EV Charger Wiring: Why #6 Copper Is Almost Always the Right Choice — Even When #8 Looks Cheaper

The situation

A homeowner in the GTA gets two quotes for a Level 2 EV charger install. Both contractors are licensed. Both quotes pass ESA inspection. The first quote is meaningfully cheaper. The homeowner picks it. Two years later, the same homeowner buys a new car — maybe a Tesla, maybe a different EV with a higher onboard charger — and wants to upgrade to a faster wall charger. They call back. The answer is uncomfortable: the wire that was installed two years ago can't support the new charger. The whole circuit needs to be redone. The "savings" from the original quote are gone, plus they're now paying for drywall repair, a new conduit run, and a second ESA inspection. This is the most common avoidable mistake in residential EV charger installations — and it almost always comes down to one decision: the size of the wire.

Why the wire size decision locks you in

Both #8 AWG copper and #6 AWG copper are legitimate wiring choices for an EV charger. Both can be installed by a licensed electrician. Both can pass inspection. But they support very different chargers, and most homeowners are never told there's a choice.

#8 copper supports a 40-amp continuous charger — typically a basic plug-in unit using a 14-50 outlet.

#6 copper supports a 48-amp continuous charger — the size of a Tesla Wall Connector and most modern hardwired Level 2 chargers on the market today.

The wire itself is roughly 50% more expensive in #6 than #8. But because the wire is only one part of an EV charger installation — alongside the breaker, conduit, ESA inspection, and labour — the total job cost difference usually works out to around 20%.

That 20% is the price of future-proofing your install. Skipping it can lock you into 40 amps for the life of the wire, and creates a potential fire hazard if anyone tampers with the circuit later without understanding what's behind the wall.

EV charger wire sizing under the Canadian Electrical Code

EV chargers are what the code calls a continuous load — any electrical load expected to run for three hours or more. EV charging easily falls into this category; a typical overnight charge runs four to eight hours.

For a standard residential breaker, the Canadian Electrical Code requires the continuous load to not exceed 80% of the conductor's ampacity — which is the same as sizing the breaker and conductor at 125% of the continuous load. So if your charger draws 48 amps continuously, the breaker and wire have to be rated for at least 60 amps. (CEC Rule 8-104(6)(a))

The decision

At Actus Electric, #6 AWG copper is the default for residential EV charger installations. We will install #8 if there's a specific reason — for example, a homeowner who has an older 32-amp charger they intend to keep and a clear understanding that the circuit cannot be upgraded later without rewiring.

But for almost every install, #6 is what we recommend. The labour cost is essentially the same. The wire pull takes slightly more effort, but the breaker, conduit work, panel work, and ESA inspection are identical. The added material cost is real but small in the context of the full install. The flexibility lasts the lifetime of the wire — 30+ years.

Before we recommend any EV charger install, we also review the home's panel capacity and historical electrical consumption to confirm whether the existing service can safely support the new charger — or whether a service upgrade should be planned alongside it. The 20% cost difference for #6 wire is a one-time payment. The 40-amp limitation lasts forever.

What most people get wrong

The fire risk is not from the original install — it's from what happens later.

A properly installed 40-amp circuit on #8 copper, with a 40-amp breaker and a charger configured for 32-amp output, is safe. The real hazard appears when the homeowner later upgrades to a more powerful charger. A homeowner — or a less careful contractor — may swap the breaker to 60 amps to support the new charger without rewiring. At that point, the #8 wire is carrying continuous current well above its rating. Insulation degrades. Connections heat up. This is a potential fire hazard, and it doesn't show itself until the wire has been overloaded for some time.

Most contractors don't offer a choice of wire size. They quote what produces the most competitive number, which is almost always #8 with a 40-amp breaker. The customer rarely hears the word "amperage" until they call back two years later asking about a Tesla upgrade.

In new construction or major renovations where conduit is being run anyway, it costs almost nothing extra to pull #6 — and it sets the home up for any EV the family chooses to drive over the next decade.

Conclusion

A cheaper EV charger quote isn't always a worse quote — but if the only reason it's cheaper is because the wire is undersized, the savings are temporary. The wire stays in the wall for the life of the home. The charger doesn't.

Any electrician who knows their work will give you a clear answer in plain English when you ask about wire size and maximum continuous amperage — and explain why.