Its not good practice to put too many plugs into an extension lead – even though we all do it

Extension leads, blocks, adaptors, call them what you will are widely used; they’re a great device for increasing the number of sockets we have so we can plug in more equipment. You have plenty at home, and probably even more at work, however, you are probably using them incorrectly, potentially very dangerously!

Extension leads (or whatever you call them) were originally created when computers started coming into use more at work, to assist in powering them and their associated devices, such as printers.

IT equipment doesn’t draw much power, so these leads were created to allow more appliances to be powered from the same socket, than is possible by plugging directly into the socket.

Such leads are generally designed to handle a combined load of less than 12 amps, which at most could be up to 6 low voltage devices; they were not designed to manage the power load required by common household appliances like microwaves, hair driers and fridges.

PAT testing extension leads | pat testing Newcastle

Some of these appliances draw more than 12 amps on their own, so should be plugged directly into a socket.

Just because the extension block has 6 sockets though, doesn’t mean you can plug 6 appliances into it; the block will have a maximum load rating on the back that you must make sure you don’t go over.


  • Extension blocks should be connected directly into the socket – they should not be connected via another lead, or in a series of leads (aka daisy chained)
  • Extension blocks are not designed to be a replacement permanent power solutions
  • Extension blocks shouldn’t be used to power appliances drawing in total more than 12 amps of power

So if you’re using an extension block of any kind to power kitchen appliances; remove it immediately – you don’t need them all switched on at the same time anyway.

If you use such leads at work, in the office, that’s fine as long as it’s only IT equipment using them – unplug the additional leads, and don’t plug in your fans or heaters!



A common misunderstanding is how many appliances can be plugged into an extension lead.

For example, just because the lead has 4 sockets, it doesn’t mean you can plug in 4 appliances. You should only plug in 4 appliances if their combined power draw is no more than the capabilities of the adaptor.

Here are a 2 examples:

Computer + Monitor + printer combined are a perfectly acceptable combination to use on an extension lead, and leave plenty of space to add something else, but be careful what the something else is.

Overloading sockets increases the risk of an accident or fire

To avoid overloading sockets follow this advice from Electrical Safety First:

  • Check the current rating of the extension lead before plugging appliances into it. Most are rated at 13 A, but some are rated at only 10 A or less – the rating should be clearly marked on the back or underside of the extension lead. If not, refer to the manufacturer’s instructions
  • Never overload an extension lead by plugging in appliances that together will exceed the maximum current rating stated for the extension lead. This could cause the plug in the wall socket to overheat and possibly cause a fire.
  • Use our overload calculator (below) to check if you’re exceeding the maximum load

The Socket Calculator has been brought to you by Electrical Safety First.

For more safety information visit

  • If you must use an extension lead never plug another extension into it, to prevent over use.
  • Use an extension lead (multi-way bar type) rather than a socket adaptor (square shaped) as this puts less strain on the wall socket; some socket adaptors don’t have a fuse, which increases the overload risk.

Using extension leads increases the risk of overheating.

By |2020-01-20T20:18:49+00:00March 29th, 2017|PAT Testing Info|Comments Off on Its not good practice to put too many plugs into an extension lead – even though we all do it

About the Author:

I am Richard Ayre; editor for this site, owner of the site and the business, and a PAT testing engineer with over 10 years experience. I consider myself an expert in testing IT equipment in office environments; I have worked in many different industries for hundreds of different clients testing all kinds of electrical equipment. I am also Operations Director for the Portable Appliance Testing Trade Association As well as being the business owner I am also an employer; based in Wallsend near Newcastle upon Tyne. I am also involved in the running of the Portable Appliance Testing Trade Association as Operations Director and joint founder. "PATTA" attends important meetings and provides representation for the smaller businesses that do PAT testing in the UK, when decisions are being made that affect them.