The answer depends on which type of charging you’re doing. If your granny charger cable (Mode 2, the one with the little black safety box on it) won’t reach the socket, the answer is: do not extend it with a domestic extension lead. That approach bypasses the safety device and is not permitted. If your wallbox cable (Mode 3) won’t reach the car, there is a proper solution: a purpose-built Type 2 extension cable, rated for 32A and fitted with the correct connectors at both ends. These are two different problems with two different answers.
Mode 2 vs Mode 3: the extension question is different for each
You cannot use a standard domestic 13A extension lead to charge an electric car, for either Mode 2 (granny charger) or Mode 3 (wallbox) charging. For Mode 3 wallbox charging, however, a purpose-built Type 2 extension cable (male Type 2 one end, female Type 2 the other, rated for 32A) is the correct solution.
The two scenarios have different answers because the safety intelligence sits in a different place in each case.
Mode 2 is a granny charger, defined by IEC 62752 as a charging cable with an In-Cable Control and Protection Device (IC-CPD) built in. That’s the black box partway along the cable between the 13A plug and the Type 2 connector. The IC-CPD monitors earth continuity, limits current, and communicates with the vehicle. Plug a domestic extension lead between the wall socket and the IC-CPD and you’ve added uncontrolled resistance and potentially defeated the earth-continuity monitoring. IEC 62752 is explicit: an extension cable cord set shall not be added to a Mode 2 charging cable.
Mode 3 is a different architecture. Here, the safety intelligence lives in the fixed wallbox (the EVSE), not the cable. The cable is a conductor between wallbox socket and car. That changes the equation: a purpose-built Type 2 extension cable extends the conductor without bypassing any protection device.
- Two columns. Mode 2 (Granny/IC-CPD): 13A plug → IC-CPD box → Type 2 car connector | NEVER add domestic extension lead: bypasses IC-CPD protection (IEC 62752). Mode 3 (Wallbox EVSE): Wallbox socket → Type 2 cable → car | CAN use proper Type 2 extension cable (male Type 2 → female Type 2, 32A rated, correct connectors)
Why you must never use a domestic 13A extension lead with an EV charger
A domestic 13A extension lead bypasses the IC-CPD safety device built into a Mode 2 granny cable, the device specified by IEC 62752 that monitors earth continuity, current limits, and communication with the vehicle. It is also not rated for the sustained 32A current EV charging draws, and sits outside the fixed-wiring protections of BS 7671 Section 722.
Three distinct failure modes apply:
1. It bypasses the IC-CPD (Mode 2) The IC-CPD checks earth continuity at the socket before letting current flow. Put an extension lead between the socket and the IC-CPD and the device now reads the earth at the extension plug, not at the wall. A corroded or faulted socket earth goes undetected. IEC 62752 prohibits this for this exact reason.
2. Domestic extension leads are not rated for sustained 32A A standard 13A extension lead handles short-duration peaks. EV charging at 7kW draws a sustained 32A for hours. The conductor cross-section is undersized, the insulation is not rated for the heat generated over a full overnight charge, and domestic sockets are not designed for continuous load cycling. Overheating follows, often behind furniture or inside cable trunking where it goes unnoticed.
3. Extension leads sit outside the BS 7671 fixed-wiring protection scope BS 7671:2018+A2:2022 (IET Wiring Regulations), Section 722 governs EV circuits and mandates dedicated overcurrent protection and RCD protection for EV charging points. A domestic extension lead is not a fixed-wiring installation. It has no dedicated breaker sized for EV current and no RCD protecting the lead itself. The IET Code of Practice for EV Charging Equipment Installation, 5th edition (2023) is clear: extension cords are not a compliant installation method for EV charging.
The proper solution for Mode 3: what a Type 2 extension cable actually is
A proper Type 2 extension cable is the correct Mode 3 approach.
When your wallbox cable won’t reach the car (a common scenario when the wallbox is mounted inside a garage and the car parks just outside), the answer is a purpose-built Type 2 extension cable. Not a domestic lead. Not a creative bodge.
A Type 2 extension cable has a male Type 2 connector at one end (plugs into the wallbox socket) and a female Type 2 socket at the other (your car’s cable plugs in here). It is rated for sustained EV charging current: 32A for 7kW single-phase, or appropriately rated for 22kW three-phase use.
What to look for:
- Current rating: 32A minimum for 7kW wallbox use
- Conductor cross-section: 6mm² copper for runs over 10m at 32A
- IP rating: IP55 or better for outdoor connector exposure
- Connectors: certified IEC 62196-2 Type 2 at both ends
If your total cable run will exceed 10m, read our guide to long-run EV charging cables. Conductor sizing becomes critical at longer distances.
Voltage drop: why cable run length matters
The IET Code of Practice caps voltage drop at 5%; at 32A over a long run this matters.
Every metre of copper conductor adds resistance, and resistance loses voltage. The longer the total run from wallbox socket to charge port, including any extension, the more voltage arrives depleted at the car.
The IET Code of Practice for EV Charging Equipment Installation, 5th edition (2023) sets the limit: voltage drop must not exceed 5% of supply voltage. At 230V and 32A, that is an 11.5V ceiling. With properly sized 6mm² copper cable, voltage drop stays within the IET 5% limit across every length we sell, reaching that ceiling only at a full 50m run:
| Total cable run | Approx. voltage drop (6mm², 32A) | Within IET CoP 5% limit? |
|---|---|---|
| 5m | ~0.5% | Yes |
| 10m | ~1.0% | Yes |
| 15m | ~1.5% | Yes |
| 20m | ~2.0% | Yes |
| 30m | ~3.0% | Yes |
| 40m | ~4.0% | Yes |
| 50m | ~5.0% | At the limit |
Calculated at 32A single-phase, 6mm² copper, resistivity 0.0168 Ω·mm²/m.
The risk comes with undersized cable: 2.5mm² at 32A over 20m will exceed the 5% ceiling and can cause the car’s onboard charger to reduce its charging rate or fault out.
- Total run 5m ≈ 0.5% drop | 10m ≈ 1.0% | 15m ≈ 1.5% | 20m ≈ 2.0% | 30m ≈ 3.0% | 40m ≈ 4.0% | 50m ≈ 5.0% (at 6mm² copper, 32A), with IET CoP limit = 5% shown as horizontal reference line
Our EV cable length guide covers how to calculate your total run from wallbox height to charge port position.
Quick-reference: which solution for which scenario
| Scenario | What you need | What NOT to do | Why |
|---|---|---|---|
| Granny cable (Mode 2) too short | Buy a longer granny cable | Use a domestic 13A extension lead | Bypasses IC-CPD protection: unsafe |
| Wallbox cable too short (Mode 3) | Proper Type 2 extension cable (32A rated) | Standard domestic extension reel | Not rated for sustained 32A; no RCD |
| Wallbox too far from parking spot | Longer Type 2 cable or Type 2 extension | Daisy-chain anything | Voltage drop + safety |
Mode 2 (granny): there is no extension approach that is safe. The IC-CPD is the protection system for the entire session and cannot be circumvented. Buy a longer granny cable.
Mode 3 (wallbox): a proper Type 2 extension cable is a legitimate tool. If you’ll always need the extra reach, a longer charging cable from the outset avoids storing an extension separately.
Frequently asked questions
Can I use a domestic extension lead to charge my EV?
No. A standard 13A domestic extension lead must never be used with an EV charger. For Mode 2 (granny charger), it bypasses the IC-CPD safety device. For Mode 3 (wallbox), it is not rated for sustained 32A current and has no RCD protection. Use a proper Type 2 extension cable for Mode 3 wallbox use instead.
What is a Type 2 extension cable for an EV charger?
A Type 2 extension cable is a purpose-built cable with a male Type 2 connector at one end and a female Type 2 socket at the other. It plugs into your wallbox’s Type 2 socket and extends the reach to your car’s cable. It must be rated for 32A (7kW) or appropriately for 22kW three-phase use.
Can I extend a granny charger cable?
No. A Mode 2 granny charger cable contains an IC-CPD safety device (specified by IEC 62752) that monitors earth continuity, current, and communication with the car. Adding any extension lead bypasses this protection. The only safe solution is to buy a longer granny cable.
How much voltage drop is acceptable in an EV charging cable run?
The IET Code of Practice for EV Charging Equipment Installation, 5th edition (2023) specifies that voltage drop must not exceed 5% of the supply voltage. At 32A on a 230V supply, that means no more than 11.5V drop across the total cable run. With 6mm² copper cable this limit is met comfortably up to around 50m total run.
What should I look for in a Type 2 EV extension cable?
Look for: 32A current rating minimum; conductor cross-section of at least 6mm² for runs over 10m; IP55 or better weather rating; certified IEC 62196-2 Type 2 connectors at both ends. Avoid any extension using non-standard connectors or cable not rated for sustained EV charging current.
Is it better to use an extension cable or buy a longer EV cable?
For permanent home use, buying a longer cable from the outset is cleaner, with fewer connectors in the chain and nothing extra to store. A Type 2 extension cable suits temporary reach problems or situations where you charge in two locations requiring different cable lengths.
Find yours in Type 2 EV charging cables.