Historically, electric bulbs (lamps) have generated light by heating a tungsten filament until it glows. These are known as incandescent lamps and are a relatively inefficient means of creating light as much of the energy is converted to heat. By adding halogen gas into the sealed lamp unit around the filament, it was found that a greater amount of light was generated whilst still using the same amount of power. As a result, tungsten halogen lamps became exceptionally popular, particularly being used in recessed downlighters. However, halogen lamps are still relatively inefficient. Keeping up?

The alternative and more efficient forms of lamp are those which emit light through an electric gas discharge – this includes fluorescent lamps as well as low and high pressure discharge lamps, such as metal halide and sodium. In the case of fluorescent lamps, light is generated mostly by ultraviolet radiation from the gas discharge interacting with a phosphor coating. Still making sense?

A further development in lighting in recent years has seen the increased use of LEDs (light emitting diodes). Whilst LED technology has been around for many years, it is only recently that the light colour and output from them has been significantly enhanced. Unlike other forms of light, LEDs generate light from a solid state semi-conductor with no gases being involved. They can be very efficient and be made to produce different colours of light. 

The table opposite outlines the efficiency of each type of light discussed. The measure of a lamp’s (bulb’s) light output is not its wattage, this only relates to the amount of power being consumed by the bulb i.e. a 100w bulb consumes five times more power than a 20w bulb – it does not however mean it is five times brighter. Light output is measured in lumens and therefore the energy efficiency of a lamp can be judged by the lumens output per watt of power consumed. Basically, the lower the figure, the less efficient the bulb is.

Part L of UK Building Regulations currently states that, for a light source to qualify as energy efficient, it must have a lumen/watt output greater than 40 – this must take into account any inefficiencies in the light fitting as well as the bulb itself. 

So in short, the higher the figure, the more energy efficient the bulb is, and guess what....all light fittings on this website, with the exception of some LED products, have an output equivalent or greater than 40 lumens per watt.