In short
The plan that prices the hours you charge in cheapest, on your whole usage, not just the car's. An electric car adds a large, movable load, so an overnight charger suits a time-of-use plan with a low off-peak rate, a daytime charger with solar suits self-consumption or the Solar Sharer window, and a car charged in the evening peak makes almost any time-of-use plan dearer than a single rate. It needs a smart meter, and it is worth a fresh comparison the month the car arrives.
What a car does to the bill
A typical electric car driven an ordinary amount adds a load comparable to a second household's worth of electricity, and unlike the air-conditioner it can run whenever you tell it to. That makes it the load that decides which tariff wins, and the reason the answer for a home with a car can be the opposite of the answer for the same home without one.
Match the tariff to when you charge
| Overnight, from a wall charger | A time-of-use plan with a low off-peak rate, or an EV-specific plan with a cheap overnight window. Set the charger to start after the peak ends. |
|---|---|
| Daytime, at home, with solar | Self-consumption first: charging from your own panels costs you only the feed-in credit forgone. A Solar Sharer plan can suit a car that charges between 11am and 2pm; the 24 kWh daily cap is one of the few cases where it binds. See the Solar Sharer Offer explained. |
| Whenever you get home, in the evening | A single-rate plan. Charging in the peak on a time-of-use plan is the dearest electricity on the market, and a demand plan will record the charger as your peak every month. |
| Mostly away from home | The car barely changes the answer; compare on the house alone. |
Things to check
- Eligibility. Some EV plans require a particular charger or a controlled-load circuit for it. Read the conditions.
- The peak. A cheap overnight window is only cheap if the charger is set to use it; an evening top-up on the same plan is charged at the peak rate.
- Demand. On a demand tariff a seven-kilowatt charger sets a high peak whenever it runs in the window. Charge outside it or avoid the tariff.
- Your meter. Time-of-use and EV plans need a smart meter; see do I need a smart meter.
The comparison worth doing is on your usage with the car in it, half hour by half hour: a meter-data file from your retailer's portal after a month or two of charging shows exactly where the load lands, and the paid check prices every plan on it, including the shift to overnight if you can make it.
Quick answers
Is a time-of-use plan good for charging an electric car?
Yes, if the car charges overnight in the off-peak window and no, if it charges in the evening peak. The car is a large, movable load, so a scheduled overnight charge on a low off-peak rate is one of the best uses of a time-of-use plan, while an evening charge on the same plan is the dearest electricity on the market.
Should I charge my electric car from solar or from the grid overnight?
From solar during the day if the car is home, because self-consumed solar costs you only the feed-in credit you would have earned, which is less than any grid rate. Overnight on an off-peak rate is the next best thing. The worst case is the evening peak on a time-of-use or demand plan.
Sources
Official pages this answer relies on. If one of them changes, tell us and we will update the page.
- Solar Sharer Offer · Australian Government, energy.gov.au
- Residential electricity tariffs · Energex
- Energy Made Easy · Australian Energy Regulator