What Size Cable Do I Need for an EV Charger? UK Guide

Choosing an EV charger is only part of the installation.

The charger also needs a suitable electrical connection back to the property's electrical supply, and that means choosing a cable capable of safely carrying the required load.

So what size cable do you actually need?

There isn't one universal answer.

The correct specification depends on factors such as the charger's power, the length and route of the cable, how it is installed, voltage drop, ambient conditions and whether the cable needs additional protection such as armouring.

This guide explains what those factors mean in straightforward terms and why the final cable size should be confirmed as part of the installation assessment.

What Does “Cable Size” Mean for an EV Charger?

When people search for EV charger cable size, they can actually mean two different things.

There is the portable charging cable that connects an EV to an untethered chargepoint.

And there is the fixed electrical cable that runs from the property's electrical supply to the chargepoint.

This guide is about the second one.

The fixed cable is part of the electrical installation and is sized according to the load and conditions of the particular installation.

For portable Type 2 charging cables, see our guide to EV charging cables.

What Determines EV Charger Cable Size?

There isn't a single number that determines the cable size.

An installer needs to consider several things.

Charger power

A higher-powered charger can require a different electrical supply arrangement and cable specification.

A typical domestic 7kW chargepoint operates at around 32A on a single-phase supply, but the cable selection still depends on the complete installation.

Cable length

A longer run can increase voltage drop and may affect the required conductor size.

Installation method

The way the cable is installed affects how effectively it can dissipate heat.

Cable installed in free air can behave differently from cable surrounded by insulation, enclosed in certain routes or buried.

Cable grouping

Where cables are installed together, heat dissipation can be affected and correction factors may apply.

Ambient temperature

Higher temperatures can reduce a cable's ability to carry the same current without exceeding its temperature limits.

Voltage drop

The longer the cable run, the more important voltage drop becomes.

Property and electrical supply

The existing consumer unit, supply arrangement, protective devices and available capacity all matter.

This is why an installer should size the cable for the actual site, rather than simply selecting a cable based on charger power alone. (C-Lec Electrical)

What Size Cable for a 7kW EV Charger?

A 7kW home EV charger is commonly supplied at around 32A on a single-phase domestic supply.

You will often see 6mm² mentioned for typical domestic installations, while 10mm² may be appropriate where factors such as a longer run, installation method or voltage drop require additional capacity. Current UK guidance and competitor technical explainers commonly describe this 6mm²/10mm² range, but they also stress that the final size depends on the actual installation. (C-Lec Electrical)

So:

6mm² is not a universal answer.

And:

10mm² is not automatically better.

The correct cable is the one that meets the electrical requirements of that particular installation.

What About a 22kW EV Charger?

A 22kW AC charger is a very different proposition from a standard domestic 7kW setup.

It normally involves a three-phase supply and requires both the property and vehicle to support the higher charging power.

That means the cable specification cannot simply be chosen by taking a 7kW installation and multiplying the number.

The electrical supply, phases, protective devices, installation method and charger requirements all need to be considered.

Before choosing a 22kW charger, check whether your property and vehicle can actually make use of it.

For the charging-speed decision itself, see:

7.4kW vs 22kW EV Chargers: Which One Is Right for You?

When Is 10mm² Cable Used for an EV Charger?

You may come across 10mm² cable for EV chargers when looking at longer cable runs or installations with less favourable conditions.

For example, a longer route can increase voltage drop.

Other installation conditions can also reduce a cable's effective current-carrying capacity.

That does not mean every long installation automatically needs 10mm².

The installer needs to calculate the installation based on the actual cable route and conditions.

Current UK technical guides commonly identify 10mm² as a possible step-up from 6mm² for longer or more demanding domestic runs. (C-Lec Electrical)

What Is Armoured Cable for an EV Charger?

You may need to run the cable outside, underground or to a detached garage or outbuilding.

In situations like these, an armoured cable, commonly referred to as SWA, may be considered depending on the installation design.

The important point is that armouring is about protecting the cable and accommodating the installation route.

It is not simply a larger version of a normal EV charger cable.

The correct cable type depends on where the cable will run and what protection is required.

What Size Armoured Cable Do I Need for an EV Charger?

This is one of the questions where giving a blanket answer can be particularly misleading.

The answer depends on:

• Charger power

• Cable length

• Supply type

• Installation method

• Burial conditions

• Voltage drop

• Protective arrangements

• Other derating factors

Some domestic installations may use 10mm² SWA, while others may require something different.

Do not specify an armoured cable purely from the charger rating.

The installer should calculate the required specification for the actual route.

This distinction is particularly useful because searches for “what size armoured cable for EV charger” show clear informational intent.

Why Does Cable Length Matter?

Imagine two identical 7kW chargers.

One is installed close to the consumer unit.

The other is connected through a much longer cable route to a detached garage.

The charger power has not changed.

The installation conditions have.

As cable length increases, voltage drop becomes more significant, which can affect the required conductor size.

That is why the installer needs to measure the real cable route rather than making a decision from the distance visible between the charger and the house.

What Is Voltage Drop?

Voltage drop is the reduction in voltage that occurs as electrical current travels along a cable.

The longer the cable and the greater the current, the more important this becomes.

For an EV charger, the installer needs to check that the voltage at the chargepoint remains within the applicable limits.

This is one reason why a cable size that works for a short route may not be suitable for a much longer route.

Current installation guidance and technical sources identify voltage drop as one of the factors considered when selecting cable size. (C-Lec Electrical)

Does the Way the Cable Is Installed Matter?

Yes.

The same cable can have different thermal characteristics depending on how it is installed.

An installer may need to consider whether it is:

• Clipped directly to a surface

• Installed in conduit

• Routed through insulation

• Grouped with other cables

• Buried

• Installed in an area with higher ambient temperatures

These factors can change the cable's current-carrying capacity.

This is why simply copying someone else's cable specification from another property is not a reliable way to size an EV charger circuit.

Can an EV Charger Use the Existing Electrical Cable?

Sometimes an existing cable may be suitable.

Sometimes it may not be.

The important question is whether the existing circuit has the correct capacity, protection, route and installation characteristics for the proposed charger.

An installer should inspect and calculate this rather than assuming that an existing cable is suitable simply because it already powers something else.

Does a 7kW Charger Always Need 6mm²?

No.

This is one of the most important points in the entire article.

6mm² is commonly used in suitable domestic 7kW installations, but it is not a universal specification.

The required size may change depending on:

• Cable length

• Installation method

• Ambient conditions

• Cable grouping

• Voltage drop

• Protective devices

• Supply arrangement

Current UK technical guidance makes the same distinction: common cable sizes can be discussed, but the final selection has to account for the actual installation. (C-Lec Electrical)

10 Things to Check Before Your EV Charger Is Installed

1. Charger power

Know whether the charger is 3.6kW, around 7kW, 11kW or 22kW.

2. Single-phase or three-phase supply

The property's electrical supply affects the installation design.

3. Cable route

Know approximately where the cable will travel.

4. Total cable length

Longer runs can make voltage drop more significant and it depends on where the charger is installed.

5. Installation method

Surface-mounted, enclosed, buried and other routes can have different thermal considerations.

6. Ambient conditions

Hot spaces and other environmental factors can affect cable capacity.

7. Cable grouping

Other nearby cables can affect heat dissipation.

8. Armoured or unarmoured cable

The installation route may determine whether additional mechanical protection is needed.

9. Protective devices

The cable must form part of an appropriately protected electrical circuit.

10. Installer assessment

The final specification should be calculated for the actual property rather than copied from a generic chart.

Electrical Safety First advises using a qualified/competent installer for EV chargepoint installation, and its EV charging guidance stresses appropriate electrical assessment and protection. (C-Lec Electrical)

Can I Choose the EV Charger Cable Size Myself?

You can understand the factors involved, but the final electrical specification should not be treated as a DIY sizing exercise.

The cable needs to be selected as part of the complete electrical installation.

For homeowners, the useful questions to ask an installer are:

What cable size are you proposing?

How long is the cable run?

What installation method are you using?

Have you checked voltage drop?

Does any derating apply?

Why is this cable size appropriate for this installation?

That gives you a much better understanding of the work without attempting to design the electrical circuit yourself.

What Cable Size Is Used for a Home EV Charger?

For many standard UK domestic installations, you will commonly see 6mm² and 10mm² discussed.

But think of those as examples of commonly encountered sizes, not a universal prescription.

A short, straightforward installation may have very different requirements from a long run to a detached garage.

The correct answer is the one calculated against the actual conditions.

What About a Garage or Outbuilding?

A detached garage can make cable sizing more complicated because the cable may need to travel underground or outdoors for a significant distance.

The installer may need to consider:

• Longer cable runs

• Armouring

• Burial conditions

• Mechanical protection

• Voltage drop

• Different installation methods

• The electrical supply available at the property

This is exactly the type of installation where copying a standard “6mm² for 7kW” answer can become misleading.

Fixed Installation Cable vs EV Charging Cable

This distinction is worth remembering.

Fixed installation cable

Runs from the property's electrical supply to the chargepoint.

Cable sizing depends on electrical load and installation conditions.

Portable EV charging cable

Connects an untethered chargepoint to the vehicle.

This is where Type 2, cable length and portable cable ratings become relevant.

For Type 2 cables and choosing between 5m, 10m, 15m and 20m options, see:

EV Charging Cables Explained: Types, Lengths & How to Choose the Right Cable

That internal link is important because it clearly tells Google and the reader that the two articles serve different purposes.

Final Thoughts

There is no single cable size that is correct for every EV charger installation.

A standard 7kW home charger may commonly involve 6mm² or 10mm² cable, but the correct specification depends on the actual electrical installation.

Cable length, voltage drop, installation method, ambient conditions, grouping, protective arrangements and the property's electrical supply can all affect the result.

So rather than asking:

“What size cable does every EV charger need?”

The better question is:

“What cable size is appropriate for this charger, this property and this installation?”

That is the calculation your installer should be making.

FAQs

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

6mm² and 10mm² are commonly encountered in UK domestic installations, but the required size depends on the installation conditions, including cable length, route, voltage drop and installation method.

What size cable do I need for an EV charger in the UK?

There is no single universal size. The installer needs to consider charger power, current, cable length, installation method, voltage drop, ambient conditions and other electrical factors.

What size armoured cable do I need for an EV charger?

It depends on the charger, cable route, length, installation conditions and voltage-drop requirements. An installer should calculate the specification for the particular installation.

Does a 7kW EV charger need 6mm² cable?

Not always. 6mm² is commonly used in suitable installations, but longer or more demanding cable runs may require a different specification.

Does a 22kW EV charger need thicker cable?

A 22kW AC installation is usually a three-phase setup and has different electrical requirements. The cable size depends on the complete installation.

Why does cable length affect EV charger cable size?

Longer cable runs can increase voltage drop and may affect the required conductor size.

Can an EV charger cable be buried underground?

The installation needs to be designed for the underground route, including appropriate cable type, mechanical protection and other applicable requirements.

What is the difference between armoured and unarmoured EV charger cable?

Armoured cable incorporates additional mechanical protection and may be suitable for certain outdoor or underground routes. Whether it is needed depends on the installation.

Can I install an EV charger myself?

Electrical installation work should be carried out and certified by an appropriately qualified/competent installer. Electrical Safety First recommends professional installation for EV chargepoints. (C-Lec Electrical)