Show the workings.
Daily battery energy = vehicles × daily km × kWh/100 km ÷ 100.
Daily grid energy = battery energy ÷ (efficiency ÷ 100).
Average charging power = grid energy ÷ charging hours.
Annual electricity cost = daily grid energy × operating days × tariff.
Annual diesel cost = vehicles × daily km × L/100 km ÷ 100 × days × fuel price.
Energy cost difference = diesel cost − electricity cost.