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Plug in energy monitor or CT clamp

Updated: October 2026

The kettle has a plug. The cooker does not. Both get called an energy meter, and buying the wrong one wastes the afternoon. A plug in energy monitor or CT clamp is a split on what the load is, not on which brand has more stars. If you can unplug it, use a socket meter. If you cannot, you need a clamp or a hardwired monitor and someone competent, not a braver hour with the consumer unit open. Our [energy meter comparison](/hub/measuring-equipment/energy-meter) lists both shapes. This page only decides between them. DIN rail, tariffs and trade billing sit in the [buying guide](/hub/measuring-equipment/energy-meter/sub/energy-meter-buying-guide).

The kettle has a plug. The cooker does not. Both get called an energy meter, and buying the wrong one wastes the afternoon.

Our top picks

SONOFF SONOFF POWCT clamp power meter

Best overall

SONOFF SONOFF POWCT clamp power meter
9.0/10about £29.91
View offer
Tapsin Tapsin energy monitor plug

Rank 2

Tapsin Tapsin energy monitor plug
9.0/10about £13.99
View offer
Awootsv Awootsv PM04UK-1 power meter plug

Preis-Tipp

Awootsv Awootsv PM04UK-1 power meter plug
9.0/10about £11.99
View offer
On this page
  1. 1.What a plug can see
  2. 2.What a clamp can see
  3. 3.Who fits it
  4. 4.Which listing sits on which side

What a plug can see

A plug-in meter occupies a BS 1363 socket. It sees that appliance, or one extension. The plug does not tell you the home's share. Ofgem's example standing charge is 54.83p a day, and no socket meter here adds that line. At 230 V a 13 A fuse is about 2,990 W. A printed 3,680 W is 16 A. A renter who cannot touch the board stays with a plug.

What a clamp can see

A clamp sits on one cable. The POFET bullet says one direction only, so a solar title does not measure export. The POFET title says 80 A and a bullet says a 10 mm opening. A UK review says 25 mm tails would not close. The SONOFF states 100 A. Its relay is a 2 A dry contact for a contactor, not a 100 A switch.
SONOFF SONOFF POWCT clamp power meter

Testsieger

SONOFF SONOFF POWCT clamp power meter
9.0/10about £29.91
View offer

Who fits it

You fit a plug by using a sound socket. A clamp on the consumer unit is not. In England a new circuit or a replacement consumer unit is notifiable. That note is not the rule for Scotland or Northern Ireland. If the tails are 25 mm and the clamp is 10 mm, stop. The Emporia Vue 3 is £109.99 and hardwired. A UK review says the figures were in dollars. A competent person fits it.

Which listing sits on which side

The top pick among plugs is the Tapsin at £13.99, and the best value is the Awootsv at £11.99. Those labels apply only if the load has a plug. POFET at £16.99 needs a cable that fits 10 mm. SONOFF at £29.91 is the larger stated current, fitted by a competent person. Choose a plug when you can unplug the appliance. Button-level use is how to use an electricity usage monitor. A qualifying purchase can earn a commission at no extra cost to you. Products Compared set this split from the listings on 16 October 2026, without a lab test.

Common questions

I want the whole bill. Is a plug enough?
No. A plug sees one socket or one extension. The bill adds every circuit and the standing charge. Ofgem's example for England, Scotland and Wales in this quarter is 26.32p per kWh and 54.83p a day on Direct Debit, and the daily line never appears on these plugs. Use a plug to learn one appliance. Use the supplier display, or a properly fitted whole-home monitor, for the house.
The kettle has a plug. Do I still need a clamp?
No. Put a socket meter between the kettle and the wall. A clamp belongs on a cable you cannot unplug. Opening the consumer unit to price a kettle adds risk and does not improve the reading. Stay under the 13 A fuse, about 2,990 W at 230 V, whatever a 3680 W headline says.
Can I clip the clamp on without an electrician?
Not as a DIY guide from this page. A sound socket is yours to use. The consumer unit, the tails and a new circuit are electrical work. In England that work can be notifiable. If you are a renter and the agreement says you cannot touch the board, you are a plug-in buyer. A 10 mm clamp that will not close on 25 mm tails is not a job you finish with more force.
Will a one-direction clamp see solar export?
The POFET bullet says one direction only, and not bidirectional solar or battery measurement unless otherwise specified. Do not buy it to see export. The SONOFF bullets claim solar-panel monitoring, and a UK review compared it with an inverter, which is still not the supplier's export meter. Read the direction claim on the listing you are about to order.
Why does the POFET title say 80 A if the clamp is 10 mm?
Both lines are on the listing. The title says 80 A. A bullet says the opening is 10 mm and will not fit larger mains cables. A UK review says 25 mm tails would not close. The 80 A figure does not widen the jaws. If your cable is larger than 10 mm, this clamp is the wrong listing, however many of the 380 reviews you read.
Is the SONOFF a switch or only a meter?
It is a meter with a small relay. The bullet says a dry contact rated 2 A, used with a contactor to switch a load. The 100 A figure is the stated measuring limit, not the current that relay can break. Do not use the POWCT as a 100 A switch. Fitting the meter is still electrical work.
Does the in-home display already do this?
It does the house, if your supplier has fitted a smart meter, and it does not split out the kettle. Which? separates that display from a plug-in monitor. A clamp is a third tool, for one cable, and it is not a replacement for the supplier meter. If the in-home display already answers the question you have, you do not need either product from this page.

Related pages

Best plug in energy monitor

Energy meter

Electricity usage monitor buying guide for UK homes

How to use an electricity usage monitor, step by step

How to calculate appliance running cost in a UK home

Sources

Public UK sources on the price cap, trade meters, notifiable electrical work and competence. Shelf prices, stars and review counts are the amazon.co.uk lines in the twelve listings dated 16 October 2026. Prices move.

  1. Ofgem, energy price cap 1 October to 31 December 2026 (retrieved 16 October 2026)
  2. Ofgem, energy price cap unit rates and standing charges (retrieved 16 October 2026)
  3. GOV.UK, Measuring Instruments Regulations 2016, Great Britain (retrieved 16 October 2026)
  4. Measuring Instruments Regulations 2016, SI 2016/1153 (retrieved 16 October 2026)
  5. GOV.UK, building work, replacements and repairs (retrieved 16 October 2026)
  6. HSE, electrical safety introduction (retrieved 16 October 2026)
  7. Electricity at Work Regulations 1989, regulation 16 (retrieved 16 October 2026)
  8. Which?, energy monitors and measuring power use (retrieved 16 October 2026)