide dimming in conjunction with incandescent dimmers.

The flickering of some old-style fluorescent fittings disturbed some people, causing migraines and sometimes triggering epileptic fits. This should be better with the modern fittings, but evidence of whether this is still a problem is sparse.

Conventional fluorescent tubes come in a variety of lengths and diameters. The main diameters are:

There are also circular and U-shaped tubes in various sizes. In general, the longer the tube the higher the wattage and light output.

A standard fluorescent tube costs from about £3. For example, a 58-watt tube (often used in kitchens or utility rooms) might cost £5, with a warm white version offering more light output and longer lifetime for £6. More unusual designs can cost up to perhaps £15. Wherever possible use newer high-efficiency triphosphor types for more light and better colour rendition while using the same or less energy. The range of tubes and fittings in DIY or electrical shops tends to be quite limited, but a list of online suppliers is given below.

In recent years a number of more compact and efficient designs using different tube configurations have appeared. Sometimes confusingly called compact fluorescents, these differ from the low-energy bulbs (CFLs) described below because, like traditional fluorescents, they do not include a ballast in the tubes and so cannot be used in incandescent-type fittings. Some of these have four pins and others only two; the ones with two pins have built-in starters. Examples are shown in the two pictures at right. Often used in low-energy light fittings, they are required by some UK building regulations to prevent use of incandescent replacements

There are ceiling lights that use several parallel, shorter tubes in recessed reflector fittings that are designed to maximise light output to the room. These are mainly designed for public buildings and offices (typically with false ceilings) rather than domestic use.

However, some newer wall-mounted designs are quite acceptable for domestic living areas. These use fairly short tubes, sometimes bent to form an extended closed shape, as in the picture, and placed behind a glass or plastic diffuser. These fittings produce a lot of light and lie fairly flat on the wall; they are on sale in DIY and electrical shops.

Fluorescent tubes contain some mercury (less than they used to) and so require special treatment, available at local waste disposal centres. Do not put them in with your normal rubbish. If you break a fluorescent tube, ventilate the room well before cleaning it up to avoid inhaling mercury vapour.

* Fluorescent tubes are a very effective way to reduce both energy usage and costs.
The main choice is between dedicated fluorescent fittings with a separate ballast, and more conventional fittings and lamps that require the use of compact fluorescent bulbs, discussed in the next section.

Compact fluorescent lamps are low-energy light bulbs that can be used as direct replacements for conventional bulbs. A CFL has an integral electronic ballast and starter, and typically either a bayonet or Edison screw fitting so it can be used in the same fittings as incandescent bulbs. This section concentrates on CFLs, often simply called low-energy bulbs – more conventional fluorescent tubes requiring fittings with separate ballasts are discussed in the previous section.

When CFLs were introduced they were too big and heavy for many existing light fittings, and cost £10 or more. They took quite some time to reach full brightness, and were usually dimmer than expected. Current models are far better, offering both the original straight-tube shapes and very compact spirals that fit into many existing light fittings. They are also much lighter in weight. Other shapes are also available, such as globes and candle lamps. CFLs that can be dimmed are now available but not yet common or inexpensive. CFLs are still a bit dim at turn-on, but brighten up fairly quickly. Costs have come down to the point where the most popular sizes can sometimes be found in multiple packs for less than £1 each. There are also offers, sponsored by utility companies, for multi-packs of common sizes costing only a few pence per bulb. The situation is continuing to change rapidly, with improved versions appearing at a rapid pace.

However, CFLs are still noticeably dimmer in cold surroundings, and are not suitable for locations where they are only switched on for very short periods (e.g. a cupboard).

CFLs share the advantages of fluorescent tubes. The much more compact packages do somewhat reduce the amount of light produced for a given amount of energy, but compared to incandescents the energy usage, running cost and lifetime are vastly improved – see the real-life example below. The energy saving is so large that they pay for themselves within a few months. And although one CFL might cost more to buy than one conventional bulb, the far longer lifetime means that the cost of buying one CFL should really be compared to buying about ten incandescent bulbs. However, beware of buying cheap, possibly unbranded, bulbs with efficiency ratings of B rather than A and lifetimes of less then 10,000 hours.

Many people have noticed that the wattage equivalents claimed on CFL packaging tend to be overstated. These usually suggest replacing an incandescent bulb by a CFL with a wattage rating of one-fifth or less. Unfortunately the worst example is the most common one, replacing a 60 watt incandescent by an 11 watt CFL. This is often too dim, discourages people from using CFLs, and leads to the very common statements that CFLs cannot provide adequate lighting. It is usually better to go up to the next available rating, using a CFL with about one-quarter of the wattage rather than one-fifth – for example replacing a 60 watt incandescent bulb with a 14 or 15 watt CFL, or a 100 watt incandescent with about a 23–25 watt CFL. There is a suggested list of replacement wattages below.

CFLs come in a wide and expanding variety of sizes and shapes, as shown in the pictures. However, if you want to put one into a constricted light fitting it often takes care to find a CFL of the right wattage that fits in. The main styles currently available are: small U-tubes (two to four tubes), spiral, globe (like a conventional bulb), candle, and reflector. Many CFLs are Edison screw, and although some light fittings and lamps in the shops are also Edison screw, it is quite difficult to buy Edison screw replacement bulb sockets for fitting yourself.

The most common ratings range from 7–8 watts up to about 23–25 watts. Larger sizes and a full range of shapes are harder to find in shops. For example, to replace a 150 watt conventional bulb a 30 watt CFL is recommended. A list of mainly online suppliers, offering a far wider range of bulbs and fittings, is given below.

Another advantage of CFLs is that they produce much less heat than the equivalent incandescent bulb, so that a higher-wattage CFL can be used in a fitting that can only handle a relatively low-wattage incandescent. However, for CFLs of more than about 20 watts it is still necessary to be sure there is adequate ventilation.

CFLs that can be used with conventional dimmer switches are still not common but they are becoming available – they cost more and reports on their performance are mixed. There are also CFLs with light sensors built into their bases, so that they can automatically turn on at night.

There have been some reports in the press about low-energy bulbs causing migraines and epileptic fits. Hard evidence on the number of occurrences and the exact types of bulb has not been given. Older fluorescent bulbs could flicker and disturb some people, but modern fluorescent fittings and low-energy bulbs work differently so it is not clear how widespread the problem, if any, really is.

Prices of low-energy bulbs are wildly variable, so it is well worth shopping around. Multiple packs of the most common sizes can cost well under £1 per bulb. Single bulbs – often exactly the same ones – vary hugely in price. Unusual sizes and types are often less expensive, and indeed may only be obtainable, from specialist companies on the internet. Electricity suppliers and others sponsor some nearly free special offers. But beware of very cheap or free unbranded bulbs. Some of these work reasonably well, but others are dim or take a long time to reach full brightness.

Compact fluorescent lamps contain a very small amount of mercury (much less than they used to) and so require special treatment, available at local waste disposal centres. Do not put them in with your normal rubbish. If you break a bulb, ventilate the room well before cleaning it up to avoid inhaling mercury vapour.

Most people who replace their bulbs with CFLs do so a few bulbs at a time, making it difficult to evaluate the energy and cost savings accurately. However, a member of the Energy Initiative replaced virtually all of the incandescent bulbs in his house over a very short time, and carefully monitored the change in electricity bills. This was quite a clear case: the house already had fluorescent tubes in the kitchen, utility room and bathroom, with ordinary incandescents everywhere else. The incandescent bulbs ranged from 60 watts to 150 watts, and the two dozen or so replacement CFLs from 11 watts to 30 watts. Some 60 watt bulbs were replaced by 15 watt CFLs rather than the 11 watt ones recommended on CFL packages, and 100 watt bulbs were replaced by 23 or 24 watt CFLs, in order to get adequate light.

Comparing electricity bills over a full year with bills from previous years, the energy consumed was reduced by nearly 1500 kilowatt-hours over the year. At current electricity prices that saves at least £180 per year. The cost of the CFLs was paid back within a couple of months. However (as noted above), if we compare the price of one CFL with the ten or so ordinary bulbs that would be needed over its much longer lifetime the CFL is probably cheaper to buy, even without taking the hugely reduced electricity consumption into account.

* At the present time, compact fluorescent bulbs are a very effective way to reduce both energy usage and costs. For most domestic purposes, they are probably the best choice at present.
The main choice is between dedicated fluorescent fittings with a separate ballast (discussed in the previous section), and more conventional fittings and lamps using compact fluorescent bulbs.

When choosing low-energy bulbs, and also fluorescents, the equivalent wattage ratings given to replace existing incandescent bulbs is almost always too optimistic. The formula usually used is one-fifth or less of the incandescent wattage, and this is why many people say that low-energy lighting is too dim. These suggested ratings tend to be worst for smaller wattages, and for special packaging such as candle bulbs. In the table below we give more realistic values, which tend to be about one-quarter of the equivalent incandescent bulb wattage.

Incandescent bulb wattage	Low-energy bulb wattage
25	7
40	9 – 11
60	14 – 15
75	18 – 20
100	23 –25
150	30

Passing current through special types of semiconductor diodes generates light. The colour generated depends on the materials making up the diode. For many years red, yellow and green LEDs have been used as indicator lights, or for simple alphabetic or numeric displays. LEDs can be shaped, for example to produce the widely used 7-segment numeric displays in digital clocks. The invention of blue and then ultraviolet LEDs led to the production of white LEDs. White-ish light is generated either by combining diodes using different materials, or by coating a diode generating ultraviolet with a suitable phosphor. The operating voltage across the diode is about 1 volt, which means that battery operation is an attractive option. Another attractive feature is that they last far longer than ordinary lighting, with lifetimes claimed to be 50,000 hours or more. This makes them useful for reducing failures and maintenance, especially in safety-critical applications or in places that are difficult to access. For example, arrays of LEDs are now used for traffic lights, some car lights, etc.

LEDs come on at full intensity, and are very easy to dim. They would therefore overcome some of the limitations of current low-energy bulbs.

The light emitted by one diode is not very bright (though that is improving), but several diodes can be combined to make a light that is more compact and uses much less electrical energy than an incandescent bulb. Arrays of many diodes are fabricated using some of the same large-scale production techniques used for electronics. The light is emitted directionally, unlike domestic light bulbs, but that is a useful feature for many of the current applications, such as torches or replacements for halogen spotlights.

The efficiency of the brightest LEDs has been increasing steadily. Even at fairly low efficiencies (comparable to incandescents) they have the advantages of low-voltage operation and long life, and so have been in widespread use as indicator and illumination signs for quite some time. More recently, they have become widely used for portable devices such as torches and bicycle lights because even small, low-power batteries produce sufficient light and last a very long time.

LED lighting is under very active development. Efficiency is now comparable to fluorescents and low-energy light bulbs, which means they generate very little heat. For the future it is generally expected that LEDs will become much more efficient, but in order to achieve this a problem called ‘LED droop’ has to be overcome – this is a reduction in light output efficiency as the electrical current carried by the LED increases. Higher efficiency and improved production methods would reduce the present relatively high prices of LED lights.

Three other problems are now being overcome. The blue-ish colour balance of many ‘white’ LEDs needs to be improved, but warm white lights are now becoming available. More serious is the directionality – at present the main domestic use of LED lights is to replace halogen spotlights, but good omni-directional bulbs are now beginning to appear. Finally, the price of LEDs is still very high, and although the savings due to their high efficiency and very long lives are considerable, the up-front cost of replacing all the halogen spotlights in many houses is still considerable. However, prices are dropping steadily.

The future of LED lighting has great potential. Producers predict that efficiencies two or three times better than fluorescent lights seem possible. When this is combined with ways to produce diffused light to fill a room, there is a possibility of a true revolution in lighting since arrays of LEDs need not come in the form of bulky bulbs or tubes. Rooms might be lit by large-area flat panels or interesting shapes.

Light-emitting diode lights would generally be classified with other electronic goods, and should be brought to local waste recycling centres.

* Light-emitting diodes are potentially even more efficient than CFLs, but more development is needed before they can be regarded as a complete solution for general domestic lighting. At present their best application is to replace halogen spotlights and other directional lighting.

The technology of these lamps is somewhat similar to that of fluorescents. A discharge is created in a tube, but in discharge lighting the light is produced directly in the visible range rather than ultraviolet. As a result even higher efficiencies, up to 150 lumens per watt, can be achieved. To reach the rated light output it is normally necessary to evaporate a metal in the tube, so that the lights can take about 15–30 seconds to reach full brightness, and may need to be off for 30 seconds before they will re-light. Discharge lighting is therefore normally used in environments where bright lighting over a wide area is required for long periods, for example in sports halls, warehouses, street lighting, agriculture, and indoor gardening. They have also been used, with some controversy over their brightness and colour, for vehicle headlights.

The discharge is triggered between tungsten filaments along a quartz or alumina tube. The most common technologies at present are metal halide (picture) and high-pressure sodium, both of which give a white-ish light. Low-pressure sodium, widely used in street lights, is the most efficient of the lamps, but produces an almost purely yellow light which makes recognising colours impossible. The earliest lamps used mercury vapour, which gave a blue-ish light including considerable ultraviolet, which had to be filtered out.

A high-intensity discharge lamp typically costs around £30 and lasts between 5000 and 20,000 hours.

Most discharge lamps contain some hazardous materials and so require special treatment, available at local waste disposal centres.

* Although very efficient, discharge lamps have too many drawbacks for general use in domestic lighting.

A combination of voluntary measures and EU legislation has already made a huge difference to what is allowed for sale, and this will continue. Starting in September 2009, all non-clear (i.e. pearl or opal) non-directional incandescent bulbs have not been allowed to be manufactured or imported into the EU. This includes standard, candle, and globe bulbs. In addition, clear incandescent bulbs over 75 watts are now banned, with lower wattage clear bulbs gradually being eliminated: 65 watts in September 2010, 45 watts in September 2011, and anything over 7 watts in September 2012.

Reflective bulbs (e.g. spotlights and downlighters) and specialist bulbs (e.g. for ovens, fridge and traffic lights) are not yet included but will soon be phased out, mostly by September 2012.

Older types of fluorescent tubes are also being phased out, with more efficient replacements already available.

These are some of the main companies producing low-energy lamps, with links to their websites:

Common styles and sizes of low-energy bulbs (CFLs), fluorescent tubes and LED lights can be obtained from supermarkets, electrical, and DIY stores. There are often special deals (subsidised by energy supply companies), especially on packs of several CFL bulbs. However, the choice tends to be quite limited, e.g. if you want CFLs of more than 20 watts.

A wide range of lamps can be bought or ordered from:
Didcot Electrical Wholesalers, 66–68 Broadway, Didcot OX11 8AE (01235-819181) and from
DC Lighting, Unit 11, Harrier Park, Hawksworth, Southmead Industrial Estate, Didcot OX11 7PL (01235-511003).

Internet sources can be less expensive, particularly if buying in any quantity, and offer a very full range if you look around. Some useful suppliers (in alphabetical order) are: