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Aug 02, 2023

When should I choose a dedicated home EV charger over a power point?

Most electric vehicle owners will do most of their charging at home – at least those with access to off-street parking. But a big question for many new to the technology is what sort of home charging

Most electric vehicle owners will do most of their charging at home – at least those with access to off-street parking.

But a big question for many new to the technology is what sort of home charging facilities they need: Do they need to install a dedicated wall charger, or will a standard plug do the job?

In countries that use three phase electricity supply systems, there are three options for EV charging – these are referred to as Modes 2, 3 and 4, as shown in Figure 1 below.

Mode 2 is where you plug a portable charger – that usually comes with the car – into a standard power point.

Mode 3 chargers are permanently fixed in position and directly wired. Whilst Mode 3 chargers generally provide higher charging speeds than Mode 2, this is not entirely true as you can buy portable chargers to use with bigger power outlets than can charge as the same rates as any Mode 3 charger. (More on that later).

I am leaving Mode 4 out of this discussion of home charging as even the smallest DC charger requires way more power than most home electricity connections are capable of delivering.

So the choice comes down to using a power point for EV charging (Mode 2) or installing a dedicated wall charger (Mode 3).

The first thing to note is that there is nothing wrong with regularly using the same power point for EV charging (as opposed to occasional use).

You do need to make sure that:

A: The power point is in good condition and installed as per the Wiring Rules for outlets used for EV charging. (In summary, it is wired direct to the switchboard on its own circuit).

B: You do not need to charge a lot. One to four hours a couple of times a week is a good rough yardstick for ‘not a lot’. It is worth noting here that most portable chargers now supplied with the car charge charge at a rate of 1.8 kW – earlier ones were up to 2.4kw (although you can still buy aftermarket ones that do 2.4 kW).

At 1.8 kW, you will get around 12 km charger per hour – or around 50 km in a four hour period – see Table 1 below. If you regularly charge for longer than four hours though, you might bump into not being able to charge at the cheapest electricity tariff all the way through the charging period.

This especially applies if you need to charge for longer times, as most off-peak tariffs max out at around eight hours. Six to eight hours is also roughly the time of highest solar output if you are charging off your own solar PV.

C: Your EV or portable charger has the capacity for timed charging, so you can set and forget the charge when you arrive home … and not need to get out of bed to switch on the charger at the start of the night off-peak period. (This avoids charging at peak cost/grid stress periods, like on a hot summer afternoon when the grid may be struggling under local air-conditioning loads).

If you do choose Mode 2 or standard power point charging as your home charging method: I would urge you to buy a second charger to use at home and leave the charger that came with the car in the boot.

In fact, I recommend treating the car’s charger in the same way as you do a spare tyre (if you are one of the lucky few to have a late model car with a spare tyre) and only use it for emergencies.

Otherwise Murphy’s Law will prevail and the one day you leave the portable charger from the car at home …. it will be the day you want to do an emergency top-up somewhere when you’re out and about!

However, you should install a Mode 3 charger if you:

This advice is tempered by the fact that there are no true ‘smart’ Mode 3 chargers yet. By ‘smart’, I mean ones that can be controlled by the grid to turn on/off or ramp the charging speed up or down depending on grid under or over supply conditions.

There are also no vehicle to grid (V2G) options yet (For an explanation of V2G options – click here). Chargers with both of these functions will likely become available in Australia around 2026 – although the first EVs capable of V2G should be available here within the next 12 months.

There are some ‘smart-ish’ Mode 3 chargers on the market now. These are the ones I referred to earlier regarding sensing the total load on the house to temporarily reduce EV charging to avoid overloading your home’s supply, as well as ones that can sense your solar PV output to maximise your solar EV charging.

Also, as briefly mentioned at the start – there is a third option of buying a higher power Mode 2 portable charger and installing a bigger outlet to suit.

This will give you some (or even all) of the shorter charging times that Mode 3 chargers offer, but it won’t give you the control that many Mode 3 chargers can do as a Mode 2 charger will never be ‘smart’, nor will it eliminate the need to plug it in and later put it away if it is in a location where it can be stolen from.

For low-use EV owners with power points wired properly to be EV charging outlets, Mode 2 is fine – but it has its limitations. Mode 3 is the choice for higher power EV users, as well as a generally more convenient charging experience – especially if you live in an all-electric household and/or have solar PV.

Iif you want the option to have a true smart charger that does V2G and smart grid control options (and don’t yet need solar and/or charge speed control in an all-electric house) perhaps wire the EV charging point as for a Mode 3 charger (including a data cable back to the switchboard), but install a 15, 20 or even 32A outlet on it and buy a higher power portable charger.

That way you can wait for the V2G charger whilst getting:

Bryce Gaton is an expert on electric vehicles and contributor for The Driven and Renew Economy. He has been working in the EV sector since 2008 and is currently working as EV electrical safety trainer/supervisor for the University of Melbourne. He also provides support for the EV Transition to business, government and the public through his EV Transition consultancy EVchoice.