Understanding the options for charging an electric vehicle (EV).
Unlike refuelling an internal combustion vehicle, where your choices are limited mainly to which brand of service station you refill at, battery electric vehicles (BEVs) can be charged either by an AC charger at home or by AC and DC chargers at public charging stations.
Each method has its pros and cons regarding cost and convenience, with the main differentiator being the time it takes to charge.
In general terms, the larger an EV’s battery, the longer it will take to charge, with the power output of the charging device being the key.
However, battery type/chemistry and whether the vehicle can accept 400V or 800V charging also have an influence.
This is the simplest and most readily available EV charging option since all you need is a power socket and the charging lead supplied with your EV.
A regular household socket delivers 10 amps of electric current, giving a total charging capacity of 2.3 kilowatts.
This means you can charge an EV at a rate of just over 2kW from a standard socket. Given our AC charging workload of roughly 2kW per hour, a 60kWh battery will take about 30 hours to charge from empty.
That equates to about 12km of range for every hour of charging.
In this scenario, if you plug and recharge every night, which most EV owners prefer, you are replenishing only a fraction of the total battery capacity for each charge.
The charging cycle is not consistent, and charging takes longer as the battery gets closer to capacity.
Temperature, be it ambient or battery, will also affect charging time.
The next level of charging is the home wall box, a piece of charging equipment often installed in household or apartment garages to facilitate faster charging than the 10-amp household socket.
Most EV makers sell wall boxes as an optional accessory, or they can be purchased from independent charging specialists, priced from about $1,000 and $800 for installation.
There are two options with wall boxes, either sticking with standard single-phase power or upgrading to a more powerful three-phase system.
A three-phase circuit provides greater power density than a single-phase circuit at the same amperage, transmitting three times as much power, meaning faster charging times. However installation of three-phase power can be costly and may not be available in your street.
A wall box connected to single-phase power charges at a rate of 7.2kW, which brings EV charging time down significantly and makes it possible to charge most batteries overnight.
Using our standardised 60kWh battery, charging this way will deliver a flat-to-full charge in about eight hours.
That equates to about 42km for every hour of charging.
The next option is to step up to a wall box connected to three-phase power with a charging rate of up to 22kW.
Using our 60kWh battery again, this will deliver a flat-to-full charge in about three hours or about 130km of range for every hour of charging.
Before going to the trouble and expense of installing three-phase power, it’s worth checking the specifications of your EV to ensure it’s able to charge at 21kW from an AC supply since some EVs will only charge at a maximum of 7.6kW AC, even with a 22kW charger.
Most public chargers are currently AC chargers that vary in charging capacity (and speed), so it’s helpful to know in advance if the charger you plan on using is a 7.2kW or 22kW unit.
DC fast charging is currently the gold standard for charging speed and efficiency. These chargers are increasingly being deployed at major highway rest stops and filling stations to facilitate efficient long-distance EV travel.
The RACQ-sponsored Queensland Electric Super Highway (QESH) is a network of 31 fast-charging sites from Coolangatta to Port Douglas, with 18 more to be added in outback locations. The QESH was constructed by Yurika which is part of Energy Queensland.
DC fast chargers range in capacity from 50kW to 350kW, although not all EVs can charge at this capacity, with the vehicle’s onboard systems moderating how much charge they can accept.
Many late-model vehicles with larger batteries and more sophisticated battery cooling systems, such as the Hyundai Ioniq 5, Tesla Model S and Audi e-Tron, can use the higher power capability of these chargers.
However, many smaller-capacity EVs, including the Nissan Leaf and MG ZS EV, can’t use such high-charging capacity, so while they can be charged on 100kW or 250kW DC fast chargers, they will only charge at a rate of 50kW.
Using our standardised 60kWh battery and the more widely available 50kW DC fast chargers, the battery will be replenished in just over an hour. A one-hour charge will deliver about 300km of driving range.
Constantly charging at high speeds on DC chargers will increase the rate of battery degradation over time.
Another EV charging option attracting growing interest is the use of household solar and a battery storage system.
This is the ultimate solution for those consumers purchasing an EV for environmental reasons. It means they are charging their zero tailpipe emissions vehicle from a zero-emissions energy source.
In Queensland, many home solar power systems will create more electricity than households use. The system’s inverter sends the excess electricity back to the grid when this occurs.
However, because solar feed-in tariffs have fallen considerably in recent years, it’s becoming less economically viable to export excess solar to the grid, given the electricity must be purchased back at night at a higher rate than the feed-in tariff.
This is prompting homeowners to invest in battery storage, which stores the excess energy generated during the day for use in their homes at night, and to charge EVs during the day.
In Queensland’s sunny climate, a solar battery storage system may be full by mid-morning, allowing users to charge their EV for part of the day and still store enough energy to run the household at night.
Like solar installations, the cost of battery storage systems has fallen significantly in recent years, to the point where installing such a system is now a viable option for many Australian households.
The information in this article has been prepared for general information purposes only and is not intended as legal advice or specific advice to any particular person. Any advice contained in the document is general advice, not intended as legal advice or professional advice and does not take into account any person’s particular circumstances. Before acting on anything based on this advice you should consider its appropriateness to you, having regard to your objectives and needs.