I don’t know how you feel, but I have so much more confidence in making purchases and asking for advice when I have a bit of background knowledge. So in this post I hope to boost your confidence in purchasing your lighting needs with a basic run down on domestic lighting language.



The light fitting is known as a “luminaire” – whether for indoor or outdoor use – a wall light, a chandelier, a flush fitting, or even a table lamp or floor lamp are all luminaires. Table and floor lamps are known as “portable luminaires”.


Lamps v Light Bulbs


As a consumer a lamp is simply a table lamp (as the image), however, in the lighting industry the term “lamp” refers to the light bulb, such as a reflector, halogen, GLS, fluorescent tube, spotlight etc. In other words the light source.


In domestic lighting there are several lamp types that we will be familiar with.




Mains Voltage (V)

Most of us are aware that our domestic mains electricity supply is 240V AC*. In our mains supply, voltage enables the flow of electricity to light the lamp. Such a voltage is capable of causing skin burns, severe electric shock, and even death. This is why all electrical appliances should be fitted by a relevantly qualified electrician.

However, if we use a lower voltage supply this risk is reduced considerably (see below Safety Extra Low Voltage).

It is worth noting that it our mains voltage is described as ‘low voltage’ because in industry much higher voltages are used. Low voltage is categorised as 50V to 1000V AC.

Safety Extra Low Voltage (SELV)

Categorised at below 24V AC, SELV is generally utilised in luminaires for bathroom and outdoor use, although there are other luminaires that are SELV. SELV luminaires require an isolating transformer. Other luminaires have integral transformers which can usually be found inside the ceiling plate.

In items such as recessed downlighters the transformer is generally fitted within the ceiling void. The mains power cable is connected to the transformer which is then connected to the luminaire by a lower voltage cable. This reduces the 240V electricity supply to a much safer 12v on the luminaire side of the transformer.


A watt is the basic scientific unit of power from your electricity supply. A 40w lamp therefore consumes 40 units of electrical power. You will see the term “wattage” in various places. A lampholder (the part of the luminaire that the lamp fits into), will be marked with the maximum wattage lamp that the luminaire can safely take; the packaging of the luminaire will usually display this information and lamp packaging will show the wattage of the lamp that you are purchasing.

The wattage marked on the lampholder is the maximum wattage that the lampholder/luminaire is designed to take. You are at risk of burning out the lampholder if a higher wattage than the recommended is used.


A lumen is the basic unit for the quality of light produced by the light source, ie the amount of visible light emitted from the lamp. In future all packaging for lamps will display the lumen output of the particular lamp. The lumen output of a lamp can vary significantly – factors such as the specific manufacturer, and the technology that they use, and of course the actual quality of the lamp itself.

For example take the following BELL (British Electric Lamps Ltd) incandescent 60W clear decorative candle bulbs.

Lamp Wattage      Lumen (l) Output

60w                             655

40w                             350

25w                             170


In summary, the voltage enables the flow of electricity to light the lamp, the wattage is the amount of power that the lamp consumes and a lumen is the measurement of how much visible light is actually perceived through the human eye.

Colour Temperature

Colour temperature refers to the objective scale of the colour appearance of near white light sources, ie lamps. Colour temperature is measured in Kelvins.  It is important to note that colour temperature does not relate to the actual temperature of the lamp itself, but our perception of the colour of the light produced. See below the colour temperature of some of the most popular lamp types we use in domestic situations, together with its colour code and the description.

Colour Temp °K Colour Code Description
2700 827 Warm White
3500 835 White
4000 840 Cool White
6000 860 Daylight


This is just a sample of the colour temperatures we use in domestic lighting. You may have seen tropical fish tanks or pet reptile tanks where specific colour temperatures of lamps replicate their natural environment or habitat.


Refraction is the way light travels through a transparent material such as glass. The speed of the light travelling through glass or plastics is much slower than travelling through air, travelling at about two-thirds of the speed in air and generally causes the light beam to bend. You see this effect on luminaires such as glass and crystal chandeliers.


Double Insulated or Class II Luminaires

Certain luminaires are double insulated which ensures protection from electric shock. All live parts are surrounded by sufficient insulation materials to ensure we cannot come into contact with the electrical components once the luminaire is correctly installed in normal operation. Often Class II luminaires will be produced in certain plastics such as polycarbonate, which have good insulation properties.

Period properties with no earthing in the building’s electrical wiring will require double insulated luminaires to comply with current regulations. Your electrician should advise you of the need for double insulated products.

The following symbol will be displayed on the base of the luminaire on all double insulated or Class II luminaires and portable luminaires.


Task Lighting

Lighting used for specific tasks in our home is known as task lighting. For example, a floor lamp or table lamp used for tasks such as reading, sewing etc.

General Lighting

General luminaires such as the ceiling pendant for overall general lighting within a specific room or area.

Accent Lighting

Accent lighting is used to illuminate without causing any distraction from the functional aspects of the room, or maybe highlighting certain areas of decorative interest. It may also assist in creating a specific mood.


Further Information

There are so many terms used in the industry, the list could go on and on. If you are unsure of any terminology and would welcome any further advice please get in touch and one of our experienced members of staff would be happy to assist.


* The voltages stated are for the UK only. For further information on other countries’ power supplies please consult the relevant country’s governing body.