Why you shouldn’t put customer wiring inside a meter box

It’s increasingly common to see customer wiring installed inside domestic meter boxes — EV charger supplies, isolators, Henleys, small distribution enclosures, and various “it’ll do” junctioning. The reasoning is usually practical: the space exists, it’s external, and in many cases the homeowner owns the cabinet.

However, this practice causes repeated problems — not because of personal preference or “what inspectors like”, but because meter cabinets are not accepted or managed as spaces for customer wiring, and because real electrical shortcomings often appear once they’re used that way.

If you’re planning an EV charger supply or any external electrical work in Colchester or North Essex and want it designed and installed properly (without “meter box bodges”), bookings are via Gray Logic Electrical.

1) Meter cabinets aren’t accepted as customer wiring spaces (and this is not a BS 7671 rule)

It’s important to be clear from the outset:

There is no regulation in BS 7671 that explicitly forbids customer wiring inside a meter cabinet.

However, that does not mean meter cabinets are accepted or suitable spaces for customer wiring — and the reason has nothing to do with opinion.

Where the restriction actually comes from

Domestic meter cabinets sit in a boundary space between the customer installation and the electricity supply network. They’re governed in practice by:

• DNO / supplier safety duties, and
• meter operator access requirements,

not by BS 7671 design rules.

Industry and government guidance is explicit (see the references in the technical note). The practical takeaway is simple: metering equipment needs clear, safe access, and the meter cabinet is treated as “metering space”, not a general-purpose customer wiring enclosure.

Why “the customer doesn’t care what the DNO says” isn’t a defence

From a customer’s perspective, this usually only becomes relevant later — when a smart meter is fitted, when an upgrade is requested, when the cut-out/service head needs work, or when a safety issue arises. At that point, if the metering space is considered unsafe or unsuitable, work simply won’t proceed until it’s resolved.

2) Why ownership doesn’t make an enclosure “suitable”

A common argument is that the homeowner owns the meter cabinet, therefore it can be used as they wish. Ownership doesn’t change suitability.

A better way to think about it is this: owning a weatherproof storage box doesn’t make it an electrical enclosure. If it hasn’t been designed and declared to provide the required protection for live parts, you can’t treat it as though it has.

That aligns with general BS 7671 principles around equipment being suitable for the application and installed in accordance with intended use and instructions (e.g. Regs 133.1.1 and 134.1.1).

3) Supplier isolators don’t create permission

Supplier isolators are often fitted inside meter cabinets and are frequently used as justification for adding customer equipment. They don’t create permission.

Supplier equipment sits under supplier authority as part of the metering arrangement. Customer-installed equipment does not share that status, even if it looks similar.

4) Where BS 7671 becomes relevant (accurately)

BS 7671 doesn’t care that a cable passes through a meter cabinet. It becomes relevant when compliance relies on conditions in that space. Typical triggers include:

• Basic protection being provided by barriers/enclosures (Regs 416.2, 416.2.1, 416.2.4)
• Reliance on degree of protection (IP) for accessories/terminations (linking back to suitability, Reg 133.1.1)
• Mechanical protection of wiring systems (Reg 522.8.1) and avoiding mechanical strain at terminations (Reg 522.8.5)
• Sound connections (Reg 526.1)
• Earthing / PE integrity where relied upon (Chapter 54; and 411.3.1.1 where applicable)

The key question BS 7671 asks isn’t “is it a meter box?”. It’s:

What is providing the protection you’re relying on, and is it suitable?

5) Meter tails and “basic insulation” — what the real issue is

Meter tails are typically double insulated. The usual problem is not “tails exist in a meter box” — it’s what often happens at terminations:

• insulation stripped back too far
• basic insulation visible outside an enclosure
• poor entry/retention arrangements leaving conductors unsupported or vulnerable

Once stripped insulation or exposed basic insulation exists in a space, the discussion returns to basic protection by barriers or enclosures (Regs 416.2 series), suitability (Reg 133.1.1), workmanship and intended use (Reg 134.1.1), mechanical strain/support (Reg 522.8.5), and soundness of connections (Reg 526.1).

6) EV charger supplies: SWA termination and armour earthing

EV work is where meter-box installs most often go wrong.

A common pattern is: SWA EV feed enters the meter cabinet, the SWA is terminated into a small customer enclosure inside, and the termination is done with a stuffing gland rather than a BW/CW type armour gland.

a) Mechanical termination and strain relief

Stuffing glands may grip the sheath, but they don’t properly terminate the armour. That can leave terminations mechanically weak and put stress onto inner conductors.

Relevant regs/principles: avoiding mechanical strain and providing appropriate support (Reg 522.8.5), sound connections (Reg 526.1), and proper workmanship (Reg 134.1.1).

b) Armour earthing (especially with plastic EV chargers)

Many EV chargers are plastic. In practice that often means the armour isn’t properly dealt with at the EV unit end. If it’s also not correctly terminated at the supply end, the armour may be floating.

Under a core-to-armour fault, that can affect fault conditions and what clears what. The design must ensure the protective measures are effective, and the installation must verify this by test.

7) The correct approach

If customer equipment is required near the intake:

1. Install a separate, purpose-designed enclosure rated for the environment (Reg 133.1.1).
2. Keep customer wiring and terminations out of the meter cabinet unless there’s a clear reason and protective measures are not being compromised.
3. Terminate SWA correctly (correct gland, correct earthing method, tested and verified) (Reg 526.1; Reg 522.8.5; Chapter 54).
4. Leave the meter cabinet for metering equipment only (aligns with published guidance and avoids access disputes).

Takeaway

This isn’t about claiming BS 7671 “bans” customer wiring in meter cabinets — it doesn’t.

It’s about recognising two realities:

• the metering space is intended and enforced as metering-only (industry/government guidance), and
• BS 7671 becomes relevant when protection, IP performance, termination integrity or earthing relies on the conditions inside that space.

The simplest, cleanest solution remains: Add a proper enclosure. Don’t repurpose the meter cabinet.

References

• IET Wiring Matters (Sep 2024): External consumer units for EVs in a domestic environment (includes ENA statement) — Link
• UK Government: Smart Metering Guidance for New Builds (PDF) — Link
• GTC: Technical Guidelines – Electricity (PDF) — Link