EV charger circuits need cable sized for current, voltage drop, installation method and protection. Outdoor and underground runs often use steel wire armour (SWA) or other suitably protected cables in containment. The longest or hardest route usually drives labour cost more than the wallbox sticker price. A survey should state cable type, route and reinstatement assumptions in writing.
Why cable choice is a design decision
Current-carrying capacity changes with clipping direct, conduit, insulation surround and ambient temperature. Voltage drop over long garden runs can force a larger conductor than a short garage hop. Installers calculate this; catalogue ampacity tables alone are not enough.
Manufacturer terminals also limit acceptable conductor sizes and types. The charger model and the cable design must agree.
- Ask for approximate route length on the quotation.
- Confirm whether underground sections are included.
- Clarify who reinstates turf, resin or block paving.
Where SWA earns its keep
SWA provides mechanical protection for buried or vulnerable outdoor routes. It still needs correct termination, glands, earthing of armour where required, and suitable depth or additional protection according to the installation method.
Surface clipped SWA along walls can be appropriate, but appearance and fixing into finished facades may push designers toward alternative containment on visible elevations.
Civil works hide inside cable prices
Trenching across a long resin drive differs from a shallow border trench in soil. Shared surfaces, tree roots and unknown utilities add risk pots that honest quotes disclose as provisional where needed.
Sometimes a longer surface route along a fence is cheaper overall than a short diagonal trench through premium paving. Ask for that comparison when aesthetics allow.
Internal routes and fire stopping
Cables passing through walls, floors and fire-resisting construction need appropriate sealing. Flats and houses converted into multiple dwellings deserve extra care.
Neat white trunking is not automatically compliant containment. Method matters more than appearance, though both can be achieved together with planning.
- Avoid DIY buried twin-and-earth shortcuts outdoors.
- Record buried route depth and path for future landscaping.
- Keep spare draw capacity in ducts if a second circuit is likely.
Frequently asked questions
Is SWA always required for outdoor EV chargers?
Not always, but outdoor and buried sections need a protection method suited to the risk. SWA is common; other compliant approaches exist when designed correctly.
Why is my cable cost higher than a neighbour's?
Route length, surface type, voltage drop sizing and access usually explain it. Comparing wallbox brands alone misses the expensive part of the job.
Can cable run inside the house then exit near the car?
Yes, and that can reduce underground work. Fire stopping, aesthetics and drilling through finished rooms still need agreement.
Should I install an empty duct for the future?
Often wise when groundworks are open for other reasons. Confirm duct size, draw cord and bend radii suitable for later EV cable pulling.
Core buying guides
Start with these high-intent guides, then dig into the rest of the library.
Related guides
Sources and further reading
How this guide was prepared
This guide was written by the Local EV Installers Editorial Team. We compare official guidance, legislation and established consumer information, separate general information from project-specific advice, and show publication dates and sources. We do not accept installer accreditation claims at face value.