Most EV cost questions end up as one number: what does a charge actually cost. But the number that matters for a car you own every day is cost per 100 km, because that is the unit that lets you compare two cars, two tariffs and two driving patterns.

What you need

Three inputs, all of which you can get without any special equipment:

• Your electricity price, in cents per kWh. Most Australian retailers publish a single default tariff; time-of-use tariffs publish different rates by period.
• Your usable battery capacity in kWh. Use the usable figure, not the headline number, because most cars reserve some capacity.
• Your real-world consumption in kWh per 100 km, if you have it, or the official test figure as a starting point.

The calculation

Energy in is consumption divided by 100, adjusted upward for charging loss, then multiplied by your price per kWh. Put plainly:

cost per 100 km = (consumption / 100) / (1 - loss) * price per kWh

The loss term is the part most people skip. Energy that goes into the charger and the car does not arrive at the battery. Treat it as an explicit planning assumption rather than a hidden constant, because the calculator on this site states the loss rate it used and you can change it.

Why the same tariff gives different answers

Two cars on the same tariff can differ substantially, and the reason is usually one of three:

• Battery size. A larger pack spread over the same distance needs fewer kWh per 100 km.
• Efficiency. Consumption is not a fixed property of the car; it depends on speed, temperature and load.
• Charging losses. These vary with temperature and with how fast you charge. Slow charging is generally more efficient than rapid charging.

Using the calculator

The cost calculator takes your usable battery, current and target charge, charging power and price, and shows the cost of that charge along with the assumptions it used. Enter your own numbers rather than a rounded example, because the whole point is that the result has to be defensible for your own car and tariff.

What this does not tell you

These are planning estimates. They do not include connection fees, subscription discounts, export credits, or any off-peak tariff you may qualify for but have not applied for. They are not a billing calculation and not financial advice. If you need a number that matches an actual invoice, use the invoice.