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What you need to charge your electric vehicle at home

By Shane Gilchrist |

Before you buy an electric vehicle, think about how you’ll charge it at home – and find out how much it typically costs to install a wall-mounted charging system

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As we continue to shift gears in to reduce our carbon outputs, and as more and more electric vehicles come onstream, there are costs to consider beyond the price tag on the window of the vehicle in the car yard.

Key questions to consider when buying an electric vehicle are how will you charge it, how much will it cost to install an EV charger at home, and what about those batteries, can you overcharge them?

Simple plug-in – or is more juice required?

Electric Car Charging

Yes, you can use a standard three-pin plug, which provides around 1.2kWh of charge. That’s okay for a hybrid or an EV with a comparatively small battery (and, therefore, lowish range), and will take your car from flat to fully charged on an overnight setting.

But for more juice, you might want a wall-box style charger, and these are becoming increasingly popular, says Gary Fuller, of Solcel Electrical Ltd in Dunedin, who is getting more and more enquiries about installing dedicated charging systems into both new and existing homes.

Fuller drives a seven-year-old Mitsubishi Minicab MiEV, powered by a 16 kWh lithium-ion drive battery, with a range of around 80kms. Using a low-powered charger, it takes Gary about eight hours to fully charge his van.

Were he to upgrade, Fuller says he would most likely steer towards a higher-spec smart charging unit. For example, the popular “Wallbox” Mode 3 single-phase charging station, rated at 7.4kW, which retails for around $2,000. It’s then around $2,000 for a straightforward install, although the price may increase if extra work and components are required to ensure your home’s circuitry can handle the output safely.

A safe earthing arrangement is a significant part of the installed system. Before a charging station is allowed to be connected to an electricity supply the installer needs to issue a certificate of compliance and an electrical safety certificate.

So, the approximate total of around $4,000 may hit the pocket but consider this. The average Kiwi household spent $48.50 on fuel each week in 2019, or $2522 per year, so it will take just a couple of years to recover the cost. But if you do a lot of driving, your sums could look quite different and a wall charger could pay for itself a lot quicker.

Standards New Zealand this year released this document covering EV chargers for residential use put together in consultation with transport, electrical, engineer and motor industry associations. It covers many of the angles you’ll need to know.

Charger type Use Time to charge Power
3-pin cable 230V single phase At home, can also take in the car as a back-up while out driving AC charge 12-14 hours AC: 1.75kW
Wall charger Fast charging at home Fast AC charge approx. 4 hours AC: 7-22kW
 

Built-in charging as the new normal

Electrician, Gary Fuller, says more and more new builds should feature integrated smart EV charging circuits. He points to recent electrical safety recommendations which recommend fully enclosed garage having a dedicated circuit for EV charging.

"It makes sense, because it’s easier and potentially cheaper to do in a new build than opening up wall cavities and changing mains and electrical boards, as is required for older homes. That said, people should consider a similar approach if they are looking to rewire or renovate an older house. Consider it an investment.”

Your home as an energy ecosystem

Smart charging offers a means of load management, both in terms of protecting your domestic circuits, but also helping safeguard our national electrical supply, by regulating best times (eg, off-peak) and how much load to take.

Find out about Genesis Energy’s EV off peak EV Plan

The electrical grid of the future is likely to feature demand flexibility, where your home functions as an energy ecosystem. This might include electricity users being paid to not use energy, a process known as demand response. For example, if you are planning to go on holiday, you might programme an app to notify your supplier, enabling them to better manage demand.

Switching from a vehicle that uses fossil fuels to one that uses electricity obviously requires consumers to think differently about refuelling. And given the majority of EV charging is expected to be done by private owners, it pays to think smarter about how you plug in at home.

FAQs

How much does it cost to charge an electric vehicle?

That depends on the time of day and how much charge you need. However, generally speaking, if you drive an average of 25-30km a day, the cost of charging an EV is about the same as paying 30c per litre for petrol. You can charge your EV overnight for about $3.00 per 100km, depending on the model and your electricity plan. A fast charge can cost up to $10 for 100km and takes about 20 minutes.

Should I charge my EV to 100%?

No need to charge to 100% consistently, unless you need to rely on the entire driving range of the vehicle. Staying between 20% and 80% battery capacity will leave you with plenty of driving miles and be gentle on the battery.

Is it bad to leave your electric car plugged in?

Once the systems in a typical EV detect that the battery is nearing a full charge, they should automatically slow down the charging process. The vehicle will use a technique called “trickle charging” to intelligently maintain a full charge in the battery without overdoing it. Onboard systems then dynamically monitor and allocate the charge as it’s needed.

How long does it take to charge an electric car at home?

The time it takes to charge varies greatly and is dependent upon the size of the battery and the speed of the charging. A typical electric car (60kWh battery) takes just under 8 hours to charge from empty to full with a 7kW charging point.

Will using a fast charger frequently ruin my EV’s battery?

Not all electric cars are compatible with fast charging. The Li-ion batteries used in old electric cars are not designed for fast charging, they have limited capacity, and their Battery Management System (BMS) is not programmed to manage fast charging. Fast charging is okay when the battery remains within 30-80% range, and the battery temperature remains between 0-30°C. It helps to have at least 24 hours between every fast charge.

What is a smart charging?

’Smart’ charging is where your EV charger has built in communication capability and is able to vary charging based on external signals. Smart charging allows you to increase or decrease your charging level and is often tied to the availability lower cost, off peak electricity.

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