Check your charging speed

Before deciding when to charge first check on how long you will need to be charging your EV for.

There are three common charging speeds, 2.3 kW chargers that connect to a regular wall outlet, 7 kW fast wall chargers, and high power 3 phase chargers at 11 kW or more.

At 7 kW or faster, most drivers will only need a couple of hours of charging each day, and will be quite flexible in what time of day they charge and you can maximise how much you can charge from rooftop solar. If you're charging from a regular wall outlet and driving above average kilometres you might need some longer charging sessions with less flexibility on starting times.

For more details see our article on home EV charging speeds.

Rooftop solar

If you have rooftop solar and your EV is often home during the day, in most cases it will be the cheapest and greenest energy you can get. Charge HQ can help you automate this.

Get the best energy plan

Once you've ticked off charging from your rooftop solar the next step is to consider the energy plan you're on with your electricity retailer.

1. Review your tariff type: if you're on a flat rate tariff, consider if switching to a time of use tariff (or vice versa) can reduce your bill. Wattever's guide on tariff switching provides some great advice on working out which is the best option.
2. Review your retail electricity plan: after buying an EV your electricity bill will increase since it now includes the energy you would have previously purchased in the form of petrol (although it will almost certainly cost less than the petrol did!). Getting the right plan from your retailer becomes even more important. Wattever can help you find the best electricity plan for use with an EV.

Charge at the lowest price

If your priority is to minimise your charging cost the best time depends on your tariff type:

• On Flat Rate / Anytime: your charging cost remains the same regardless of what time of day you charge.
• Time of Use: The cheapest power is during the off-peak periods, in most locations this will be overnight often between 10pm and 7am. In South Australia and parts of Queensland it's during the middle of the day. Check your energy bill for details.
• Variable rate: It's a bit more complex but you'll find some suggestions in our guide for using Charge HQ with Amber Electric.

If you are on flat rate, you should still avoid charging during the early evening which is often a peak demand period, in the long run you'll pay more for power if a lot of EV drivers do this.

Charge from the most renewables

As discussed in our article on factors to consider when to charge your EV, charging during periods of high renewables helps reduce emissions from electricity generation and in the long term should help bring down power prices.

Periods of high renewables change on a daily and seasonal basis, and the relative levels vary significantly across different Australian states. Ideally EV charing times will be automatically controlled and scheduled on a daily or even hourly basis to align with periods of maximum renewable generation. This is where we're headed with Charge HQ but for now some charging still needs to operate on a regular schedule.

If you want to schedule charging from the most renewables:

For Queensland, New South Wales & Victoria:

• If you can, charge during the middle of the day when solar output is most often high. For 2 hours, use 11am to 1pm, 4 hours: 10am - 2pm.
• If you have to charge over night, from 10pm onwards (so you avoid peak loads and tariffs), average renewable contribution is relatively flat. Any time between 10pm and 6am is about the same.

For South Australia:

• If you can, charge during the middle of the day when solar output is most often high. For 2 hours, use 11am to 1pm, For 3 hours, use 11am - 2pm, 4 hours: 10am - 2pm.
• If you have to charge over night, on average there's a material increase in wind generation between 2am and 5am. If you need more than 3 hours overnight you can push this out to 1am to 6am.

For Tasmania:

• The majority of energy is already generated by renewable hydro power, so time of day has less impact.
• If you want to support continued solar development, try and charge during the middle of the day as much as possible.
• For overnight charging - prioritise early hours of the morning to avoid peak load periods.

The recommended times are derived by considering share of generation from renewable energy as published by NEMlog.

OpenNem also had a time of day view, showing the renewables contribution to grid supplied energy by time of day, averaged over the last month.

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