Everything you need to know about EV charger installations under BS 7671 Section 722. Dedicated circuits, RCD selection, PME earthing restrictions under Regulation 722.411.4.1, earth electrodes, load management, and cable sizing.
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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.
Section 722 of BS 7671 sets the requirements for electric vehicle charging installations. It covers protection against electric shock — including the loss-of-PEN risk on TN-C-S (PME) supplies — RCD protection with DC fault detection for each charge point, disconnection times, and external influences. A4:2026 also allows load curtailment to be considered when assessing maximum demand.
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Section 722 of BS 7671:2018+A4:2026 sets out the particular requirements for the supply of electric vehicles. With the UK government mandate to phase out new petrol and diesel car sales, EV charger installation has become one of the fastest-growing areas of electrical work.
Section 722 covers Mode 2 (portable charger plugged into a domestic socket — not recommended for regular use), Mode 3 (dedicated wall-mounted or post-mounted charger with control pilot), and Mode 4 (DC rapid charger — typically commercial). Most domestic and small commercial installations are Mode 3.
The IET Code of Practice for Electric Vehicle Charging Equipment Installation supplements Section 722 with detailed practical guidance on earthing arrangements, cable selection, load management, and commissioning. Both documents should be read together.
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Regulation 722.312 requires that each EV charging point is supplied by its own dedicated final circuit. This means a separate MCB or RCBO at the distribution board for each charger, with no other loads sharing that circuit.
The circuit must be designed as a continuously-rated load — EV charging can run for hours at the full rated current. No diversity can be applied to a single EV charger circuit.
Regulation 722.312.2.1 adds a further requirement for TN systems: the circuit supplying EV charging equipment must not include a PEN conductor (a combined protective earth and neutral). This means the final circuit wiring must use separate PE and N conductors throughout. On a TN-C-S (PME) installation, the separation of PE and N occurs at the origin of the installation; the EV charging circuit must then be wired with a separate earth conductor and must not re-combine the functions of PE and N at any point downstream.
Regulation 722.531.3 requires RCD protection for EV charging circuits. The type of RCD depends on the charger design. Where the equipment includes a built-in RDC-DD (Residual Direct Current Detecting Device) to BS IEC 62955:2018, a Type A RCD is permitted. Without integral DC leakage detection, a Type B RCD is required. Note: Regulation 722.531.3.101 is a separate requirement covering transformer placement and the one-charger-per-transformer rule — it is not the RCD selection regulation.
If the EV charger has built-in DC fault current detection (to 6mA), a Type A RCD (30mA) is sufficient. Most modern Mode 3 smart chargers include this feature. Check the manufacturer data sheet for confirmation. This is the most common and cost-effective arrangement.
If the charger does not include DC fault detection, a Type B or Type B+ RCD is required. Type B RCDs detect both AC and DC residual currents. They are significantly more expensive than Type A (often over 10 times the cost), which is why chargers with integral DC detection are strongly preferred.
The RCD must be rated at 30mA for additional protection. A Type AC RCD must not be used for EV charging circuits — the minimum is Type A. Using a Type AC RCD could fail to detect DC-component fault currents from the vehicle charger electronics, creating a shock risk.
Regulation 722.411.4.1 is the most significant requirement in Section 722 and the one that causes the most confusion. It restricts the use of PME (TN-C-S) earthing for EV charging installations.
Most UK domestic supplies are TN-C-S (PME). The combined PEN conductor in the DNO supply cable serves as both neutral and earth. If the PEN conductor breaks (open PEN fault), all metalwork connected to the PME earth rises to a dangerous voltage relative to true earth. Inside the building, the main bonding creates an equipotential zone — so the person touching a radiator and a metal socket faceplate is protected because both are at the same potential.
An EV charger installed outside the building (on a driveway, in a car port, or on an external wall) is outside this equipotential zone. A person standing on the ground while touching the vehicle being charged could receive a shock from the voltage difference between the PME earth and true earth. This is why Regulation 722.411.4.1 requires additional earthing measures.
Under A4:2026, the structure of Regulation 722.411.4.1 changed. Indent (a) was deleted (Reg 722.826.3.201 records this deletion). A new indent (iv) was added as an alternative solution. The current A4:2026 regulation provides methods (b), (c), (d), (e), and the newly added (iv) — a PME earthing facility must not be used directly for an outdoor EV charging point protective conductor contact unless one of these alternatives is applied. The Annex to Part 722 has also been redrafted, with updated guidance on method (c) (the voltage-monitoring disconnect device). Always apply the A4:2026 text; earlier editions with indent (a) are superseded.
The regulation requires that where the EV charger is connected to a PME supply and the charging point is accessible from outside the main equipotential zone, an earth electrode must be provided, or one of the other permitted arrangements must be used.
The IET Code of Practice for Electric Vehicle Charging Equipment Installation describes several approaches to satisfy Regulation 722.411.4.1:
Where an earth electrode is used under method (b), the electrode resistance must be sized so that the voltage between the main earthing terminal (MET) and true earth does not exceed 70 V RMS in the event of an open-circuit fault in the PEN conductor of the DNO supply. This is a Section 722-specific design criterion — it is not the generic TT formula (Ra × IΔn ≤ 50 V). Annex 722, Item A722.3 gives guidance on calculating the maximum electrode resistance to satisfy the 70 V RMS limit. The electrode resistance must be measured on site and recorded on the EIC.
For TN-S supplies (separate neutral and earth from the DNO), the PME restriction does not apply because there is no PEN conductor. For existing TT supplies, the charger circuit uses the existing TT earth arrangement. Always verify the earthing system type before designing the EV charger circuit.
A 7.4kW EV charger adds 32A of continuous load to the installation. The typical UK domestic supply is 60A or 80A (100A in newer properties). Adding an EV charger to a property with an electric shower (40A), electric cooker (30A), and other loads can easily exceed the supply capacity.
If the maximum demand assessment shows the supply is insufficient even with load management, the DNO must be contacted to request a supply upgrade before installation.
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The cable for an EV charger circuit must be sized for a continuously-rated 32A load (for 7.4kW) with appropriate correction factors applied:
Elec-Mate's cable sizing calculator handles SWA and twin-and-earth for EV charger circuits. Enter the charger rating, cable run…
Try it free for 7 daysEV chargers installed outdoors are subject to environmental conditions that affect equipment selection and cable routing:
The EV charger installation must be tested and certified in accordance with BS 7671. The testing includes:
An EIC must be issued. The certificate should note the earthing arrangement used for the EV circuit (particularly if a local earth electrode is installed on a PME supply), the RCD type, and the earth electrode resistance. Many installers also complete a specific EV charger certificate alongside the EIC.
Under A4:2026, the Appendix 6 model forms (EIC and EICR) include new fields for recording SPDs (surge protective devices) and AFDDs (arc fault detection devices). Where either device is installed as part of the EV charger circuit, its details must be recorded in the relevant fields. Where no SPD or AFDD is installed, record N/A in those fields. This requirement applies to all EIC certificates issued against BS 7671:2018+A4:2026.
EV charger installation is a high-demand market with strong margins. A typical domestic installation is worth £800 to £1,500 for the electrical work (excluding the charger unit). To install EV chargers, you need competence in the IET Code of Practice for Electric Vehicle Charging (often delivered as a one-day course) and registration with a competent person scheme for Part P self-certification.
Size SWA and twin-and-earth cables for EV charger circuits with the cable sizing calculator. Automatic voltage drop check and derating for burial depth and ambient temperature.
Complete the EIC and EV charger certificate on site. Record earth electrode resistance, RCD test results, and charger details. Instant PDF to the customer.
Section 722.411.4.1 BS 7671:2018+A4:2026 sets out four provisions for PME-supplied EV chargers. Learn cable sizing, earthing rules, and compliance checks.
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