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Important Safety Information – extension leads

By Jay Woodhouse, on 8 October 2014

UCL has a general aim to not use extension leads if possible, as they can be a significant fire risk if used incorrectly. It is understood that it is sometimes necessary to use extension leads as wall mounted power sockets are not always in suitable positions and having additional sockets fitted can be difficult and take sometime. However, wall mounted power sockets are the favoured method of providing power and should be requested where long-term use of extension leads is occurring.

Electrical extension leads are not a direct replacement for a wall socket. Extension leads have a 13 amp or less rating and wall sockets a 30 amp rating. This means it is much easier to overload an extension lead, which is likely to lead to a fire.

In the use of extension leads, what is plugged in is more important than how many items. Multiple low amp items may be fine, but one high amp item, such as an electric heater, is likely to overload the lead and cause a fire.

The total ampage of the items plugged into the extension lead must be less than the rating of the lead, usually 13 amp (See table at the bottom of this blog). Check your extension cables for their rating, usually listed on the back.

Have a look at the Electrical Safety First webpage and try their Socket Overload Calculator:



  • Use wall sockets if possible
  • Use extension leads with an earth – three cable leads
  • Visually check leads for cuts, broken plastic cover or exposed wires – discard if any found
  • Ensure leads do not create a trip hazard

Do Not:

  • Use double insulated leads  – these will have a symbol with a square within a square and do not have an earth
  • Daisy chain leads, linking more than on lead together is very dangerous
  • Use reel extension leads – these are banned on all UCL sites as they are dangerous if improperly used. please dispose of any reel extension leads you may have

This is a simplified explanation and if you are unsure, plug it into the wall. I am happy to give more detailed advice about individual issues.




Table of common electrical equipment

Domestic Portable Appliance          Amps Used Watts Used
Laptop <0.5 65 – 100
Mobile phone charger <0.5 <12
Kettle 13 3000
Satellite TV box <0.5 30
Printer <0.5 50
Radio <0.5 40
Radiator 8.5 2000
DVD player <0.5 28
Hair dryer 10.0 2200
Landline cordless telephone charger <0.5 10
Computer monitor <0.5 100
Desktop computer 3.0 700
Television 42″ HD 0.5 120
Games console 0.86 <200
Washing machine 10 2200
Toaster 9.0 2000
Tumble dryer 11.0 2500
Dishwasher 10.0 2200
Iron 12.5 2800
Microwave 4.5w 1000
Vacuum cleaner 9.0 2000
Radiator (oil filled) 13.0 3000

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