THE METHOD · 22 OCTOBER 2026
Show the working.
Your estimate is the electricity needed for your distance, multiplied by the rate you pay. Solar is valued at the export income you give up.
1. Energy for your weekly drive
kWh/week = Wh/km ÷ 1,000 × km/week × (1 + extra allowance ÷ 100)
The default energy figures are certified figures from the Australian Government’s Green Vehicle Guide or the linked Australian manufacturer. Each configuration keeps its release year and direct source. They are a comparison baseline. Weather, speed, terrain and air conditioning can change your use.
We do not apply a blanket charging-loss uplift: a certified energy figure’s measurement boundary must be checked first to avoid counting losses twice. The optional extra allowance starts at zero and is your adjustment, not a measured charging efficiency claim.
2. Home and solar
Home effective rate = home rate × (1 − solar share) + feed-in tariff × solar share
Shares in this formula are fractions from 0 to 1. Only surplus solar that would otherwise be exported is valued at the feed-in tariff. Solar already needed by your home, or stored in a battery, needs a different opportunity-cost assumption. The example 5c/kWh feed-in tariff is an editable scenario.
3. Public and mixed charging
Blended rate = home effective rate × (1 − public share) + public rate × public share
EV cost/week = energy/week × blended cents/kWh ÷ 100 + public fees/week
Public fees are included only when you drive and use public charging. The 65c/kWh example is a scenario, not a verified network price. The calculator uses the same certified energy baseline across charging modes. It is an energy-cost scenario, not a prediction of the exact AC or DC energy billed at a charger. Use your measured Wh/km and appropriate extra allowance to refine it.
4. Petrol comparison
Petrol cost/week = km/week × L/100 km ÷ 100 × petrol cents/litre ÷ 100
Saving/week = petrol cost/week − EV cost/week
7.5 L/100 km and 205c/litre are example inputs, not current market averages. A negative saving means electricity costs more at your rates. This is an energy-cost comparison, not total ownership cost.
5. Electricity defaults
NSW, south-east Queensland and South Australia use the AER’s 2026–27 residential flat-rate tariff caps. Victoria uses the ESC’s 2026–27 domestic flat tariffs. WA, Tasmania, the ACT, the NT and regional Queensland use the linked published residential reference tariff. Meter, connection and usage restrictions are shown in the source register and rate note. Rates include GST and are selected by distribution zone. They are reference defaults, not a claim about your plan or the cheapest available offer.
The daily supply charge is excluded because an existing household connection already pays it. Switching plans can alter that charge and other household rates, so an EV-only saving does not establish that a plan is cheaper overall.
6. Rounding and scope
We keep full precision until display. Weekly dollars display to the nearest cent; cents per kilometre display to one decimal. The annual example uses 52 identical weeks. Zero kilometres returns zero variable cost. Purchase, finance, tax, maintenance, insurance and charger installation are excluded.