Two quotes land in a North Shore homeowner’s inbox. Both appear to cover the installation of the same EV charger. One costs considerably less.
From the customer’s perspective, the choice looks straightforward. Why pay more for the same charger on the same garage wall?
But the two electricians may not be quoting the same installation at all.
DCN Electrical has lost EV charger installation jobs because another quote allowed for 4 mm or 6 mm cabling while ours specified a larger cable. The difference is rarely obvious from the total at the bottom of the quote. It may be hidden in a single line describing the new circuit—or not explained at all.
That cable will carry a substantial electrical load, often continuously for hours, every time the vehicle charges. Once it disappears through the walls, ceiling or underground conduit, the homeowner is left with the consequences of the decision.
That is why EV charger cable size in Sydney should never be reduced to whichever option produces the cheapest quote.
A cheaper quote may contain less electrical capacity
Cable costs money. Larger cable costs more to purchase and can be more difficult to route, terminate and install.
Using 4 mm or 6 mm cable can therefore reduce the quoted price. That gives an electrician a commercial advantage when a homeowner is comparing totals without seeing the design behind them.
The smaller cable is not automatically unsafe in every possible installation. A short circuit supplying a charger operating at a lower current may have different requirements from a long run supplying a 32-amp charger.
But that is precisely the point: cable size must be selected for the actual installation. It cannot be chosen simply because it is cheaper or has been used successfully somewhere else.
DCN Electrical considers the charger’s requirements, maximum demand, cable route, installation method, circuit length, voltage drop, protective devices and the conditions surrounding the cable. A cable enclosed in insulation or grouped with other circuits will not dissipate heat in the same way as one installed in open air.
If your quotes vary significantly, ask DCN Electrical to compare their scope—not just their final prices. We can explain what has been allowed for and whether you are genuinely comparing the same EV charger installation.
Why an EV charger exposes shortcuts that other appliances may not
A household circuit does not necessarily carry its full rated load for hours at a time. An EV charger often does.
The car can begin charging after everyone goes to bed and continue drawing power through the night. The cable must carry that sustained load repeatedly, not just survive a brief peak.
When a cable is too small for the current and installation conditions, its operating temperature can rise. Excessive heat can damage insulation, weaken terminations and increase the risk of electrical failure. An undersized circuit can also produce excessive voltage drop or require the charger to be restricted below the performance the owner expected.
The problem is not always announced by an immediate fault. The charger may appear to work. The cable is concealed, and the customer cannot see what happens along the run each night.
That makes the design decision more important—not less.
EV charger cable size in Sydney depends on the entire route
Asking whether 6 mm cable is suitable for an EV charger is like asking whether one pair of shoes will fit every person. The number alone does not provide enough information.
Consider two North Shore installations using the same wall-mounted charger.
In the first home, the switchboard is on the opposite side of the garage wall. The cable run is short and accessible.
In the second, the switchboard is at the front of the house while the garage sits at the rear. The circuit must pass through a crowded ceiling, near insulation and down an external wall before reaching the charger.
Those installations may look identical when finished. Electrically, they are not.
DCN may specify 10 mm or 16 mm cable where the length, load, installation method or manufacturer’s instructions require it. That is not an automatic prescription for every home. It is the result of designing the circuit around the installation that actually exists.
A quote that simply states “install customer-supplied EV charger” does not tell you:
- the proposed cable size;
- the maximum charging current;
- the cable length used in the calculation;
- how the cable will be installed;
- the voltage drop allowed for;
- whether the switchboard can support the additional demand;
- which circuit protection is included; or
- whether the charger manufacturer’s installation requirements have been followed.
If those details are missing from your quote, you are entitled to ask for them before accepting it. DCN Electrical can assess your North Shore Sydney property and provide a quote based on the actual cable route and charger—not a generic allowance.
The Wiring Rules are not permission to ignore the charger manual
Australian electrical requirements and the manufacturer’s instructions must be considered together.
An electrician cannot use a manufacturer’s manual to justify work that fails Australian requirements. Equally, meeting a minimum cable calculation does not necessarily justify ignoring an additional requirement specified by the charger manufacturer.
Manufacturers design and test their equipment around stated installation conditions. Those conditions can include supply arrangements, conductor requirements, protective devices, torque settings, isolation and commissioning procedures.
Departing from those instructions may affect the safety or performance of the installation. It can also give the manufacturer grounds to reject a warranty claim connected with an installation that did not meet its documented requirements.
The question is therefore not: What is the smallest cable we can legally install?
It is: What cable does this charger require on this circuit, through this house, under these installation conditions?
That is the question DCN Electrical answers before choosing the cable.
A charger warranty does not cover the cable inside your house
The charger manufacturer warrants its equipment subject to its warranty terms. It does not take responsibility for every design decision made by the installer.
If the charger develops a fault, the installation may be examined. A circuit that does not follow the manufacturer’s requirements can complicate the claim, particularly where the fault may be connected with the supply, voltage drop, overheating or incorrect protection.
Even if the charger itself is replaced, that does not correct an unsuitable cable concealed through the property.
The expensive part may be accessing and replacing the circuit after the walls are finished, the ceiling is insulated or the landscaping has been completed.
If DCN’s quote includes a larger cable than another electrician’s, ask us why. We would rather show you the calculation and installation considerations now than have you discover the difference after the circuit has been concealed.
Why DCN will not reduce the cable merely to win the quote
We understand that price matters. An EV charger and electrical installation represent a significant purchase, and nobody wants to pay for something they do not need.
But there is a difference between removing unnecessary cost and removing electrical capacity required by the design.
DCN Electrical will not substitute a smaller cable simply to make our figure look better beside another quote. If our assessment shows that a larger cable is required, we will price that cable and explain the reason for it.
Sometimes that means we lose the job.
It also means the price we provide reflects the installation we are prepared to complete, test and stand behind. We do not rely on the fact that the cable will soon be hidden from view.
Compare the circuit before comparing the totals
Before choosing an EV charger installer, ask each electrician the same questions:
- What cable size is included?
- What maximum charging current has the circuit been designed for?
- How long is the proposed cable run?
- Has the installation method been considered?
- What voltage drop has been allowed for?
- Does the design follow the charger manufacturer’s instructions?
- What circuit protection is included?
- Will I receive the required electrical compliance documentation?
The answers should reveal whether the lower price comes from greater efficiency—or simply a different scope.
A detailed quote may cost more because it includes more cable, a difficult route, switchboard work, load management or protection that the cheaper quote has not allowed for. Until those differences are exposed, the totals are not meaningfully comparable.
DCN Electrical installs EV chargers across Sydney’s North Shore and can assess the charger, switchboard and proposed route before recommending a circuit design. Enquire if you want a quote that explains what will be installed rather than hiding the important detail in the walls.
Frequently Asked Questions
Is 6 mm cable large enough for an EV charger?
Sometimes, but not automatically.
Its suitability depends on the charging current, circuit length, cable type, installation method, surrounding temperature, grouping, thermal insulation, voltage drop and charger manufacturer’s requirements.
A statement that 6 mm cable is “good for an EV charger” is incomplete unless it identifies the charger and installation conditions. DCN assesses the whole circuit before confirming the cable size.
Do all 7 kW home EV chargers need 10 mm² cable?
No single cable size applies to every 7 kW charger installation.
Although a single-phase 7 kW charger commonly operates at about 32 amps, current alone does not determine the cable. A short, openly installed cable run may produce a different result from a long circuit passing through insulation or a hot roof space.
The manufacturer may also specify requirements that must be incorporated into the design. DCN may use 10 mm or larger cable when the complete assessment supports it, but we do not prescribe it without inspecting the installation.
Can incorrect EV charger cabling affect the warranty?
It can.
Manufacturers commonly require their chargers to be installed according to their instructions and applicable electrical requirements. If the specified installation conditions were not followed, the manufacturer may question or reject a claim connected with the installation.
If you already have a quote and are uncertain about its cable allowance, DCN Electrical can review the proposed scope before the work begins. It is much easier to resolve the question before the cable is installed and concealed.
Why does one EV charger installation quote cost more than another?
The quotes may include different cable sizes, circuit lengths, protective devices, switchboard work, installation routes, load-control equipment or commissioning work.
One electrician may have inspected the proposed route and priced the circuit it requires. Another may have included a standard allowance that changes once work begins—or specified smaller cable to reduce the initial price.
Ask both electricians to document what is included. A price comparison is useful only when the electrical scope is genuinely the same.
The cable matters long after the quote is forgotten
The EV charger is the part you see. The circuit supplying it is the part expected to carry a sustained electrical load, night after night, for years.
Choosing the correct EV charger cable size in Sydney is not about automatically installing the largest available cable. It is about selecting the right cable for the charger, route, load, installation conditions and manufacturer’s requirements.
The cheapest quote may still be good value—but only after you establish what it includes.
If you are planning an EV charger installation on Sydney’s North Shore, contact DCN Electrical for an assessment and itemised quote. We will explain the proposed cable and circuit design so you can compare the work, not merely the number at the bottom of the page.
