Not all EV charging cables are built the same, and the difference is hidden inside the jacket. The copper conductor quality, cross-section size, and sheath material determine whether your cable charges safely at 32A for a decade or quietly degrades from its first winter. In this guide we explain oxygen-free copper (OFC), what cable gauge you actually need, why cheap CCA cables are a genuine safety risk, and how to tell the difference before you plug in.
What does OFC mean in an EV cable?
OFC stands for oxygen-free copper: a high-purity copper conductor with a resistivity of roughly 0.0168 Ω·mm²/m. The “oxygen-free” designation matters because it reduces internal grain boundaries that cause work-hardening over time. In an EV cable that is plugged and unplugged daily, OFC conductors flex millions of times without developing micro-cracks, keeping resistance stable and heat generation low throughout the cable’s life.
This matters more than most buyers realise. An EV cable running at 32A overnight for seven or eight hours is a continuous high-current session, not a casual use case. The conductor material underpins everything: how much heat is generated, how reliably the cable performs in year five versus year one, and whether resistance stays stable or climbs silently over time.
If you are still choosing between cable types and amperages, our guide to choosing the right EV cable covers the full picture before you get into conductor specs.
How OFC compares to CCA (copper-clad aluminium)
CCA (copper-clad aluminium) has a resistivity approximately 55% higher than pure copper: around 0.026 Ω·mm²/m versus 0.0168 for OFC. At 32A continuous overnight charging, that extra resistance means measurably more heat in the cable. CCA conductors also work-harden at repeated flex points, developing micro-cracks over months of daily use. The result is a cable whose resistance quietly climbs over time, a hidden safety regression you cannot see from the outside.
- Rows:
- Property: Resistivity | OFC: ~0.0168 Ω·mm²/m | CCA: ~0.026 Ω·mm²/m | Winner: OFC
- Property: Heat at 32A continuous | OFC: Low | CCA: ~55% higher resistance → measurably more heat | Winner: OFC
- Property: Flex durability | OFC: Millions of bend cycles; does not work-harden easily | CCA: Work-hardens; micro-cracks develop at flex points | Winner: OFC
- Property: Cold weather behaviour | OFC: Unaffected at conductor level | CCA: Micro-crack risk increases in cold | Winner: OFC
- Property: Weight | OFC: ~0.30 kg/m (6mm² 5-core) | CCA: Noticeably lighter, a red flag | Winner: OFC (heavier = genuine copper)
- Property: Price | OFC: Higher | CCA: Lower | Winner: CCA (short-term only)
- Property: Long-term safety | OFC: Stable resistance over years | CCA: Resistance increases over time | Winner: OFC
CCA cables are not always sold dishonestly, but they are frequently sold without adequate disclosure. You will find them marketed as “copper EV cables” on major marketplaces, because the copper cladding makes that claim technically defensible in the narrowest sense. The practical performance, however, is not comparable.
The weight test: how to spot a CCA cable at home
Copper is approximately 30% denser than aluminium, which means a CCA cable claiming to be 6mm² will be noticeably lighter than a genuine OFC cable of the same length. Weight does not lie. In our experience at EV Cable Hub, a 5-metre 6mm² OFC cable for 32A single-phase use weighs around 1.5 kg. If a cable of the same spec and length feels suspiciously light, the conductor material should be questioned before purchase.
EV cable gauge explained: which mm² do you need?
The cross-section of the copper conductor, measured in square millimetres (mm²), determines the maximum safe continuous current the cable can carry. Get this wrong and the cable overheats. The table below shows the standard cross-sections used in UK EV charging cables:
| Cross-section | Max safe continuous current | Power (single-phase) | Power (three-phase) | Notes |
|---|---|---|---|---|
| 2.5mm² | 16A | 3.7kW | N/A | Adequate for 16A granny charger; NOT for 32A |
| 4mm² | 20-25A | Up to ~5.5kW | : | Mid-range; not the standard for 32A |
| 6mm² | 32A | 7.4kW | 22kW | UK standard for 32A home charging |
| 10mm² | 32A+ (long runs) | 7.4kW (less voltage drop) | 22kW | Long cable runs, commercial installs |
For 32A single-phase charging, the standard for a 7.4kW home wallbox, you need a minimum 6mm² conductor cross-section. A 2.5mm² cable is only rated for continuous currents up to 16A and must never be used at 32A; doing so risks overheating the conductors. BS 7671:2018+A2:2022 (IET Wiring Regulations), Section 722 specifies cable sizing for EV charging circuits and underpins this requirement.
Our EV cable amps explained guide goes deeper on how current ratings translate to real-world charging speeds if you want more context before choosing. For a direct comparison of 16A versus 32A cables for home use, see our 16A vs 32A charging cable guide.
2.5mm² vs 6mm²: the 32A safety line
The jump from 2.5mm² to 6mm² is a safety threshold, not a marginal upgrade. A 2.5mm² cable run at 32A will carry roughly double its rated current capacity. The conductor resistance generates heat proportional to current squared (P = I²R), meaning the heat load at 32A in a 2.5mm² conductor is around four times greater than at 16A. This is why undersized cables overheat at connection points and why the difference between 16A and 32A cables is not simply a matter of charging speed.
When to use 10mm² (long runs and three-phase)
For standard home charging runs up to about 10m, 6mm² OFC is the correct specification. Once runs exceed 15m, resistive voltage drop becomes more significant, and this is where 10mm² conductors earn their keep. The larger cross-section reduces resistance per metre, keeping voltage drop within acceptable limits at 32A. For three-phase 22kW commercial installations, 10mm² is frequently specified for any run over a short distance. See our EV cable length guide and the dedicated guide to longer EV charging cables (15m: 25m) for detailed guidance on cable length selection.
What’s inside an EV cable? Anatomy of a Type 2 cable
Understanding what is physically inside your cable makes the spec choices above concrete. A Type 2 EV charging cable is more complex than it looks: there is more than just copper wire inside the jacket.
- Layer 1 (outermost): TPU outer sheath, dark grey, label TPU Outer Sheath (IP55, -40°C rated)
- Layer 2: Strain relief zone, lighter grey band, label Strain Relief
- Layer 3: Individual conductor insulation, coloured rings per conductor
- Layer 4: Five OFC copper conductors:
- Brown ring: L: Live (Brown)
- Blue ring: N: Neutral (Blue)
- Green/Yellow ring: PE: Protective Earth (Green/Yellow)
- Thin orange ring: CP: Control Pilot
- Thin white ring: PP: Proximity Pilot
- Centre label: OFC Copper Conductors (6mm² for 32A)
From the outside in, the structure is:
- TPU outer sheath: the weatherproofing layer, responsible for UV resistance, abrasion protection, and cold-weather flexibility
- Strain relief: at each plug end, this prevents flexing forces from being transmitted to the conductor terminations
- Individual conductor insulation: each copper conductor is wrapped in colour-coded insulation
- Copper OFC conductors: the current-carrying cores
- Ground / PE conductor: green and yellow, always present, always connected
Conductor count: single-phase vs three-phase
A single-phase EV cable (for home wallboxes and most UK public chargers) uses three power conductors: Live (L), Neutral (N), and Protective Earth (PE). A three-phase cable (for 22kW charging) uses five conductors: L1, L2, L3, N, and PE. Both cable types also carry two smaller signal wires, described below.
The pilot and PP wires you never see
A Type 2 single-phase EV cable contains two signal wires in addition to the power conductors: the Control Pilot (CP) and Proximity/PP wire. These implement the IEC 62196-2 communication protocol, allowing the car and charger to negotiate the available current before power flows. Without these wires functioning correctly, the charge session will not start.
This is worth knowing for a practical reason: if a cheap cable has damaged or poorly terminated pilot wires (as sometimes seen in low-quality marketplace purchases), the car may refuse to charge, or may charge erratically. The problem is inside the cable, invisible from the outside.
Sheath materials: TPU, TPE, and why PVC fails in winter
PVC sheath compounds become brittle below approximately 0°C and can feel almost rigid at -10°C, making them difficult to uncoil from the car or wallbox without risking the jacket. TPU (thermoplastic polyurethane) sheaths remain flexible down to -40°C, meaning a quality cable in a January frost behaves the same as in July. For UK outdoor use, TPU sheath is the baseline you should expect, not a luxury.
The three sheath materials compared:
- TPU (thermoplastic polyurethane): Flexible to -40°C, UV-resistant, oil and fuel resistant, highly abrasion-resistant. The best choice for year-round outdoor EV use.
- TPE (thermoplastic elastomer): Very similar to TPU in feel; sometimes slightly cheaper; good flexibility in cold but marginally less abrasion-resistant. Acceptable in quality cables.
- PVC: The cheapest option. Becomes stiff and brittle in cold weather, cracks under UV exposure over time. Not suitable for permanent outdoor EV cable use in the UK climate.
In our experience at EV Cable Hub, customers who contact us about stiff cables in winter are almost always holding PVC-sheathed cables, often sourced from marketplace listings that omit sheath material from the specification. For tips on keeping your cable in good condition through the colder months, see our guide on caring for your cable in winter.
Why weight is your best quality signal
Weight does not lie. Copper is roughly 30% denser than aluminium, so a CCA cable claiming to be 6mm² will be noticeably lighter than a genuine OFC cable of the same length. When you are buying online and cannot handle the cable before purchase, these approximate benchmarks for genuine 32A single-phase OFC cables give you a cross-check:
| Cable length | Approximate weight (6mm² OFC, 5-core) |
|---|---|
| 5m | ~1.5 kg |
| 10m | ~3.0 kg |
| 15m | ~4.5 kg |
| 25m | ~7.5 kg |
A cable significantly lighter than these figures for the same claimed spec is a warning sign. Reputable suppliers, including ourselves, are happy to confirm cable weight per metre and conductor material in writing. If a seller cannot or will not confirm this, treat that as important information.
For longer runs, the weight difference becomes an even more useful check: a 25m CCA cable will be dramatically lighter than a genuine 25m OFC cable of the same claimed cross-section. Our guide to longer EV charging cables (15m: 25m) includes further guidance on spec-checking longer cables before purchase.
Marketplace warning: “copper” cables that aren’t
The most common source of CCA cables in the UK EV market is mainstream online marketplaces, not a specialist bad actor. Amazon and eBay carry numerous listings for EV charging cables described as “copper” that contain CCA or in some cases predominantly aluminium cores with minimal copper cladding. The cables often look identical to genuine OFC products; the connectors, the jacket colour, even the plug mouldings can be indistinguishable.
What gives them away: - Low price relative to the market for the same spec (a quality 32A OFC cable at 5m should not cost £15) - Light weight: apply the benchmarks above - Vague or absent conductor specification in the listing, such as “copper cable” without stating cross-section, purity, or OFC/CCA designation - No reference to standards: quality cables cite BS 7671:2018+A2:2022 (IET Wiring Regulations), Section 722 compliance or equivalent IEC cable standards in their documentation
For guidance on keeping your cable physically secure once you have a quality one, see our guide to protecting your cable from theft. For a broader look at the standards that govern what a safe EV cable must comply with, our EV cable safety standards guide covers the full certification picture.
Frequently asked questions
What does OFC stand for in an EV cable?
OFC stands for oxygen-free copper. It refers to a high-purity copper conductor produced in a low-oxygen environment to reduce internal grain boundaries. This makes the conductor more flexible, more conductive, and less prone to work-hardening over repeated bending, which matters for a cable that is plugged and unplugged daily for years.
What mm² cable do I need for a 7.4kW home wallbox?
For a 7.4kW (32A single-phase) home wallbox, you need a cable with 6mm² copper conductors. A 2.5mm² cable is only safe up to 16A (3.7kW) and must not be used at 32A. It will overheat. BS 7671:2018+A2:2022 (IET Wiring Regulations), Section 722 specifies the cable sizing requirements that underpin this.
Is CCA safe for EV charging?
We do not recommend CCA (copper-clad aluminium) cables for EV charging. CCA has approximately 55% higher electrical resistance than copper, generates more heat at high continuous currents, and develops micro-cracks at repeated flex points over time. A CCA cable may pass initial use but degrade quietly, increasing resistance and heat generation across months of overnight charging cycles.
How can I tell if a cable contains genuine copper or CCA?
Weight is the most reliable field test. Copper is about 30% denser than aluminium, so a genuine 6mm² OFC cable will weigh noticeably more than a CCA cable claiming the same spec. A 5-metre 32A single-phase OFC cable should weigh approximately 1.5 kg. A cable of that specification that feels unusually light should be treated with caution.
Why does my EV cable get stiff in cold weather?
Stiffness in cold weather is usually caused by a PVC outer sheath. PVC compounds lose flexibility below 0°C and can feel almost rigid at -10°C. Quality EV cables use a TPU (thermoplastic polyurethane) sheath, which remains flexible down to -40°C. If your cable becomes hard to coil or uncoil in winter, the sheath material is likely PVC rather than TPU.
Do I need 10mm² cable for a 22kW three-phase charger?
For a 22kW three-phase installation, 6mm² conductors are standard for short cable runs. For longer runs, typically 15m or more, 10mm² conductors reduce resistive voltage drop significantly and are commonly used in commercial installs. See our guide to longer EV charging cables (15m: 25m) for detailed guidance on cable length and conductor sizing.
What are the pilot wires inside a Type 2 cable?
A Type 2 EV cable contains two signal wires in addition to the power conductors: the Control Pilot (CP) and Proximity/PP wire. These implement the IEC 62196-2 communication protocol, allowing the car and charger to negotiate the available current before power flows. Without these wires functioning correctly, the charge session will not start, so a damaged pilot wire in a cheap cable can cause intermittent charging failures.
Can I leave my EV cable outside overnight?
An EV cable with a TPU sheath and IP55 rating is designed for permanent outdoor use. IP55 means it is protected against rain and snow in normal outdoor conditions. Do not submerge the connectors. In our experience at EV Cable Hub, a quality TPU-sheathed cable handles year-round outdoor storage without degrading, whereas a PVC-sheathed cable left coiled outside through a UK winter will show cracking and stiffening within one to two seasons.