What size cable and circuit does an EV charger need? For a typical 7kW home charger the honest answer is "usually 6mm² cable on a dedicated 40A circuit with its own safety switch" — but the real answer depends on the cable run and how it's installed, which is exactly why an electrician calculates it rather than guessing. Here's what drives it.
The starting point: how much current the charger draws
- 7kW single-phase charger — draws about 32A. Commonly wired with 6mm² copper on a dedicated circuit protected around 40A, with an RCD (safety switch).
- 22kW three-phase charger — draws about 32A per phase. Needs a three-phase circuit, typically 6mm² per phase as a baseline, on a three-phase breaker with RCD protection.
- A portable "granny" charger on a 10A power point draws about 10A — no new circuit, but very slow and not for daily use.
Why the cable run changes everything
Those are baselines, not promises. The longer the cable run from your switchboard to the charger, the more the voltage drops along the way — so a long run (say a detached garage down the yard) often needs a larger cable than the minimum to keep the charger running at full power and stay within the wiring rules. How the cable is installed matters too: cable bunched in insulation or conduit can't shed heat as easily, so it may need to be upsized. This is the calculation (to AS/NZS 3008 and the wiring rules) that a proper electrician does before quoting.
If someone quotes a cable size over the phone without knowing your run length and switchboard, be cautious — undersized cable on an EV load is a genuine safety and performance problem.
Does your switchboard have room?
A dedicated charger circuit needs a spare slot and enough spare capacity on the board. Older or full boards sometimes need an upgrade first — signs you need a switchboard upgrade covers this. And if you're weighing 7kW against 22kW, our 7kW vs 22kW guide will save you money most of the time.
We assess the run, the board and your car up front, so the cable and circuit are sized right — no surprises on the day. Get a free assessment.
Common questions
What size cable does a 7kW EV charger need?
A 7kW single-phase charger draws about 32A and is commonly wired with 6mm² copper on a dedicated ~40A circuit with a safety switch. Long cable runs or heat-affected installs often need a larger cable, so an electrician calculates it for your home.
What circuit does a 22kW three-phase charger need?
A 22kW charger draws about 32A per phase and needs a dedicated three-phase circuit with RCD protection, typically 6mm² per phase as a baseline and larger for long runs. It also needs three-phase power at the property.
Does the cable run length affect the cable size?
Yes — the longer the run, the more voltage drops along it, so long runs (like a detached garage) often need a bigger cable than the minimum to keep the charger at full power and meet the wiring rules.
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