EV Charger Installation: Circuit Requirements, DNO Notification & OZEV Grant

Summary

The UK has millions of EVs on the road and home charging is by far the most cost-effective way for drivers to charge. As a result, EV charger installation has become one of the most in-demand services for domestic electricians. Getting the installation right matters: a 7kW charger draws 32A continuously — significantly more than most domestic circuits — and the combination of outdoor location, long cable runs, and high continuous load demands careful design.

The regulatory landscape has evolved quickly. OZEV (the Office for Zero Emission Vehicles) administers grant funding under the Electric Vehicle Homecharge Scheme (EVHS). To qualify, chargers must be installed by an OZEV-authorised installer, must be smart chargers (capable of off-peak load shifting), and must be fixed to the building structure. This scheme has replaced the earlier OLEV EVHS scheme and grant amounts and eligibility criteria have changed — always check the current OZEV guidance.

DNO (Distribution Network Operator) notification requirements are a source of confusion. Most chargers are 7kW (32A, single phase) and these require notification to the DNO before installation, though in practice most DNOs have a fast-track process that allows installation to proceed immediately provided certain conditions are met.

Key Facts

• Standard home charger — 7kW (32A, single phase); charges a typical 60kWh battery from empty in 8-9 hours
• Fast charger — 22kW (32A, three phase); requires three-phase supply; most homes don't have this
• DNO notification threshold — Generators/EV chargers above 3.68kW (16A) require DNO notification under G100
• OZEV grant amount — Up to £350 for eligible homeowners and renters (check current OZEV guidance as amounts change)
• Grant eligibility — Requires OZEV-authorised installer, smart charger, off-street parking, new or nearly new EV
• RCD type — Type A or Type F RCD required (not Type AC); most charger manufacturers specify one in their installation manual
• MCB rating — 32A Type B MCB for a 7kW charger
• Cable sizing — Minimum 6mm² for a 32A circuit; check volt drop if run exceeds 20m
• Earthing — PME (TN-C-S) earthing requires special consideration; many charger manufacturers require a PEN fault detection device if using PME earth
• PME prohibition — Some EV charger installations on PME supplies require an earth electrode; check manufacturer requirements
• Smart charging — OZEV-funded chargers must support smart (off-peak) charging; must be compatible with randomised delay scheduling
• Tethered vs untethered — Tethered (cable attached) or untethered (socket only) — untethered requires a Type 2 socket
• Commissioning — Must be tested to BS 7671 and a certificate issued; smart charger must be registered with the manufacturer
• Part P — New circuit from consumer unit is notifiable work; must be done by a competent person

Quick Reference Table

Detailed Guidance

DNO Notification (G100)

Engineering Recommendation G100 (previously G83) governs connection of low-voltage generation equipment and EV chargers to the distribution network. For EV chargers:

• Single phase chargers up to 3.68kW (16A) — no DNO notification required
• Single phase chargers 3.68kW to 7.36kW (16A to 32A) — DNO notification required; most DNOs accept a "standard connection" notification
• Chargers above 7.36kW — DNO technical assessment may be required

In practice, the major DNOs (National Grid, Northern Powergrid, UK Power Networks, etc.) have simplified forms for 7kW residential EV charger installations. Submit the notification and the DNO will either confirm acceptance or respond with additional requirements within a defined period (typically 28 days, though most respond faster).

The notification process exists because a street with 10 homes all charging at 7kW simultaneously would exceed the capacity of many local distribution transformers. Load management and smart charging requirements are partly a response to this.

PME Earthing and PEN Fault Detection

This is the most technically complex part of UK EV charger installation:

Most UK domestic supplies use PME (Protective Multiple Earthing, also called TN-C-S) earthing, where the neutral and earth are combined in the distribution network. Under fault conditions, a broken neutral can result in the vehicle's chassis becoming live.

BS 7671:2018+A2:2022 (Regulation 722.411.4) requires one of the following for EV charger installations on PME supplies:

1. PEN fault detection device — Detects a broken neutral and disconnects the charger; most modern charger units include this or it's available as an accessory
2. Earth electrode — Install a dedicated earth rod (minimum 1.2m long copper-clad steel) at the charger location; connect the charger's earth to this electrode rather than the PME earth

In practice, most OZEV-approved chargers include a PEN fault detection device as standard. Check the installation manual — it will specify the requirement for your supply type.

Circuit Design

A 7kW EV charger is a continuous load — it may run for 8+ hours at 32A. Design accordingly:

• Cable selection — 6mm² is fine for runs up to about 20m; use 10mm² for longer runs to keep volt drop within 5%
• Volt drop calculation — At 32A over 20m in 6mm² cable, volt drop is approximately 5.9V (2.5%), acceptable; over 30m it rises to 3.8%, still acceptable but check both ways
• Consumer unit space — You'll need a spare way for a 32A RCBO (MCB + RCD combined); if the CU is full, a new CU or sub-distribution board may be needed
• Cable route — Underground runs should use SWA cable at 750mm depth under driveway or 500mm in garden

OZEV Grant (EVHS)

The Electric Vehicle Homecharge Scheme provides up to £350 (50% of installation cost) for eligible installations. Key conditions as of early 2026:

• Must be an OZEV-authorised installer
• The charger must be on the OZEV-approved product list
• Must be a smart charger with scheduling capability
• Homeowners must own or lease a qualifying EV
• Property must have off-street parking
• Grant cannot be combined with other government grants for the same installation

Renters and flat owners in blocks with dedicated parking may also qualify — check the OZEV website for current eligibility criteria as these have changed several times.

To become an OZEV-authorised installer, you need to be registered with an OZEV-approved competent person scheme (NAPIT, NICEIC, or similar).

Common Installation Mistakes

• Using Type AC RCD — Won't detect DC fault currents that some EV chargers can produce; always use Type A or Type F as specified in the charger manual
• Ignoring PME requirements — Not installing PEN fault detection or an earth electrode is both a safety hazard and non-compliant with BS 7671
• Undersizing cable — 4mm² is not adequate for a 32A continuous load; use 6mm² minimum
• Not registering the charger — Many OZEV grants and warranties require the charger to be registered with the manufacturer via an app or web portal at commissioning

Frequently Asked Questions

Does every EV charger installation need building control notification?

Yes, in practice. Installing a new dedicated circuit from the consumer unit is notifiable work under Part P of the Building Regulations. If you're an OZEV-authorised installer registered with NAPIT, NICEIC, or another approved competent person scheme, you can self-certify without separate building control notification. Non-registered electricians must notify building control before starting work.

Can I install a 7kW charger on a 100A supply?

Yes, in most cases. A standard domestic supply is 100A (23kW). A 7kW charger plus typical house loads (cooking, heating, lighting) typically stays within this limit. If you have electric heating or other large loads, check that the maximum demand doesn't exceed the supply capacity. A 32A charger draws 7.36kW — add this to peak household consumption and verify it's within the supply fuse rating.

What's the difference between a tethered and untethered charger?

A tethered charger has the cable permanently attached — the driver simply plugs into the car. An untethered charger has a socket (Type 2 socket) and the driver uses their own cable. Tethered is more convenient for most homeowners (one fewer thing to forget). Untethered is better if multiple vehicles with different connectors will be charged, or if you want flexibility for future vehicles. Most modern EVs use Type 2 (Mennekes) connectors.

What happens if my consumer unit is full?

You have several options: replace the existing consumer unit with a larger one (notifiable work), install a split-load CU, or fit a separate two-way consumer unit next to the existing one, fed from a suitable spare way or from the meter tails via an isolator. The EV charger does not necessarily need to be in the main CU — a small sub-board adjacent to the charging location is acceptable.

Regulations & Standards

• BS 7671:2018+A2:2022 — IET Wiring Regulations; Section 722 covers electric vehicle charging installations specifically

• Engineering Recommendation G100 — DNO connection requirements for EV chargers and low-voltage generation

• Part P of the Building Regulations — New circuits are notifiable work; requires competent person or building control

• OZEV Electric Vehicle Homecharge Scheme — Government grant scheme for home EV charger installations

• PAS 1899:2022 — British Standard for EV charging equipment; covers smart charging requirements

• OZEV Electric Vehicle Homecharge Scheme — Official grant guidance

• IET Code of Practice for Electric Vehicle Charging Equipment Installation — Detailed installation guidance

• Energy Networks Association G100 — DNO connection requirements

• outdoor electrics — IP ratings and RCD requirements for outdoor installations

• consumer units — Consumer unit standards and circuit protection

• part p notifications — Part P notification requirements