Getting your home ready for an EV charger — what the electrician checks before installation

A home EV charger is a significant electrical load. A 7.4 kW charger running on a 32A circuit is pulling more current than most ovens. Running that reliably, safely, and within the standards requires the existing electrical infrastructure to be up to the task. A lot of homes in Melbourne's eastern suburbs — particularly those built before 2000 — aren't quite there by default.

This isn't a reason to delay buying an EV. It is a reason to get a proper assessment before you commit to a charger model or installation quote. Here's what we look at, and why it matters.

Switchboard capacity

The first question is whether your switchboard has a spare circuit position and enough total capacity to absorb a 32A circuit without constantly tripping the main switch.

Most modern switchboards in Victoria are rated at 63A or 80A single-phase, with a 100A main switch being common in homes with multiple large loads. The usable headroom on a 63A board running a 12kW ducted system, electric oven, and hot water service is limited. Adding a 32A EV charger pushes it.

We look at:

• Total installed circuit breaker capacity: the sum of all breaker ratings on the board. This isn't the same as actual peak load, but it gives a picture of what the board was designed to handle.
• Main switch rating: the rated capacity of the main switch itself. If it's a 63A main switch on a board that's already heavily loaded, we may need to upsize it.
• Available spare positions: whether a physical circuit position exists for the new circuit, or whether a board upgrade is needed to create space.
• Age and condition of the board: older boards with ceramic fuses, no safety switches, or deteriorating busbars need upgrading before we add a major new load.

A switchboard upgrade before or alongside the EV charger installation is more common than most people expect. It's not a failure of the existing installation — it's the cost of adding load the original installation wasn't designed for.

Consumer mains assessment

The consumer mains are the cables that run from the electricity distributor's infrastructure (the service fuse in the meter box) into your switchboard. They are the single most important constraint on your home's electrical capacity, and they're also the one thing you cannot change without involving the network distributor.

In Melbourne, older homes commonly have 16mm² or 25mm² aluminium consumer mains. The ampacity of these cables — their current-carrying capacity — determines the maximum load your property can draw before the supply fuse opens. A 16mm² aluminium mains typically supports around 63–80A depending on the installation method. That's fine for most households, but becomes tight once you factor in an EV charger.

We measure or verify the size of your consumer mains during the assessment. If the mains are undersized for the total connected load you want to run, the solution is a mains upgrade — which requires a disconnection, new cable, and coordination with the distributor. This is something to know about before you buy the charger, not after.

Earthing adequacy

AS/NZS 3000 (the Wiring Rules) requires the protective earthing system to be effective. For an EV charger specifically, this matters because the charger communicates with the vehicle over the earth conductor and uses it for fault protection. A poor or corroded earth stake, deteriorated earth bonding, or missing main protective conductor will fail the charger's self-test or create a genuine safety hazard.

During the assessment we check:

• Earth electrode resistance (where accessible)
• Main earthing conductor size and condition
• Equipotential bonding at the meter box and switchboard
• RCD protection — a 30mA RCD is required on the EV charger circuit under AS/NZS 3000, and Type A or Type B RCDs may be specified depending on the charger's DC fault injection characteristics

Most EV charger manufacturers specify Type B RCDs in their installation manuals. A Type B RCD is substantially more expensive than a standard Type A, and it's not always stocked by wholesalers — worth factoring into the budget.

Cable run from switchboard to garage

The further the garage is from the switchboard, the more the cable run costs — and the more it needs to be sized up to keep voltage drop within the 5% limit specified in AS/NZS 3000.

A 32A circuit running 20 metres in 6mm² TPS (twin and earth) is fine. The same circuit running 40 metres needs 10mm² to keep voltage drop acceptable. At 60 metres, you're looking at 16mm² or reconsidering the routing.

We measure the actual route — not the straight-line distance — during the assessment. The difference between a clean surface run in conduit and a route that goes underground, through the ceiling cavity, and out through the wall can be significant both for cost and for what cable size is practical.

Routing through existing conduits is sometimes possible in newer homes. In older homes it rarely is. The route through the wall, under the patio, and into the garage is more often the reality.

Single-phase vs three-phase supply

Most Melbourne homes are single-phase. A 32A single-phase circuit delivers 7.4 kW of charging — which charges most EVs overnight without any issue. For most households, single-phase is the right answer.

Three-phase supply, where available, enables 11 kW or 22 kW AC charging using a three-phase charger. This is genuinely useful for households with two EVs, high daily kilometres, or those who want the car fully charged in a few hours rather than overnight.

The question is whether your property has three-phase supply. Many homes in Melbourne's eastern suburbs don't — the local network infrastructure doesn't always make it available. If you want three-phase and it's not connected, you need to apply to your distributor (CitiPower or United Energy depending on the area) for a supply upgrade.

In Victoria this process is handled through what's known as a Distributed Customer Batch Vendor (DCBV) application for large supply upgrades, or a standard augmentation application for three-phase connections. It involves a design and quote from the distributor, a connection agreement, and network augmentation work if the local infrastructure needs upgrading. Costs range from a few thousand to significantly more depending on what the network needs to do. Timeframes are typically two to six months.

This is worth understanding before you purchase a three-phase charger that your single-phase property can't use.

Load management for homes near their limits

If the assessment shows your home is close to its supply limit but doesn't need a full mains upgrade, load management is worth considering.

Load management — sometimes called dynamic power sharing or smart charging — uses a current transformer (CT clamp) on the consumer mains to monitor the total load entering the property. When the household load is high, the charger automatically reduces its output to stay within the supply limit. When the household load drops, charging resumes at full speed.

This approach means you can install a 32A charger circuit on a property where running it at full tilt simultaneously with everything else would exceed the mains rating — because in practice, you rarely run everything simultaneously.

The practical requirement is that the charger supports load management and is compatible with the CT clamp and communication system you're using. Not all chargers do. This is a consideration for the charger selection, not just the electrical installation.

What the assessment produces

A proper pre-installation assessment gives you a clear picture of:

• What the installation will actually cost (not just the charger and its immediate wiring)
• Whether a switchboard or mains upgrade is needed, and if so, approximately what it costs
• What charger capacity is practical for your home's current infrastructure
• Whether three-phase is available and worth pursuing
• What load management approach, if any, is appropriate

This is the conversation to have before you commit to a brand of charger or a specific model. Some chargers are only available in 22 kW three-phase versions. Some load management systems only work with specific charger brands. Getting the electrical picture first means you buy a charger that works with your home, rather than retrofitting the home around a charger you've already ordered.

If you want an EV charger assessment before you buy, get in touch with us through the EV charger page and we'll come out and walk through it.