EV Charger Installation: Electrical & Regulatory Guide

Why EV Charger Work Is Growing Fast

With the UK's 2035 ban on new petrol and diesel car sales, EV charger installations are one of the fastest-growing areas for domestic electricians. But this isn't just a case of running a cable and fitting a socket — there are specific regulations, earthing considerations, and documentation requirements that catch out even experienced sparks.

This guide covers the key electrical and regulatory requirements you need to get right on every EV charger install, whether it's a straightforward home wallbox or a more complex commercial setup.

Regulatory Framework: What Applies?

EV charger installations sit under several overlapping regulations:

• BS 7671 (18th Edition IET Wiring Regulations) — the core standard, particularly Section 722 which deals specifically with EV charging installations
• Building Regulations Part P — EV charger installation is notifiable work in England and Wales (it's a new circuit in a special location)
• IET Code of Practice for Electric Vehicle Charging Equipment Installation (4th Edition) — the practical companion guide to Section 722
• The Electric Vehicles (Smart Charge Points) Regulations 2021 — requires all home and workplace chargers to have smart functionality

BS 7671 Section 722: The Key Requirements

Supply Assessment

Before anything else, you need to carry out a thorough assessment of the existing supply. Most domestic Mode 3 chargers draw between 7.2 kW (32A single-phase) and 22 kW (32A three-phase). A typical UK home has a 60A or 80A single-phase supply, and a 7.2 kW charger on top of the existing load can push things tight.

You must verify:

• The incoming supply capacity (check the main fuse rating with the DNO if unsure)
• Maximum demand calculation to BS 7671 Appendix 1 — include the EV charger at its full rated load unless the charger has a built-in dynamic load management system
• The condition of the existing consumer unit — if it's an old rewireable fuse board, you'll likely need to upgrade it

Cable Sizing

Cable sizing must account for the sustained load nature of EV charging. Unlike a cooker or shower that cycles, an EV charger can draw its full rated current for hours continuously. This means you need to apply the appropriate correction factors carefully:

• Csa (ambient temperature) — if the cable runs through a loft space in summer, you could be looking at 35–40°C ambient
• Cg (grouping) — relevant if you're running alongside other loaded circuits
• Ci (thermal insulation) — if the cable passes through insulated areas, apply the appropriate derating
• Continuous load factor — BS 7671 requires cables to be rated for 100% of the charger's rated current as this is a continuous load (Regulation 722.531.1)

For a typical 32A single-phase install with a short run (up to about 20m), 6mm² twin and earth is often sufficient in favourable conditions. However, once you factor in longer runs, high ambient temperatures, or insulated voids, 10mm² is commonly needed. Always do the calculation — don't guess.

Voltage drop must not exceed 5% for the total circuit from the origin of the installation (Regulation 525). For a 32A circuit at 230V, that 5% equates to 11.5V. On a long garden run to a detached garage, you can eat through that allowance quickly.

Protection

Regulation 722.531.3 requires that the circuit supplying the EV charger has protection by an RCD with a rated residual operating current (IΔn) not exceeding 30mA. You have two main options:

1. Type A RCD + 6mA DC detection — a Type A RCD paired with a charger that has built-in DC fault protection (most Mode 3 chargers include this)
2. Type B RCD — provides both AC and DC fault protection but is significantly more expensive (often £150+ for the device alone)

Check the charger manufacturer's installation manual carefully. Most reputable units (Zappi, Andersen, Pod Point, Wallbox Pulsar) include internal DC leakage detection that satisfies 722.531.3.101, meaning you can use a standard Type A RCBO. If the charger doesn't include this, you'll need the Type B RCD.

The circuit also needs overcurrent protection — typically a 32A Type C MCB or RCBO for a 7.2 kW charger. Type C is preferred because the charger's switch-on inrush can nuisance-trip a Type B device.

Earthing Arrangements

Earthing is where EV installs get more complex, particularly on TT systems. Key considerations:

• TN-C-S (PME) supplies — Regulation 722.411.4.1 restricts the use of PME earthing for EV charging where the vehicle is connected outdoors. You must either confirm the charger has a protective device that disconnects the PME earth under fault conditions (PEN fault detection), or provide a separate earth electrode for the EV circuit. Many modern chargers include PEN fault detection — again, check the manual.
• TN-S supplies — no special earthing restrictions for EV charging. Standard earthing arrangements apply.
• TT systems — you'll need an adequate earth electrode. Verify the loop impedance allows the RCD to operate within the required disconnection time. An Rₐ of 1667Ω or less is needed for a 30mA RCD (50V/0.03A), but in practice you want a much lower value for reliable operation.

OZEV Grant Documentation

The Office for Zero Emission Vehicles (OZEV) has run various grant schemes including the EV Chargepoint Grant (which replaced the old EVHS). While grant availability and amounts change, the documentation principles remain consistent:

• Installer registration — you must be registered with OZEV as an approved installer to process grant claims. This typically requires membership of a Competent Person Scheme and completion of the relevant installer training.
• Pre-install photos — photographs of the proposed installation location before work begins
• Post-install photos — clear images of the completed installation, the charger serial number plate, and the consumer unit showing the new circuit
• Electrical Installation Certificate (EIC) — a full EIC (not a Minor Works Certificate) is required for every EV charger installation as it involves a new circuit
• Manufacturer commissioning certificate — many charger manufacturers require you to register the install on their platform and complete a commissioning checklist

Keep your paperwork thorough. OZEV audits are random but increasingly common, and a failed audit can mean repaying grants and losing your approved installer status.

Testing and Certification

Every EV charger installation requires a full Electrical Installation Certificate (BS 7671 Appendix 6, Model Form 1). The key tests you must record:

• Continuity of protective conductors (R1+R2)
• Insulation resistance (minimum 1MΩ at 500V DC)
• Earth fault loop impedance (Zs) — verify it meets the disconnection time requirements for the protective device
• RCD operation — both trip time (within 300ms at IΔn, within 40ms at 5×IΔn) and measured trip current
• Prospective fault current (PSCC) — ensure the protective device's breaking capacity is adequate
• Polarity check
• Functional testing of the charger itself — confirm it initiates and terminates a charge cycle correctly

If you've installed an earth electrode, you'll also need to measure and record the electrode resistance (Rₐ).

Common Mistakes to Avoid

1. Not checking the DNO supply capacity — a 32A charger on an already-loaded 60A supply will cause problems. Always do the maximum demand calculation.
2. Ignoring PME earthing restrictions — see the earthing section above. This is a safety-critical requirement.
3. Issuing a Minor Works Certificate instead of a full EIC — this is a new circuit, so a full EIC is mandatory.
4. Undersizing cables without proper calculation — don't assume 6mm² is always fine. Run the numbers every time.
5. Forgetting Part P notification — if you're in a Competent Person Scheme, self-certify and notify. If not, the work needs Building Control sign-off.

Further Resources

• OZEV Grant Schemes — GOV.UK
• IET Wiring Regulations (BS 7671)
• IET Code of Practice for EV Charging Installation

Published 2026-03-16. This article is for general guidance only and does not constitute legal or professional advice. Always refer to the relevant standards and consult qualified professionals for definitive requirements.