Light Bulb Technologies - Explained

In this article we explain the four main types of domestic lighting technology, to assist your purchasing decision.
With the regular incandescent light bulb being phased under EU legislation, you the consumer, now faces a much wider choice when replacing your household lamps.   That choice is often now based around the ‘technology’ within the bulb and can greatly affect light output, performance, energy use and price.   This article takes a look at the 4 main technologies for domestic lighting being; incandescent, halogen, compact fluorescent & LED.
This is the traditional technology; the one you will all most likely have in your home but it is also under attack from EU legislation (see separate article) and being phased out.  This is because it is inefficient: Light is produced by essentially heating the thin tungsten filament until it glows.  However, in order to generate light, the filament must generate a large amount of heat and around 80% of this heat it wasted.  The filament in a light bulb is actually flammable and without the glass envelope it would simply burn up.  So to combat this oxygen is removed from the glass envelope (the bulb) and replaced with non reactive or inert gases, which prevent the filament burning.  With the phasing out of this technology, consumers now need to look elsewhere for their lamps.  A typical incandescent light bulb will burn 60 watts of power, last just 1000 hours, and give a light output of around 700 lumens.  

Key Facts:  Cheap to buy but expensive to run as inefficient.  Short life span when compared to alternatives.  Generates large amounts of wasted heat. Slowly being phased out. 


A halogen lamp works in a very similar way to an incandescent bulb but with a crucial difference.  Halogen gases inside the bulb help in maintaining the life of the tungsten filament by redistributing spent tungsten back onto the filament.  This allows the lamp to run at a much higher temperature and with improved efficacy (light output).   As the lamp must be run at a higher temperature, the smaller ‘bulb' surrounding the filament is made of stronger quartz glass, allowing a higher pressure.  All of this adds up to improved lamp life over a regular incandescent lamp and because they consume less energy, makes them more cost effective to run and maintain.   Halogen lamps are now being placed within a traditional bulb envelope, so from a consumer point of view the option of a standard fully dimmable light bulb is still available – only now it will use less power, give a brighter light and last twice as long!  A typical 60w equivalent will use 42 watts of power, last 2000 hours, and give a light output of 630 lumens.

Key Facts: More expensive to buy than incandescent, but with twice the life.  Generally cheaper to run than incandescent due to more efficient burning technology.  Excellent lumen output and colour rendering.  Generates large amounts of wasted heat.

Compact Fluorescent (CFL) Energy Savers
Compact Fluorescent bulbs are essentially just small fluorescent lamps which can be used in existing light fittings, to replace the standard light bulb.  The main difference is that a CFL will normally contain its own ballast (energy regulator), where as a standard fluorescent tube will have an external ballast.  Fluorescent lights use a gas, which emits an invisible ultra violet light when ‘excited’ by electricity.  This ultra violet light hits the white coating (phosphor) on the inside of the lamp which produces the light you see.  There are a number of benefits to CFL’s as unlike the other technologies here, they do not rely on heat to generate light, making them much more energy efficient and with a much longer life.  However, their light output when compared to incandescent bulbs has been widely criticized, often over shadowing the energy and temperature benefits.  In addition the lamps cannot generally speaking be dimmed and can be slow to ‘warm up’.  Recently manufacturers have begun offering CFL’s in traditional looking envelopes, with a variety of colour temperatures, and in fast start technology.  There are retrofit options for nearly all house holds lamps, including GU10’s, striplights, reflectors, floodlight bulbs, candles, rounds, and GLS.  A typical 60w equivalent will use 11w of power, last 15000 hours and give a light output 570 lumens.

Key Facts: More expensive to buy than halogen or incandescent but lasts around 10-15 times longer.  Uses much less energy as more efficient.  Generally non dimmable and can be slow to 'warm up'

Light Emitting Diodes (LED)
Once the preserve of indicator lights on households appliances, LED is now fast becoming a source of regular light in the home.   LED works differently to incandescent and halogen as there is no actual filament within the lamp.  Instead light is created by passing a voltage across a diode.  There are several advantages to LED, principally being exceptionally long life up to 50,000 hours as there is no filament to burn out.  Their compact size and relatively cool operating temperature means that they can be used in a variety of compact fittings and housings.   In terms of light output per circuit watt, LED’s far outperform their conventional relations, with figures commonly around the 50lm/W (lumens per watt) mark, as opposed to incandescent offering only around 10lm/W.   The principal disadvantage with LED is their high upfront cost.  Where as a halogen GU10 can be purchased for around £1.00, an LED true alternative will set you back up to £25.00.  Over the lifetime of the lamp you will actually save money due to lower running costs and long life.  A typical halogen 50w equivalent will use just 8 watts of power, last 35000 hours and give a light output of 400 lumens.
Key Facts: Most expensive to buy but lasts up to 50 times longer than incandescent. Very low wattage making them very cheap to run.  Saves money over the lifetime of the bulb.  A difficult technology to dim.

But which is best?
There is no strict answer as to which technology is best, as each has a number of advantages and disadvantages.   Choosing the right lamp is likely to concern a number of factors including taste, application, use and budget.   In hard to reach areas where lights are left on for longer periods of time, CFL may offer the greatest benefits.  However, If you are more interested in the total cost of the lamp over its life time then LED might be considered.  But again, if you require full dimming compatibility with exceptional light output then halogen is still a firm favourite.  One thing is for certain though, in years to come you won’t be choosing incandescent.