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As electric vehicles (EVs) continue to enter our homes at a rapid rate, customers need guidance for charging solutions. Sean Carroll writes about how to start that conversation with residential customers.

The future of transport is electric, and while Australians are slowly adopting the new technology, there’s still a lot of work to be done on the infrastructure side.

One of the main barriers to entry for EVs is range anxiety and drivers being sure that their vehicle can reliably get from point A to point B. It’s possible across much of the country but as the infrastructure grows, the next point of concern is going to be ensuring there’s enough power going around to charge all of these vehicles at once.

The Electric Vehicle Council (EVC), the national body representing the EV industry in Australia, believes that this is a pain point that can easily be avoided if the people installing the charger – electricians – are fully aware of the different solutions and methods.

“One of the most important roles for electricians in this area is education,” EVC head of energy and infrastructure Ross De Rango explains.

“Consumers buying their first EV today are usually not electricians or engineers – they don’t necessarily understand power, energy, amps or kilowatts; they just need a reliable solution, at a price they can afford that’ll meet their needs.”

He says that an electrician who knows what they’re talking about can be a trusted advisor to the consumer, helping them make the right choice about an EV charging solution that performs well.

To do this, the electrician needs to determine the maximum demand. This is the peak expected load in an electrical system. It’s determined at the time of design or modification to the electrical system, in order to inform the required capacity of upstream electrical equipment in accordance with section 2.2.2 of AS/NZS 3000:2018, the Wiring Rules.

It’s important that sparkies get this step right because if a determination is incorrect, the installation could be more expensive than necessary, but if it’s underestimated, circuit breakers will trip and fuses may blow.

The EVC believes that there are two methods in the Wiring Rules that are best suited for determining the maximum demand as part of an EV charger installation for standalone dwellings in a residential environment: calculation and limitation.

Calculation (Method A)

This first method is the most common in determining maximum demand during design for the electrical industry. It’s done by projecting all the individual loads under consideration, with reference to tables in Appendix C of the Wiring Rules.

This approach gives electricians a conservative estimate of what would happen if a significant proportion of the equipment in an installation were used at the same time. It doesn’t factor in the opportunity to limit the maximum demand by controlling individual loads, such as using the EV charger at certain times of the day.

In the case of EV charging for domestic installations of up to five dwellings, the calculation method assumes that the EV charger always uses 100% of its maximum load. This means that a 32A charger will add 32A to the maximum demand contribution.

For a standalone dwelling with a 63A supply, if the intent is to install a 32A (7kW) charger, the final calculation is likely to exceed 63A once adding in the oven, aircon, hot water service and so on. Because of this, the electrician will probably recommend that the end user upgrade the supply to the building.

This is a much lengthier and more expensive solution. Depending on the site, it might also lead to the conversion of meters, fuses and main switchboards from single to three-phase.

“Upgrading a standard domestic home from a single phase to three-phase will typically cost around $3,000 to $4,000,” Ross says.

“It means a truck roll from the network, a new energy meter, a new incoming supply protection device and typically a new main switchboard. Individual homes will vary, and different networks have different rules and fee structures around this transition.”

If the upgrades are made, it’ll ensure that the dwelling has a higher availability of charging which may be more suitable to the end user if they’re willing to pay the additional costs.

It’ll be costly, but the driver will be able to charge the car at full power at any time. The downside is that to the extent that drivers choose to charge their cars at peak times, they’ll create a need for more network augmentation in the energy networks. Drivers charging their cars at peak times will also typically pay more for energy than drivers choosing to avoid peak times for charging their cars.

“This approach leads to higher costs. Consumers installing 22kW three-phase EV chargers at home and running them at peak time just because they can, contributes to higher costs for everyone,” Ross says.

It may be necessary for some users to charge at these times, but given typical working hours, the excess costs for the driver and the energy system can be avoided with the next method.

Limitation

With this approach, the electrician can install a circuit breaker to define the maximum demand by limiting the maximum current. This method is particularly suitable for standalone houses, such as those equipped with a 63A main switch and backed up with 80A service fuses.

To apply the limitation method to an electrical installation, the electrician must:

• Replace the 63A main switch with a 63A circuit breaker or install a 63A circuit breaker in series with the 63A main switch. Which of these is more practicable will be governed by the specific site installation and the local service and installation rules.
• Inform the consumer that they should use the EV charger when other high-energy equipment (oven, aircon, etc.) are not in use simultaneously. They can do this by setting their preferred charging time in the vehicle, via an app that communicates with the car or just by remembering to plug the car in when they go to bed.
• Show the consumer how to reset the breaker, in case they forget, and try to charge their car while running everything else.

“EVs can easily be set to charge at specific times and this technology is highly reliable,” Ross says.

“If we assume that the driver chooses to set the car to charge between 11pm and 7am, and has a 32A single-phase charger, they’re looking at eight hours charging at 7.4kW, so about 60kWh. That’s enough for about 350km of driving in most EVs.”

He adds that the actual amount delivered is limited by how big the battery is but it’s more than enough for a few days’ commute to work or a weekend away.

In a worst-case scenario, if the user were to charge their EV while other energy-intensive devices are in use, the new 63A breaker may trip but the fuse (which the consumer can’t replace by themselves) would not.

The normal behaviour of an EV driver isn’t to run the car empty and then plug it in. Most EV drivers charge the car at home several times a week but if they need to take the EV out at a non-routine time, there will be fast charging stations available wherever they go, so it’s not a disaster if they forget to charge it overnight.

It’s not like petrol cars are typically driven until the tank is completely empty before filling up. The same is true for EVs – except that with at-home EV charging, topping up is easy, so the car in the driver will usually be at least half full.

Limitation is the easier of the two methods and it’s significantly cheaper for the end user. It requires only a small modification, the addition of a miniature circuit breaker (MCB) in the main switchboard in series with the main switch.

The key to this method is educating the driver, making sure that they’re not using the EV charger while everything else is running. The best way to do this is to charge the EV at off-peak times – either middle of the day when the solar panels are producing lots of energy and not much else is running in the house, or overnight when everyone’s in bed and there isn’t multiple energy-intensive devices working all at once.

“Thinking of it like plugging in your phone before bed is a useful analogy for EV drivers,” Ross says.

“It’s worth noting that with a 63A supply, nothing stops the consumer from charging at peak time if they decide to. The only difference is that they won’t be able to charge the car while also running multiple other appliances at the same time – the oven and the EV charger at the same time will be fine, but adding the oven, the aircon, the hot water and the EV charger together would put the supply over the limit. 63A is a lot more than a typical domestic home needs anyway.”

On the network side, if people are encouraged to charge their EVs at off-peak hours, there will be less strain on the energy network. As Ross explains, this could even lead to cheaper electricity for the EV: “Almost everywhere across Australia, there’s always cheaper electricity available in the middle of the day and the middle of the night.

“Happily, consumers are already self-managing their charging to a significant degree. Australians prefer to use their own solar to charge EVs and they prefer to pay less for electricity rather than more so it’s an easy incentive to charge at these times.”

The Electric Vehicle Council (EVC) occasionally publishes guidelines to help the electrical trade keep up with the changes and make sense of the EV world.
If readers have a question that isn’t already covered by this article or something the EVC has already covered, you can ask them a question at office@evc.org.au.