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Socket tester buying guide

Updated: 22 October 2026

You have just replaced a socket and you want something that says the wiring is right. A socket tester buying guide for a UK 13 A outlet starts with earth fault loop impedance, not with stars or a colour screen. Electrical Safety First, in Best Practice Guide 8 (February 2015), splits plug-in testers by whether they show that loop. Every listing in our [socket tester comparison](/hub/measuring-equipment/socket-tester) is the simple class: lamps, a tone or an LCD, and no loop band. Updated on 21 October 2026 by the Products Compared editorial team. A qualifying purchase can earn us a commission at no extra cost to you.

You have just replaced a socket and you want something that says the wiring is right. A socket tester buying guide for a UK 13 A outlet starts with earth fault loop impedance, not with stars or a colour screen.

Our top picks

Martindale Martindale BZ101 Buzz-It

Best overall

Martindale Martindale BZ101 Buzz-It
8.4/10about £17.34
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Kewtech Kewtech KEWCHECK 103

Alternative

Kewtech Kewtech KEWCHECK 103
8.0/10about £22.00
View offer
KAIWEETS KAIWEETS HT106E

Best value

KAIWEETS KAIWEETS HT106E
6.9/10about £11.99
View offer
On this page
  1. 1.Three kinds of socket tester
  2. 2.What the lamps cannot see
  3. 3.What you can still buy a simple plug for
  4. 4.When this set is the wrong shelf

Three kinds of socket tester

A simple socket tester is a BS 1363 plug that shows whether line, neutral and earth appear to be on the expected pins. An advanced plug adds a band for earth fault loop impedance. Martindale's EZ165 and EZ365 do that, and neither is in this amazon.co.uk set. A voltage screen or an RCD button does not change the class. Only the loop display does. Here the BZ101 is £17.34 and the KEWCHECK 103 is £22.00. The best socket tester UK page names which simple plug fits that smaller job.

What the lamps cannot see

On TN-C-S, the usual UK house supply, neutral and earth join at the substation, so a swap at the socket still looks like earth. None of the 11 listings has a touch-pad, so most also miss an incoming line and PEN reversal. An open ring, a loose terminal or poor insulation can sit behind a correct pattern, including on an extension lead. The Health and Safety Executive's electricity FAQ says a socket tester can indicate safe when the socket is not. Calling an RCD trip a timed test is a separate limit, on the socket tester RCD test page.
Martindale Martindale BZ101 Buzz-It

Testsieger

Martindale Martindale BZ101 Buzz-It
8.4/10about £17.34
View offer

What you can still buy a simple plug for

A simple plug is still worth a first look after you fit a socket or before you trust a new lead. Read only that tester's legend. A buzzer is a fuse finder when you can hear it at the consumer unit. Motorhome users can check hook-up polarity and still cannot see a PME supply reversal. Pay for a named chart and a tone before a screen. The QUIWILL file mixes 120 V with 260 V, and the Grosion listing prints 10 g, so those rows are conflicts rather than bargains.

When this set is the wrong shelf

Leave this set for a loop band, a recorded disconnection time, or verification of new work. Best Practice Guide 8 says a plug-in tester is not the verification for a new, repositioned or replaced socket. That work sits under BS 7671. The same stop applies to a tingle, an RCD that will not reset, or a consumer-unit change. A reading outside 216.2 V to 253 V on a proper meter at the incoming terminals is a distribution question. If you need the earth path in ohms, stop shopping inside this category.

Common questions

Is a cheap three-light tester enough for a house?
A three-light plug can show a first-look pattern on a live BS 1363 socket, which helps when you want to see whether an outlet is energised or a new lead looks swapped. It is not enough to decide that the earth will disconnect a fault. Simple testers in the 2015 guide stayed quiet at 22 ohms and at 218 ohms. Use it as a pattern check, and call a competent person for anything you would put on a certificate.
What is the difference between a simple and an advanced socket tester?
A simple tester shows lamps, a tone or a voltage digit. An advanced socket tester also shows earth fault loop impedance as a band or a number. The Martindale EZ365 is that second class, and it is not one of the products compared here. An LCD around £12 does not become advanced because the screen looks busier than three lamps.
Why can the lamps say earth is present when the earth is poor?
The lamp looks for continuity above a high threshold, not for a low loop impedance. The BZ101 data sheet calls open earth at about 50 kilohms. The 2015 guide records simple testers that still looked acceptable at 218 ohms and that might not warn until the impedance could exceed 20,000 ohms. Earth present on a legend can still be a useless earth.
Do I need a professional loop meter to check one socket?
You need a professional instrument when the result has to satisfy BS 7671, for example on a new circuit or a replaced socket that will be certified. For one existing socket, where you only want that model's pass pattern, a simple plug is the usual check, and it still does not measure the earth path. One socket does not turn the plug into a loop meter.
Are the LCD plugs in the £12 band a higher class than the Martindale buzzer?
No. The HT106E at £11.99 and the HT107E at £12.97 add a digit and, on those listings, an RCD button. They do not show a loop band. Reviews dispute the voltage against a multimeter, sometimes by about 20 V. The BZ101 is a simple tester too. Its advantage is a published open-earth threshold, not a higher class.
Can any plug in this set see a neutral and earth swap?
No. On TN-C-S the two conductors are common at the substation, so the swap looks like a normal earth. Martindale states that earth-neutral reversal is not detectable, and Best Practice Guide 8 agrees. A correct pattern does not clear that fault, on the BZ101 or on a budget lamp plug.
Should the 2015 under £20 line be used as today's price?
No. That line is a description in Best Practice Guide 8, Issue 2, February 2015. It is history, not a current cap. In this amazon.co.uk set, simple plugs run from about £7.99 to £24.55, and the two named buzzers are £17.34 and £22.00. Advanced loop plugs were roughly £52 to £68 including VAT on specialist sites, outside this grid.

Related pages

How to use a socket tester

Socket tester

Best socket tester UK: a published limit, not stars

Socket tester RCD test: a trip is not a timed result

Socket tester lights meaning: use this legend only

Sources

Public UK sources from the research digest, last checked on 21 October 2026. Shelf prices and star lines are the amazon.co.uk figures captured with these eleven listings. The price bands are this set, not a market average.

  1. Electrical Safety First, Best Practice Guide 8, Issue 2 (February 2015) (retrieved 21 October 2026)
  2. HSE: electricity FAQ (retrieved 21 October 2026)
  3. ESQCR 2002, regulation 27 (retrieved 21 October 2026)
  4. SP Energy Networks: voltage changes (retrieved 21 October 2026)
  5. Martindale BZ101 data sheet (retrieved 21 October 2026)
  6. Kewtech KEWCHECK 103 (retrieved 21 October 2026)
  7. BEAMA RCD handbook 2018 (retrieved 21 October 2026)
  8. amazon.co.uk, Martindale BZ101 listing (retrieved 21 October 2026)