The short answer
An EV consumer unit (or EV charger board) is a small dedicated consumer unit installed to supply an electric vehicle charging point. Rather than taking the EV charger circuit directly from the main house board, a separate sub-board is used — often because the main board is full, because the charger is in a detached garage requiring its own distribution point, or because the installer wants a dedicated isolation point for the EV supply. The board contains a main isolator, appropriate RCD protection (at minimum Type A, since EV chargers produce pulsating DC fault currents that Type AC cannot detect), and an MCB or RCBO sized for the charger's current. For bidirectional (V2G) chargers, the RCD protection required is Type B, because the charger can inject smooth DC fault current back through the supply cable. An EV consumer unit installation is notifiable Part P work.
Adding an EV charger to a UK home almost always means electrical work at the consumer unit — either adding a circuit to the existing board, or installing a dedicated sub-board. Understanding when and why a separate EV consumer unit is used helps homeowners ask the right questions when getting quotes.
EV consumer unit facts
- PurposeDedicated supply for EV charging point(s)
- Min RCD typeType A (for standard Mode 3 chargers)
- V2G charger RCDType B required
- Typical charger rating7.4 kW = 32 A single-phase
- Part P statusNotifiable — registered electrician required
- SPDRequired under BS 7671 Amd 2 for new boards
When a dedicated EV consumer unit is used
Many EV charger installations do not need a separate board — the charger circuit is simply added to a spare way in the main consumer unit. A dedicated EV consumer unit is typically used when:
- The main consumer unit is full (no spare ways), making it impractical to add a circuit without replacing the whole board.
- The charger is located in a detached garage or outbuilding that already has (or needs) its own sub-board for other circuits.
- The installer wants a dedicated isolation point near the charger for safety or maintenance purposes.
- A load management device is being used (a device that monitors the main supply and limits the charger current to avoid exceeding the incoming fuse rating), and a separate board provides a cleaner installation.
In an attached garage or when the main board has a spare way and the right RCD type, the charger circuit is often simply added to the existing installation without a separate board.
RCD type requirements for EV chargers
The choice of RCD type is the most technically significant aspect of EV charger protection. A standard Mode 3 EV charger (the type that connects to a dedicated wall-box) contains an internal rectifier. If an earth fault develops inside the charger, the fault current will include a pulsating DC component. A Type AC RCD may not detect this reliably, or may be desensitised by it. BS 7671 18th Edition therefore requires a minimum of Type A RCD protection for circuits supplying EV chargers.
Some EV charger manufacturers and their installation instructions specify even stricter protection. Certain charger designs integrate Type A protection internally; where the charger provides its own RCD protection to a verified standard, the external RCD requirement may be satisfied by the charger itself. Always check the charger manufacturer's installation manual and confirm with the installing electrician.
For bidirectional (V2G) chargers — which can export power from the vehicle back to the home or grid — the fault current profile changes. During export the charger can introduce smooth DC fault currents into the supply conductors. The product standards for V2G chargers specify Type B RCD protection at the point of supply, because smooth DC is outside the detection capability of Types A and F.
What a typical EV consumer unit contains
A dedicated EV sub-board for a single charger is a small unit — typically a 4-way or 6-way board with the following contents:
- Main isolator / double-pole switch: provides isolation of the entire sub-board without having to go back to the house. Typically rated at 40 A or 63 A.
- RCBO or MCB + RCD: protecting the charger circuit. For a standard 7.4 kW (32 A) charger, a 32 A device is typical. The RCD element must be Type A (or Type B for V2G).
- Surge protection device (SPD): required under BS 7671 Amendment 2 for new boards. Protects the charger's sensitive electronics against voltage spikes.
- Spare ways for future circuits if the board is being installed in a location where further circuits may be needed.
| Component | Typical specification | Notes |
|---|---|---|
| Main isolator | 40 A or 63 A double-pole | Sized for submain cable |
| Charger RCBO | 32 A, Type A RCD element | For 7.4 kW Mode 3 charger |
| V2G charger RCBO | 32 A, Type B RCD element | Required for bidirectional chargers |
| SPD | Type 2, 30 kA | Required on new boards under BS 7671 Amd 2 |
| Board size | 4-way or 6-way | Allows spare capacity for future circuits |
Typical components in a dedicated EV charger consumer unit. Actual specification depends on the charger and installation design. Source: BS 7671:2018+A2:2022.
Frequently asked questions
Do I need a separate consumer unit for my EV charger?
Not necessarily. If your existing consumer unit has a spare way and the appropriate RCD type, the charger circuit can often be added to the existing board. A separate EV consumer unit is used when the main board is full, when the charger is in a detached outbuilding that needs its own sub-board, or for practical installation reasons. Your electrician will advise based on your specific installation.
Can I use my existing consumer unit for an EV charger?
Yes, if it has a spare way and the RCD covering the new circuit is Type A (not Type AC). If the existing RCDs are Type AC, the electrician may recommend upgrading them or adding an RCBO with a Type A RCD element for the charger circuit. The overall installation design matters — always use a registered electrician for EV charger installation.
Is EV charger installation Part P notifiable work?
Yes. Installing a new circuit for an EV charger is notifiable work under Part P of the Building Regulations in England and Wales. It must be carried out by a registered competent person who self-certifies, or notified to building control. You should receive an Electrical Installation Certificate (EIC) and a Building Regulations compliance certificate on completion.
Sources & further reading
- IET — BS 7671:2018+A2:2022 (18th Edition Wiring Regulations)
- OZEV (Office for Zero Emission Vehicles) — EV charge point guidance
- NICEIC — EV charger installation guidance
Figures on this page are typical UK ranges drawn from published sources and depend on your specific property and installation. They are guidance, not a quotation.