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Individually switched extension lead with surge protection

Updated: 23 October 2026

You want a switched bar under the television, the console or the PC, and the listing says surge protected. An individually switched extension lead with surge protection still has one 13 A plug. The joule figure is a claim about a brief spike, not a licence to add more appliances. Peter F., editor for DIY & tools, used the surge column in the [extension lead individually switched comparison](/hub/sockets-and-extension-leads/extension-lead-individually-switched) on 20 October 2026, plus Masterplug SWSRG wording. This is not a lab test. A qualifying purchase can earn a commission at no extra cost to you.

You want a switched bar under the television, the console or the PC, and the listing says surge protected. An individually switched extension lead with surge protection still has one 13 A plug.

Our top picks

Masterplug Masterplug SWSRG4210N

Best overall

Masterplug Masterplug SWSRG4210N
9.4/10about £9.50
View offer
Pro Elec Pro Elec PL15330

Best value

Pro Elec Pro Elec PL15330
8.8/10about £9.99
View offer
Addtam Addtam TH-UK04U3

Alternative

Addtam Addtam TH-UK04U3
8.2/10about £15.99
View offer
On this page
  1. 1.Joules are not amps
  2. 2.The figures in this set
  3. 3.The £1,000 sentence
  4. 4.When the listing disagrees

Joules are not amps

A joule, on a surge lead, is energy the protector is claimed to absorb. Masterplug's SWSRG family sheet prints 370 J beside a separate load line of 3,120 W at 240 V. The load line is the 13 A fuse. The joule line is the spike. A higher joule number does not let you plug in more. Addtam's 1,050 J does not make that bar a heavier supply than the Masterplug's 370 J. Both are still 13 A leads. The same sheet says the surge neon shows when to replace the lead if the protection circuit has failed. That is a status lamp, not a promise the lead will stop a lightning strike. A surge-protected lead does not increase the power from the socket, does not make overloading safe, and is not an RCD. Daily overload steps stay on how to use an individually switched extension lead.

The figures in this set

Two Masterplug leads state 370 J in the surge story and in the table. The SWSRG4210N is the four-socket 2 m bar at £9.50, with 4.8 from 1,232 reviews. The SWSRG6210N is the six-socket 2 m bar at £12.49, with 4.7 from 1,535 reviews. Both claim power and surge LEDs and the connected-equipment wording below. They are the rows where the joule figure and the product name point the same way. Bedroom brightness of those LEDs is a separate complaint, covered on the best individually switched extension lead page.
Masterplug Masterplug SWSRG4210N

Testsieger

Masterplug Masterplug SWSRG4210N
9.4/10about £9.50
View offer

The £1,000 sentence

On the two Masterplug SWSRG listings, the bullets describe connected-equipment wording of up to £1,000 if surge damage occurs within three years. The family sheet adds that this wording is UK only and that it follows registration. One review of the six-way lead says registering the surge warranty was difficult. That is a practical limit, not cash sitting on the bar. Read the conditions on the paperwork. This comparison has not tested a claim. The sentence does not cover an overload from high-heat appliances, and it is not a reason to ignore a hot or melted lead.

When the listing disagrees

The Masterplug SWC4210N is the row you should not tidy into a yes. It is £9.49, with four switches and 2 m. The attribute table says surge protection and 370 joules. The title does not say surge. The box line says a switched lead, not a surge lead. UK reviews say the surge parts and the LEDs are not fitted, and buyers have returned it because the page did not match a surge lead they already owned. Do not call it a 370 J lead. A Screwfix Masterplug, model SWC42N-XD, is listed without surge protection. That trade listing is not this ASIN. It shows how close a plain switched code sits to a surge code. Buy the SWSRG number if you wanted the joules.

Common questions

What does a joule rating mean on these leads?
It is the energy the surge protector is claimed to absorb, not the current the bar can supply. Masterplug's SWSRG sheet uses a joule that way and keeps 3,120 W at 240 V as a separate load line. The load line matches the 13 A fuse. A joule rating does not stop a lightning strike, and it does not make a kettle and a toaster safe on the same lead. If the listing prints no joules, do not invent a number for it.
Does 1,050 J let me plug in more than 370 J?
No. Addtam's 1,050 J and Masterplug's 370 J are both surge claims on a 13 A plug. The higher number is not a heavier continuous rating. You still share one fuse across every socket that is switched on. USB ports on the Addtam bar do not add to that fuse either. A review says those ports do not fast-charge, which is a charging limit, not a surge limit.
What does the Masterplug £1,000 sentence cover?
On the SWSRG4210N and SWSRG6210N bullets it is connected-equipment wording of up to £1,000 if surge damage occurs within three years. The family sheet says UK only, after registration. One six-way review found that registration difficult. It is not printed on the other brands in this set. It does not cover an overload you caused by sharing high-heat appliances, and it is not a reason to ignore a hot or melted lead.
Is the SWC4210N actually surge protected?
Do not treat it as surge protected. The attribute table says 370 joules. The title and the box line do not say surge. UK reviews say the surge parts and the LEDs are missing, and some buyers returned the lead for that reason. If you need the 370 J claim, buy the SWSRG4210N. The SWC4210N can still be a plain four-socket switched bar at £9.49, once you have dropped the surge requirement.
Why does Dewenwils print 13 A in the surge field?
The surge field says 13 amps. The bullet says 270 joules and a 13 A resettable breaker. Thirteen amps is the continuous rating of this kind of UK lead, not a joule figure. Read 270 J as the surge claim and 13 A as the fuse and breaker line. Do not add them together. A bullet that says four switches on a six-way title is a separate conflict, and reviews describe a switch on each socket.

Related pages

Individually switched extension lead buying guide

Extension lead individually switched

Best individually switched extension lead for 2026

How to use an individually switched extension lead

Extension lead indicator lights too bright at night

Sources

Sources taken from the research digest. Listings were scored on 22 October 2026. This page did not run a lab test.

  1. Plugs and Sockets etc. (Safety) Regulations 1994 (retrieved 22.10.2026)
  2. Electrical Equipment (Safety) Regulations 2016, regulation 35 (retrieved 22.10.2026)
  3. Electrical Safety First — extension leads (retrieved 22.10.2026)
  4. Electrical Safety First — overloading sockets (retrieved 22.10.2026)
  5. London Fire Brigade — cables, fuses and leads (retrieved 22.10.2026)
  6. Scottish Fire and Rescue Service — electrical safety (retrieved 22.10.2026)
  7. BEAMA — extension lead safety checklist (retrieved 22.10.2026)