TECHNICAL GUIDE

Electrical Work Around Smart Meters — UK Electrician Guide

A complete guide to electrical work in properties with SMETS2 smart meters — consumer unit upgrades, meter tails, safe isolation, IHD devices, DNO responsibilities, and Part P certification.

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8 min readUpdated 2026-05-18Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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Key Takeaways

  • 1Smart meters (SMETS2) belong to the energy supplier and are installed and maintained by them. Electricians must not open, alter, or remove smart meters without specific written authorisation from the energy supplier.
  • 2Meter tails — the cables between the meter and the consumer unit — are the responsibility of the property owner (in most cases), not the DNO or energy supplier. An electrician can replace or upgrade meter tails, but must safely isolate at the cut-out fuse first.
  • 3Consumer unit replacements with a smart meter already installed are common and straightforward. The electrician works on the consumer unit side (load side) of the meter. The meter itself is not affected.
  • 4The main fuse (cut-out fuse) in the service head belongs to the DNO and must not be removed without the DNO's authorisation. If the fuse needs to be removed for safe isolation during consumer unit work, the DNO must be contacted in advance.
  • 5SMETS2 meters support remote reading, remote switching, and load limiting by the energy supplier via the Smart Metering Wide Area Network (WAN). An electrician working near the meter must not inadvertently interfere with the communications module.
  • 6All new circuits installed in a property with a smart meter must still be notified under Part P Building Regulations and certified with the appropriate electrical certificate, exactly as for a property without a smart meter.
01 · Technical Guide

SMETS2 Smart Meter Overview

Second-generation smart meters (SMETS2) are now the standard installation across Great Britain. Understanding the SMETS2 architecture helps electricians know which parts of the metering system they can and cannot interact with.

  • Service head (cut-out) — owned by the DNO. Contains the main fuse (typically 60A or 100A). Cannot be accessed without DNO authorisation.
  • Smart meter — owned by the energy supplier. Measures consumption and communicates with the DCC via the Wide Area Network (WAN) using GPRS or mesh radio. Electricians must not open or alter the meter.
  • Meter tails — the cables from the service head to the meter and from the meter to the consumer unit main switch. Typically 16mm\u00b2 or 25mm\u00b2 singles. Owned by the property owner (in most cases). Can be replaced by an electrician with DNO authorisation for cut-out isolation.
  • Consumer unit (distribution board) — owned by the property owner. Electricians work on this side. Not affected by the smart meter.
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02 · Technical Guide

What Electricians Can & Cannot Do Near a Smart Meter

The boundary between energy supplier/DNO equipment and the customer installation is critical. Crossing it without authorisation is illegal and dangerous.

  • Permitted: All work on the consumer unit and all circuits downstream of the main switch. Replacing meter tails (with DNO authorisation for cut-out isolation). Installing new circuits, adding socket outlets, and replacing accessories throughout the property.
  • Not permitted without authorisation: Opening, altering, or removing the smart meter. Removing the cut-out fuse. Interfering with the communications hub or Home Area Network (HAN) equipment. Relocating the meter.

For guidance on safe isolation procedures, see our electrical fault finding guide.

03 · Technical Guide

Consumer Unit Upgrades with Smart Meters Installed

A consumer unit replacement is one of the most common electrical jobs in properties with smart meters. The presence of a smart meter does not significantly change the procedure, but there are a few important considerations.

  • Isolation at the main switch — in most consumer unit replacements, isolation is achieved at the consumer unit main switch, which is on the load side of the meter. The smart meter remains energised throughout — only the consumer unit and circuits beyond the main switch are de-energised.
  • When the cut-out fuse must be removed — if the meter tails need to be replaced, or if access to the back of the consumer unit requires removal of the tails, contact the DNO in advance to arrange authorised removal of the cut-out fuse. Do not remove the cut-out fuse unilaterally.
  • IHD reconnection — after restoring the supply, check that the in-home display (IHD) is showing live data. If it has lost connection, follow the energy supplier's reconnection procedure. This is typically automatic within a few minutes.

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04 · Technical Guide

Meter Tails & Safe Isolation

Meter tails are the large-section cables that carry the full supply current between the service head, the meter, and the consumer unit. They require careful handling and DNO coordination.

  • Typical specification — meter tails for a 100A domestic supply are typically 25mm\u00b2 singles (line and neutral) with a 16mm\u00b2 earth. For supplies up to 60A (less common), 16mm\u00b2 tails may be adequate. Check the supply current rating and calculate the appropriate cable size.
  • DNO authorisation for cut-out removal — before replacing meter tails, contact the local DNO (UK Power Networks, National Grid ED, SP Energy Networks, etc.) to request authorised removal of the cut-out fuse. They will provide a specific time and procedure. Lead times vary — allow at least 5 to 10 working days for the appointment.
  • Colour-coding of meter tails — meter tails in the UK use the current harmonised colour code: brown for line, blue for neutral, green-yellow for earth. Where old red/black tails are found, re-identification with correct colour sleeving is required under BS 7671 Regulation 514.4.2 when the tails are replaced.

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05 · Technical Guide

In-Home Display (IHD) Devices

The in-home display (IHD) is a wireless device supplied by the energy supplier that shows real-time gas and electricity consumption data. It communicates with the smart meter via the Home Area Network (HAN).

  • Relocating the IHD — the IHD can be moved anywhere within the wireless range of the communications hub (typically up to 30m inside a building). No electrical work is required — the IHD is battery-powered or uses a small USB/mains adapter.
  • IHD lost connection after electrical work — if the supply was interrupted during electrical work, the IHD may need time to reconnect to the HAN. Allow 10 to 15 minutes after restoring supply before concluding that there is a fault. If the IHD does not reconnect, contact the energy supplier's smart meter support line.
06 · Technical Guide

Part P Compliance for Work Near Smart Meters

The presence of a smart meter has no effect on Part P Building Regulations requirements. All notifiable electrical work must still be certified in the usual way.

  • Electrical Installation Certificate (EIC) — required for new circuits and consumer unit replacements. Must include test results from all circuits: insulation resistance, continuity, polarity, RCD times, and loop impedance.
  • Minor Works Certificate (MWC) — for additions to existing circuits. Issued after testing the addition and confirming compliance of the existing circuit it is added to.

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How to Safely Work Near a Smart Meter — Step by Step

Follow this procedure when carrying out electrical work in a property with a SMETS2 smart meter.

1

Confirm the meter type and supply arrangement

Before starting work, identify whether the property has a SMETS1 or SMETS2 meter (check for a communications module or HAN hub attached to or near the meter). Note the supply arrangement: single-phase or three-phase; overhead or underground supply; TN-S, TN-C-S, or TT earthing system. Confirm who is responsible for the cut-out fuse — this is always the DNO.

2

Notify the DNO if cut-out fuse removal is required

If your work requires safe isolation at the cut-out fuse (for example, replacing meter tails or the main switch), contact the DNO in advance. UK Power Networks, National Grid ED, and other DNOs have a process for authorised fuse removal. They will either send an engineer or issue a formal permit. Never remove a DNO cut-out fuse without authorisation — it is an offence under the Electricity Act 1989.

3

Isolate the consumer unit circuit you are working on

For most electrical work in the property (adding circuits, replacing socket outlets, installing new lighting), you only need to isolate the relevant circuit MCB at the consumer unit. You do not need to touch the meter or the cut-out fuse. Prove dead with an approved voltage indicator before proceeding.

4

Complete the consumer unit upgrade or new circuit installation

For a consumer unit replacement, connect the new CU to the existing meter tails (line, neutral, earth). Ensure the main switch in the new consumer unit is rated for the supply current (typically 100A for domestic). Test all circuits per BS 7671: insulation resistance, continuity, polarity, RCD trip times, and loop impedance.

5

Check smart meter communication is not affected

After completing work, check that the smart meter's in-home display (IHD) is still communicating. If the IHD has lost connection, this may simply require it to reconnect to the home WAN (HAN) network — typically within a few minutes. If the meter itself has lost comms, contact the energy supplier's smart meter support team. Do not attempt to reconnect the meter communications module yourself.

6

Issue the correct certificate

Issue a Minor Works Certificate for additions to existing circuits, or an Electrical Installation Certificate for a new consumer unit or new circuits. The presence of a smart meter does not change the certification requirements. Use the Elec-Mate app to generate and share the certificate instantly.

Smart Meter Electrical Work — Frequently Asked Questions

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