A cost-per-distance table is one of the most useful buying tools, but only if every figure has the same distance unit and explicitly records the energy source. For 2020–2026 cars, blending EPA mpg, WLTP litres per 100 km and Brazilian labels without explanation can manufacture false savings.
Set a transparent common distance
For liquid fuel rated in L/100 km, multiply the labelled quantity by the local price per litre. For EVs rated in kWh/100 km, multiply electric energy purchased by the applicable tariff, adjusting for charging losses if the rating excludes them. If starting from US miles per gallon, make a transparent unit conversion but do not claim that converting the unit also converts EPA testing into WLTP.
Put pricing and charging context beside the result
An EV may use home electricity on weekdays but more expensive public DC energy on a holiday; a PHEV uses both electricity and liquid fuel in proportions shaped by charging frequency. Build at least two scenarios rather than a single falsely precise figure. Keep tax, insurance, financing, tyre replacement and depreciation outside the energy line so the reader does not mistake energy cost for total ownership cost.
Separate certification and observation
Official labels enable within-method comparisons; weather, traffic, driving style and battery age can shift actual results. European Commission monitoring has shown a material gap between lab and observed real-world fuel consumption for a historical vehicle cohort. That fleet statistic is not a mandatory correction factor for a specific 2025 car.
Keep the units visible at every stage
A chart can silently mix U.S. gallons, imperial gallons, kilometres and miles; this is a major source of incorrect comparisons. State the gallon definition and the lab cycle before converting distance units. For a flex-fuel car in Brazil, a petrol-based number and an ethanol number must be treated as separate operating modes. Publish a range of user-editable scenarios when tariffs vary by time of day.
Who should choose it?
The credible outcome is a reproducible calculator with inputs the buyer can change. Never label the lowest estimated energy cost as the lowest total-cost vehicle without the rest of the budget.
Model-year and market scope
Applicable to 2020–2026 powertrains, without invented fuel tariffs, FX rates, purchase prices or road-test results.