What type of cable you need depends on the application – what you are going to use the cable for. Here’s some information to help you choose the right cable.
The capacity of a cable to ‘carry’ electricity depends on the cross-sectional area of the conductors – the copper cores which conduct electricity. Cross-sectional area is measured in mm². Cable which is thicker – has a larger diameter core – can ‘carry’ more electricity. Where the core of the cable is round, the cross-sectional area can, of course, be calculated from the diameter or radius using π (area = π x r²).
Although the cross-sectional area of a cable’s conductors determine the capacity to conduct electricity, cable is commonly ‘rated’ by reference to current or power rather than conductor size. Understanding these ratings involves three linked concepts:
- current – the flow of electrons in the cable and measured in Amps
- voltage – the electrical pressure applied to the cable and measured in Volts
- power – the product of current and voltage (Amps x Volts)
In the UK, the ‘declared’ voltage of the domestic electricity supply used to be 240 Volts and is now 230 Volts (the original regulation is here and the amendment which changed the law is here). There is a permitted variation not exceeding ten per cent above or six per cent below the declared voltage. In practice, most homes continue to receive a supply which varies around 240 Volts.
Cables which have conductors with a cross-sectional area of 0.75mm² are rated at 6 Amps or 1,380 Watts (6 Amps x 230 Volts is 1,380 Watts). The table shows the common cable sizes and ratings in Amps and Watts.
Current rating (Amps)
Power rating (Watts)
Using a cable which is too thin or does not have a high enough rating increases the risk of fire (caused by the cable getting hot) and electric shock (caused by the insulation failing due to the heat). Here is a table which shows the typical requirements of light bulbs and appliances.
Likely rating – Amps
Likely rating – Watts
Filament Light Bulbs
0.1, 0.17, 0.26, 0.43
25, 40, 60, 100
Fluorescent Light Bulbs
0.03 to 0.08
7 to 18
LED Light Bulbs
0.01 to 0.06
3 to 13
Fridges and freezers
1.3 to 1.7
300 to 400
Dishwashers and Washing Machines
Any cable must be capable of carrying the maximum load which might be applied. Some thought needs to be given as to what the maximum load might be, for example:
- 0.5 mm² cable would be enough to power a light fitting with 10 x 4 Watt LED light bulbs, but it would not be enough if the same fitting was fitted with 10 x 100 Watt filament bulbs
- 0.75 mm² cable would be enough to to use an extension lead for a microwave, but it would not be enough to use as an extension lead for a washing machine
Although thinner 0.5mm² cable is sometimes used for lighting, we do not sell it. The reason is that BS EN 60598 – the applicable British and European standard for lights – requires cable to be at least 0.75mm² for light fittings. All the lights we make – wall and ceiling lights and Custom Lighting pendant lights are wired with 0.75mm² cable to comply with the British standard. And we won’t sell cable which is likely to mean our customers won’t comply with the standard.