Energy consumption and cost per km

EV efficiency is measured in kilowatt-hours per 100 km (kWh/100km). A typical EV uses 15–20 kWh/100km. The cost per km is:

Cost per km = (kWh/100km ÷ 100) × blended electricity rate (c/kWh)

Compare this to a petrol car: at 8L/100km and $2.00/L, fuel costs 16c/km. An EV using 17 kWh/100km at a home rate of 28c/kWh costs 4.76c/km — about 70% cheaper.

Charging mix: home, public, and solar

Most EV owners charge primarily at home overnight, where electricity rates are lowest. Public DC fast charging is significantly more expensive (60–90c/kWh at commercial networks). Solar charging is treated as near-zero marginal cost.

The blended rate = (home% × home rate) + (public% × public rate) + (solar% × $0). The percentages must sum to 100%.

Key metrics explained

• Cost per km: Your average charging cost for each kilometre driven.
• Monthly charging cost: Annual km ÷ 12 × cost per km.
• Annual charging cost: Annual km × cost per km.
• Equivalent petrol cost: What you'd spend fuelling a petrol car at the same distance, for comparison.

Worked example

Vehicle: 17.5 kWh/100km. Annual km: 15,000. Charging mix: 80% home at 28c/kWh, 15% public at 75c/kWh, 5% solar.

• Blended rate: (0.8 × 28) + (0.15 × 75) + (0.05 × 0) = 22.4 + 11.25 = 33.65c/kWh
• Cost per km: 17.5 ÷ 100 × $0.3365 = 5.89c/km
• Annual cost: 15,000 × $0.0589 = $883
• Equivalent petrol car (8L/100km at $2.00/L): $2,400/year — saving $1,517

Home electricity rate

The default home rate is the average residential flat rate for your state, sourced from AER data. Many EV owners benefit from time-of-use tariffs that offer lower overnight rates (e.g. 10–18c/kWh overnight vs 25–35c/kWh during the day). Enter your actual off-peak rate for a more accurate estimate.

Electricity rates are sourced from AER published data and may not reflect your specific tariff. Results are estimates only. Not financial advice.