Use the same distance
An energy comparison only makes sense when both vehicles cover the same distance. Suppose each travels 15,000 km a year. An EV using 18 grid kWh per 100 km consumes 2,700 kWh. At 0.20 per kWh, annual electricity spending is 540. A gasoline vehicle using 8 litres per 100 km consumes 1,200 litres. At 1.50 per litre, annual fuel spending is 1,800.
Under those entered assumptions, the difference is 1,260 a year. This is an original scenario calculation, not a forecast of fuel prices or a claim about a particular vehicle.
Include the electricity drawn from the grid
Battery energy and grid energy are not identical when charging has losses. If your consumption figure already includes grid losses, do not apply them again. If you only know battery capacity and the percentage you plan to add, use the charging calculator with an explicit charging-efficiency assumption.
Public rapid charging and home charging can have different prices. You can calculate each portion of annual energy separately and add the costs. A blended price is only useful if it reflects the actual share charged at each rate.
Energy savings are not total savings
The EV comparison excludes purchase price, financing, insurance, depreciation, maintenance and charger installation. A vehicle with lower energy cost may still have a higher total ownership cost. Use the ownership worksheet to include those items before comparing the overall budget.
Keep annual distance and the ownership period consistent across both tools. Otherwise, the same scenario may appear better or worse simply because different time periods were used.