IET EV charging code

The IET Code of Practice for EV Charging Equipment Installation explains how to plan, design, install, verify and maintain EV charging installations. It turns the broader requirements of BS 7671 into EV-specific engineering guidance for homes, workplaces, public sites, fleets and rapid-charging installations.

As at 22 July 2026, the 5th Edition, published in 2023, remains the edition offered by the Institution of Engineering and Technology. It is the right starting point, but it is not the only document an installer needs. BS 7671 and network guidance have changed since the book was prepared.

Guidance rather than a replacement for BS 7671

The Code of Practice is an IET guidance publication, not BS 7671 itself and not a substitute for the current wiring regulations. It explains practical issues that arise specifically with vehicle charging, but the electrical installation still has to meet the applicable edition of BS 7671.

Its status can also change with the route through which it is used:

• Approved Document S in England directs relevant building work to BS 7671 and the IET Code of Practice
• Office for Zero Emission Vehicles grant specifications require installations through the named schemes to follow it
• contracts, specifications, insurers or competent-person schemes may make compliance with it an express project requirement

This is different from saying that every sentence in the book is itself legislation. The applicable Building Regulations, electricity-safety rules, product regulations and contractual terms remain separate.

The current-edition trap

The 5th Edition was published as aligned with BS 7671:2018+A2:2022 and the guidance then current in ENA Engineering Recommendation G12/4. Both references have since moved on.

As at 22 July 2026:

• BS 7671:2018+A4:2026 was published on 15 April 2026 and may be used immediately
• the previous A2:2022+A3:2024 version is scheduled to be withdrawn on 15 October 2026
• ENA lists G12 Amendment 1 to Issue 5, published in June 2026, as the current PME recommendation

The book has not stopped being useful. It means a designer should use its EV-specific method and explanations alongside the edition of BS 7671 against which the work will be designed and certified, plus the current ENA and DNO requirements. A regulation number or earthing option copied from the 2023 book should not be assumed to be the final current wording.

What the Code covers

The 5th Edition covers the work around the charger, not just the charge point on the wall. Its main subjects include:

• site assessment and planning
• maximum demand, supply capacity and load management
• earthing and protection against electric shock
• circuit and cable design
• residual current protection and DC residual-current detection
• charger location, accessibility and physical protection
• telecommunications and auxiliary control cabling
• fire-safety considerations
• inspection, testing and use of vehicle simulators
• DNO notification
• Mode 4 DC charging and pantograph systems
• inductive charging
• vehicle-to-grid and vehicle-to-home arrangements

The design can therefore change even when the chosen charger stays the same. Supply type, earthing arrangement, available capacity, cable route, parking position and whether the vehicle is considered indoors or outdoors all affect the installation.

Supply capacity and load control

The designer assesses the existing installation and the maximum demand after charging is added. That assessment covers the service equipment, consumer unit or distribution board, protective devices, circuit route and other significant loads.

A charger does not automatically require a supply upgrade. Load curtailment or dynamic load balancing may reduce charging power when the rest of the property is using more electricity. The current BS 7671 position and the actual control arrangement must be used in the maximum-demand assessment. A marketing claim that a charger has a CT clamp is not, on its own, the completed design.

The DNO process depends on the proposed demand, the existing connection and any generation or bidirectional operation. The installer should use the current ENA application or notification route and the relevant network operator’s requirements rather than relying on a threshold copied from an older guide.

Earthing and an open PEN conductor

Many British homes have a TN-C-S supply using protective multiple earthing. A broken combined protective-earth-and-neutral conductor on the public network can raise connected metalwork above true earth potential. A person touching a vehicle outdoors can then bridge that potential while standing on the ground.

BS 7671 Section 722 and the Code of Practice address how the charging installation is protected from that risk. The appropriate solution depends on the supply, the charger, the site and the current standards. It can involve protective equipment that disconnects the relevant conductors, a correctly designed earthing arrangement or another permitted engineering solution.

The exact list should be taken from the edition of BS 7671 used for the design, not reproduced from memory. The ENA’s current G12 document also matters where a connection is made to a DNO or IDNO network. ENA states that its requirements take precedence over BS 7671 for those network connections and may be supplemented by the individual network company’s own PME rules.

IET 01:2024 now provides a standardised approach for open-PEN protection devices, whether separate or integrated into charging equipment. The June 2026 amendment to G12 Issue 5 added open-PEN protection devices, referenced IET 01 and clarified PME requirements for street equipment and EV charge points. Product literature should therefore identify the protective function and standard rather than merely use a broad phrase such as “PEN protection included”.

RCDs and fault protection

An EV can introduce DC residual current that affects how an upstream residual current device operates. The protection design has to consider the charge point’s internal detection, the external RCD, coordination with upstream devices and the manufacturer’s instructions.

The familiar shorthand that a particular charger “only needs a Type A RCD” is not a complete design statement. The installer needs evidence of the charger’s residual-current detection, its standard and ratings, then selects and verifies the protective devices under the current BS 7671 requirements.

The Code also covers testing on the vehicle side of Mode 3 equipment. A vehicle simulator allows the installer to establish charging states and access test points without using a car as test equipment. Test results still need to be recorded on the correct electrical certificate.

Cable, circuit and communications design

The charging circuit is designed for its load, route, installation method, grouping, ambient conditions, voltage drop and fault protection. An outdoor or buried route also needs suitable environmental and mechanical protection. There is no universal cable size for every 7 kW charger, and a preferred cable size copied from another installation is not a calculation.

Smart chargers can also need Ethernet, control-bus, current-transformer or other auxiliary cabling. The 5th Edition added guidance on this part of the installation. The route and segregation of those cables should be designed at the same time as the power circuit, particularly where a charger relies on load control or remote operation.

Product rules are separate

The EVs (Smart Charge Points) Regulations 2021 govern the sale of covered private charge points in Great Britain. They deal with smart functionality, default controls, data, security and information supplied at sale.

Those product rules do not certify the installed circuit. Equally, an electrical certificate for the circuit does not prove that the seller met the smart-charge-point product rules. A domestic project can need evidence for both.

Inspection, testing and handover

The installer should assess enough of the existing installation to confirm that the new work can be connected safely. The scope depends on its condition and the proposed design. An Electrical Installation Condition Report is not automatically required before every charger, but defects affecting the new circuit cannot be ignored.

The completed work should leave a traceable record of:

• the supply and earthing arrangement used for the design
• maximum demand and any load-control settings
• the protective measures and device types
• circuit inspection and test results
• the electrical installation certificate
• Building Regulations notification where applicable
• DNO application or notification evidence where applicable
• charger commissioning, user controls and maintenance information

For a homeowner, these records are more useful than a general statement that the installation “follows the IET code”. They show what was actually designed, installed and tested at that property.

Related entries

• BS 7671 IET Wiring Regulations
• EVs Smart Charge Points Regulations
• RCD protection for EV chargers
• EV charger PEN fault detection
• Earth electrode and rod installation
• Dynamic load balancing CT clamps
• EV chargepoint commissioning
• Building Regulations Parts L and P
• Vehicle-to-home backup charging
• 7kW single-phase AC charging
• 22kW three-phase AC charging