# Why you must not backfeed a house from a socket (myth-busting safety)

> Do not feed a house through a socket from a generator or an EV's V2L adapter. A lead with a plug on both ends — the so-called 'suicide cable' — leaves live pins exposed at the open end, bypasses any changeover so it can back-feed the grid and energise a network or a working linesman, and gives the floating V2L output no earth reference. It is dangerous and the fixed-wiring work it implies is notifiable under Part P. The correct route is a proper **inlet** with a **break-before-make interlocked changeover** and the right earthing arrangement, all designed and proven by test by a competent person. Vehicle manufacturers warn against back-feeding fixed wiring from a V2L outlet.

**Safety frame.** This is education, not an instruction to carry out work. Work connecting V2L equipment to fixed wiring is safety-critical and may be notifiable under Part P. It must be designed, installed, inspected and tested by a competent person to the current edition of BS 7671. Vehicle manufacturers generally do not sanction back-feeding fixed wiring from V2L outlets; follow manufacturer instructions.

## In short

- Never connect a generator or V2L adapter to the house through a socket — a plug-to-plug 'suicide cable' exposes live pins at the open end.
- A socket feed has no changeover, so it can **back-feed** onto the grid — energising network conductors and anyone working on them.
- A floating V2L output fed this way has **no earth reference** — it can pass a socket tester yet give no RCD protection.
- The correct route is a fixed **inlet** + a **break-before-make interlocked changeover** + the right earthing, designed and **proven by test**.
- Adding an inlet, changeover or consumer-unit alteration is normally **notifiable under Part P** (England). Vehicle makers do not sanction back-feeding fixed wiring from a V2L outlet.

**Where this stops:** This explains why the socket shortcut is dangerous and what the correct arrangement is. It is not a wiring recipe — the inlet, changeover and earthing are for a competent person to design, install and test.

> **The one-line answer** — Never feed a house through a socket from a generator or a V2L adapter. Use a fixed **inlet** with a **break-before-make interlocked changeover**, designed and proven by test by a competent person.

## The shortcut people reach for — and why it kills {#do-not-backfeed}

The tempting idea is a lead with a plug on **both** ends: one end into the generator or V2L adapter, the other into a socket in the house, to 'push' power back through the ring or radial into the rest of the board. It is widely called a **'suicide cable'**, and the name is earned. There is no safe version of it.

- **Exposed live pins.** While one end is energised, the pins at the *other* end are live and exposed — a direct contact, electrocution and fire hazard the moment a person or pet reaches the open plug.
- **No changeover, so it can back-feed the grid.** A socket feed has nothing to disconnect the mains. If the source can reach the incoming supply, it energises the network outside the house — including conductors a linesman may be working on believing the line is dead.
- **No earth reference.** A floating V2L output fed this way has no neutral-earth bond, so there is nothing for an RCD to operate against. It can pass a plug-in socket tester and still leave the installation unprotected — the dangerous 'looks fine' case.
- **Gross overload risk.** The plug, the socket and the final-circuit cable are sized to *take* power from the board, not to carry the whole installation's load back through one 13 A accessory.

> **Back-feed endangers people you will never see** — An uncontrolled source connected to house wiring can push power back through the cut-out and onto the local network. That can energise overhead or underground conductors and put a working linesman — or a neighbour — at risk. This is the single most serious reason the socket route is prohibited.

> **§551** (BS 7671, confidence: inference) — The generating-set provisions exist precisely to stop a backup source islanding or back-feeding the public supply uncontrolled. A plug-into-a-socket feed has no anti-islanding measure and no changeover — it defeats the whole framework. _Reference only; standard text not reproduced._

Beyond BS 7671, the network operator's own connection rules (the **ENA Engineering Recommendations**, e.g. G98/G99 for small generators) prohibit connecting a source to the public network without the proper protection and agreement. The exact recommendation locators are referenced here in principle only.

> **Not confirmed:** Exact ENA G98/G99 (or earlier G83/G59) clause locators for the prohibition on uncontrolled source connection — cited in principle only, not by confirmed clause number.

## Why a 'socket tester says it's fine' is a trap

A plug-in socket tester checks that line, neutral and earth are present and in the right places. It does **not** confirm that the earth has a low-impedance return path, nor that an RCD has a reference to operate. A **floating** V2L output — no internal neutral-earth bond — can light a socket tester's 'correct' pattern while offering no fault protection at all. The protection only exists once a single neutral-earth bond is made at the source, and that is a designed, tested arrangement, not something a socket lead provides.

> **Confidence: inference** — A typical EV V2L output (e.g. Hyundai Ioniq 5) is floating — no internal neutral-earth bond. (Reported in field accounts and consistent with the design; behaviour varies by adapter and should be bench-verified before it is relied on. The safe default is to treat the output as floating until proven otherwise. This is contested ground: any floating-V2L-on-PME arrangement is valid only when designed and proven by test by a competent person, and the manufacturer does not sanction this use.)

## It is also notifiable work — not a DIY job

The lawful way to feed a house from a backup source involves fixed wiring: an inlet, a changeover and usually a consumer-unit alteration. In England that is **notifiable under Part P** of the Building Regulations, which means it must be designed, installed, tested and either certified by a registered competent person or signed off by building control. A plug-to-plug lead is an attempt to avoid exactly that — and avoids the protection it provides.

> **Reg 12(6A)** (Building Regulations 2010 (Approved Document P), confidence: verified) — Installing a new circuit or a new/replacement consumer unit in a dwelling is notifiable. A V2L/generator inlet, changeover switch or consumer-unit alteration normally triggers this — so the route is competent-person design, install, test and certify, not a socket lead. Part P is England-specific; Wales, Scotland and Northern Ireland differ. _Reference only; standard text not reproduced._

Vehicle manufacturers reinforce the point from the other direction: they warn against back-feeding fixed wiring from a V2L outlet and do not sanction wiring the output into a home's fixed installation. Treat the V2L socket as an outlet for appliances, not as a feed-in point for the house.

> **Confidence: verified** — The vehicle manufacturer does not sanction feeding fixed wiring from V2L and warns against back-feeding. (Captured in the V2L technical reference at high confidence from manufacturer guidance; the V2L outlet is specified for portable appliance use, not as a source wired into a dwelling's fixed installation.)

## The correct route instead

If you want a backup or load-shifting feed from a generator or an EV's V2L output, the source connects through a **fixed inlet** — a proper inlet socket on the building, wired as a circuit — into a **break-before-make interlocked changeover**. The changeover guarantees the house is connected to *either* the grid *or* the source, never both, so it cannot back-feed the network or parallel the supply. The floating output is then given exactly **one** earth reference — by making it TT in a separate outbuilding, or by an isolation transformer inside the dwelling — so an RCD has something to operate against.

> **§551.4.3.2.1** (BS 7671, confidence: inference) — A switched-alternative or island source needs an independent means of earthing — it must not rely solely on the distributor's earth, which may be disconnected during network maintenance. This is what the correct arrangement provides and the socket feed cannot. _Reference only; standard text not reproduced._

A break-before-make changeover also keeps most domestic V2L out of the paralleling regime — there is never a moment when both sources are connected together.

> **§551.7** (BS 7671, confidence: inference) — Additional requirements apply where a source can operate in parallel with the public supply. A break-before-make interlocked changeover avoids paralleling entirely, which is why it is the right tool — and why a socket feed, which can be live alongside the grid, is the wrong one. _Reference only; standard text not reproduced._

**Figure: V2L / PME changeover earthing circuit.** On a PME (TN-C-S) supply the V2L island gets its own earth reference — the CPC stays continuous, the neutral-earth bond is switched in only on V2L, and a local electrode provides the earth.

_The diagram shows two sources feeding an essential board through a changeover. From the grid, line (L) and neutral (N) arrive at the changeover; the circuit protective conductor (E/CPC) runs continuously to the board and earth bar and is never switched. From the V2L source, L and N arrive at the other side of the changeover. A neutral-earth (N–E) bond is made only when the board is on V2L, providing the floating output its single earth reference. A local earth electrode connects to the earth bar. The point: every source has exactly one neutral-earth reference, and the protective conductor is continuous in both switch states._

The full power-and-control and earthing design — interlocked contactors, the TT-outbuilding route and the indoor isolation-transformer route — is covered in the cornerstone guide and the changeover and earthing pages. The single rule for this page is simpler: the source never reaches the house through a socket.

> **Education, not an instruction to carry out the work** — This is education, not an instruction to carry out the work. Installation work of this kind is notifiable and must be designed, installed and tested by a competent person to the current edition of BS 7671. The floating-V2L-on-PME earthing arrangement is contested and valid only when designed and proven by test; the vehicle manufacturer does not sanction this use.

### How this is made and proven compliant

**What governs it:** BS 7671 §551 (low voltage generating sets — anti-islanding, back-feed prevention) and §551.4.3.2.1 (independent means of earthing for a switched-alternative/island source); BS 7671 §722.411.4.1 where a vehicle output is wired into the installation on a PME (TN-C-S) supply (open-PEN protective measures); Building Regulations 2010 / Approved Document P (England) — notifiable fixed-wiring work; devolved nations differ

**Who may do it:** Design, installation, inspection and testing by a competent person. Adding an inlet circuit, a changeover switch or altering the consumer unit is normally notifiable under Part P (England); Wales, Scotland and Northern Ireland operate different regimes.

**How compliance is demonstrated:** A fixed inlet socket plus a break-before-make interlocked changeover — never a plug-to-plug lead into a socket; Initial verification to BS 7671 Part 6 with an Electrical Installation Certificate, and Part P notification/certification; RCD operation proven by test in both grid and source modes; confirm no path exists to back-feed the public supply; Confirm the actual V2L adapter's neutral-earth behaviour on the bench before relying on it as a source

## FAQ

### Why is a plug-to-plug 'suicide cable' so dangerous?

While one end is energised, the pins at the open end are live and exposed — a direct electrocution and fire risk. It also has no changeover, so the source can back-feed onto the grid and energise network conductors and anyone working on them. There is no safe version of it.

### If a socket tester shows the wiring is correct, isn't a socket feed safe?

No. A socket tester checks that line, neutral and earth are present and in the right places — not that an RCD has an earth reference to operate against. A **floating** V2L output can light the 'correct' pattern and still give no fault protection at all.

### What is the correct way to feed a house from a generator or V2L?

A fixed **inlet** wired as a circuit, feeding a **break-before-make interlocked changeover**, with one designed earth reference for the source (TT in an outbuilding, or an isolation transformer indoors). It must be designed and proven by test by a competent person.

### Do I really need an electrician — can't I just plug in?

You need a competent person. Adding an inlet, a changeover switch or altering the consumer unit is normally **notifiable under Part P** in England (Wales, Scotland and Northern Ireland operate different regimes), so it must be designed, installed, tested and certified — not done with a plug-in lead.

### Does the car maker allow back-feeding the house from V2L?

No. Vehicle manufacturers warn against back-feeding fixed wiring from a V2L outlet and do not sanction wiring it into a dwelling's fixed installation. The V2L socket is for appliances, not as a feed-in point for the house.

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_Author: Martin — qualified UK electrician (BEng Mech Eng; vehicle mechanic)._
_Last reviewed: 14 June 2026. Written against: BS 7671:2018 + A4:2026._
_Status: reviewed. General information, not project-specific design advice._
_[How we source this](/methodology) — evidence hierarchy, confidence flags and source policy._

## Sources

1. BS 7671:2018+A4:2026 — Requirements for Electrical Installations (IET/BSI) — https://electrical.theiet.org/bs-7671-18th-edition-wiring-regulations/about-bs-7671/ (cited by clause only; standard text not reproduced)
2. IET — Amendment 4 updates to the 18th Edition — https://electrical.theiet.org/amendment-4-updates-to-18th-edition
3. Approved Document P — Electrical safety (Building Regulations, England), 2013 edition (GOV.UK) — https://www.gov.uk/government/publications/electrical-safety-approved-document-p (Crown copyright, Open Government Licence; Part P is England-specific)
4. Energy Networks Association — Engineering Recommendations G98 / G99 (connection of generation) — https://www.energynetworks.org/industry-hub/resource-library/ (referenced in principle for the prohibition on uncontrolled source connection; exact locators not confirmed here)
5. V2L Workshop technical reference (internal) — verified design facts, manufacturer back-feed caveat and confidence flags