What Size Cable for a 7kW EV Charger?

For a typical 7kW home wallbox (which draws 32A on a single-phase 230V supply), installers commonly run 6mm² supply cable for ordinary run lengths, stepping up to 10mm² for longer runs or to keep voltage drop within limits. There is no single correct answer for your home: the exact size depends on the run length, the installation method, grouping, ambient temperature and the earthing arrangement, and it is chosen by a qualified electrician to BS 7671. If you landed here looking for the lead between your car and the charge point rather than the fixed wiring, see our EV charging cable length guide.

Which "cable" do you actually mean?

The word "cable" trips a lot of people up, because it means two completely different things in EV charging. Getting the right one saves you a wasted search.

• The supply or install cable: the fixed wiring an electrician runs from your consumer unit (fuse box) to the wallbox. It is measured in mm² (cross-sectional area), and it is chosen and fitted by a qualified installer. This is what "6mm or 10mm" refers to.
• The charging cable or lead: the Type 2 lead that plugs between the car and the charge point. It is measured in length (metres) and current (amps), not mm². This is the part we make.

We make EV charging cables (the lead), not the installation wiring. For the supply cable and the install itself, use a qualified EV installer. If what you actually need is a lead, you can shop charging cables by car or read the length guide. The rest of this article covers the supply wiring, in general terms.

Why is 6mm² common and 10mm² used for longer runs?

A 7kW charger pulls a steady 32A for hours at a time, which is a demanding, continuous load. The conductor has to carry that current safely without overheating, and it has to deliver enough voltage at the far end for the charger to work properly.

For many ordinary installations, where the wallbox sits a modest distance from the consumer unit, 6mm² is a common choice. On longer runs, the resistance of the cable adds up and the voltage at the charger can sag, so an installer will often go up a size to 10mm² to keep voltage drop within the limits set by BS 7671. This is a judgement call based on your specific route, not a fixed rule.

Treat the sizes below as typical starting points only. Your electrician confirms the final specification for your property.

The point of the table is not to pick your size for you. It is to show that run length is one of the biggest factors, alongside how and where the cable is run.

What else drives the size, besides length?

Length is only part of the picture. A competent installer weighs up several things together before settling on a cable.

• Installation method: clipped to a surface, run through insulation, in conduit or buried all behave differently for heat dissipation.
• Grouping: cables bundled with others cannot shed heat as easily, which can call for a larger size.
• Ambient temperature: warmer surroundings reduce how much current a cable can carry safely.
• Voltage drop: a longer run often means going up a size to keep the voltage at the charger within limits.
• Protection and earthing: the circuit protection and earthing arrangement all feed into the design.

Because these interact, the only reliable answer is the one your electrician calculates on site to BS 7671. Anyone quoting you a definitive size without seeing the route is guessing.

Indoors or outdoors: T&E or SWA?

The cable type depends on where it runs, not just how far.

Twin-and-earth (T&E)

T&E is suitable only for protected indoor runs, for example inside a garage or through the fabric of the building where it is not exposed to the weather or to mechanical damage.

Steel-wire armoured (SWA)

For outdoor, buried or exposed runs, installers use SWA cable. The steel armour gives mechanical protection for a route that crosses a garden, a driveway or an external wall. Where a cable is buried, it must be at an adequate depth with warning tape and mechanical protection in line with the regulations. Your installer sets the depth and method for your ground conditions.

Is a 7kW install notifiable work?

Yes. In England and Wales, installing or altering an EV charge point circuit is notifiable work under Part P of the Building Regulations. It must be carried out by a registered competent person, for example a firm registered with NICEIC, NAPIT or Stroma, or otherwise notified to building control. Scotland and Northern Ireland have their own equivalent rules.

DIY is only legal if the work fully complies and is properly notified and inspected, and we strongly discourage it for EV circuits. These are high-current, long-duration loads, and the consequences of getting the design wrong are serious. Use a qualified EV installer. For a sense of the full process, see our guide on what to expect from a home charger installation.

Your installer will also notify the Distribution Network Operator (DNO) for the charge point. Some supplies or higher-output installs need prior approval before work begins, which can add a little time to the schedule.

What if my supply cannot take another 32A?

Not every home has spare headroom on the main fuse for a continuous 32A load on top of cookers, showers and everything else. When the supply is tight, the usual fix is not an expensive supply upgrade.

Instead, the installer can fit a load manager with a CT clamp around the incoming supply. This monitors how much the house is drawing and automatically backs the charger off when demand is high, then lets it ramp up again when there is spare capacity. It is a common, cost-effective way to add a 7kW charger without overloading the supply, and your installer will advise whether your property needs one.

What about 22kW? Do I need a bigger cable?

At home, probably not, because most UK homes are single-phase and cannot run 22kW without a three-phase supply. A 22kW charger needs roughly 32A on each of three phases, which calls for a supply upgrade through the DNO. That is uncommon, expensive and not worth it for most households, since the car's onboard charger often limits home charging anyway.

Where three-phase is available, a 22kW install uses a multi-core cable, such as a 5-core SWA, sized to the installer's design. If you are weighing up speed, read 7kW vs 22kW, do I need a 22kW cable, and single-phase vs three-phase charging. For most drivers, a 7kW single-phase install is the sensible choice.

Sizing the charging lead (the other kind of "size")

If you came here meaning the lead, not the wiring, the sizing logic is completely different. A charging lead is sized by length and by your car's inlet, not by mm².

• Length: 5m suits most driveways, with 7.5m or 10m for awkward parking or a charge point that is a fair walk from the charging port.
• Connector and current: match the lead to your car's inlet (Type 1 or Type 2) and its current rating.

A bigger or longer lead never makes the car charge faster than its onboard limit, so there is no benefit in overspecifying. See the length guide to choose, then shop charging cables by car. You can also browse all our guides for related reading.

Are there grants to help with the cost?

Support does exist for some situations, such as flats, renters and landlords, though eligibility and amounts change. We will not quote figures here, because they move. Check gov.uk for the current EV chargepoint grants before you book, and ask your installer whether your situation qualifies.

Frequently asked questions

What size cable do I need for a 7kW EV charger?

For a 7kW (32A single-phase) charger, 6mm² supply cable is common for ordinary run lengths and 10mm² is often used for longer runs or to keep voltage drop within limits. The exact size depends on the run length, installation method, grouping, ambient temperature and earthing, and your electrician confirms it to BS 7671.

Is 6mm cable enough for a 7kW charger?

It often is for shorter runs, but it is not guaranteed for your property. Voltage drop, installation method and conditions all matter, so a qualified electrician checks the calculation and may step up to 10mm² on a longer run.

Do I need 10mm cable for an EV charger?

Not always. 10mm² is commonly used where the run is long enough that 6mm² would exceed the voltage drop limits, but the decision belongs to your installer based on your specific route and conditions.

Can I install the charger cable myself?

Installing or altering an EV charge point circuit is notifiable work in England and Wales under Part P, so it should be done by a registered competent person or notified to building control. DIY is only legal if it fully complies and is notified and inspected, and we strongly discourage it for EV circuits.

Do I need SWA cable for an outdoor run?

For outdoor, buried or exposed routes, installers use steel-wire armoured (SWA) cable for mechanical protection, while twin-and-earth is only for protected indoor runs. Buried cable must be at an adequate depth with warning tape and protection to the regulations, which your installer sets.

Is the charging cable the same as the supply cable?

No. The supply cable is the fixed mm² wiring an electrician runs to the wallbox. The charging cable is the Type 2 lead between the car and the charge point, sized by length and current. We make the charging lead, not the installation wiring.