EV Charging Cost vs Petrol
Reviewed by Edward, publisher and site editor ·
Comparing an EV with a petrol car requires both vehicles to be converted to the same cost-per-distance metric. For the EV, combine electricity consumption, charging efficiency and electricity price. For the petrol car, combine fuel consumption and petrol price.
The result can change dramatically depending on where the EV is charged. Cheap home electricity often produces a strong running-cost advantage, while frequent premium rapid charging can reduce or even remove that advantage for some vehicles and fuel prices.
EV cost per 100 km
Start with the vehicle's energy consumption in kWh per 100 km. Divide by charging efficiency to estimate wall energy, then multiply by the electricity price per kWh. A car using 17 kWh per 100 km at 90 percent charging efficiency draws about 18.9 kWh from the wall per 100 km.
At 0.20 per kWh that is about 3.78 per 100 km. At 0.65 per kWh on a rapid charger the same vehicle costs about 12.28 per 100 km. The efficiency of the car has not changed; the energy source has.
Petrol cost per 100 km
For a petrol car, multiply litres used per 100 km by the pump price per litre. A car consuming 6.5 L/100 km at 1.70 per litre costs 11.05 per 100 km in fuel. A less efficient 8.0 L/100 km vehicle at the same pump price costs 13.60 per 100 km.
This comparison covers energy or fuel only. It does not include purchase price, depreciation, insurance, servicing, road tax, tyres or financing, which can be more important than energy cost in total ownership calculations.
Why home charging changes the result
Home charging often allows the EV to buy energy at a residential or off-peak tariff instead of a commercial rapid-charging rate. Because the vehicle's kWh-per-distance consumption is unchanged, every reduction in the electricity price directly reduces running cost per kilometre.
A driver who can move charging into a low-cost overnight window may therefore see a much larger saving than a driver with the same car who relies on public rapid charging for most energy.
Break-even electricity price
The break-even electricity price is the per-kWh rate at which EV energy cost equals the petrol car's fuel cost per distance. It can be estimated by dividing the petrol cost per 100 km by the EV wall-energy consumption per 100 km.
Using the example above, a petrol cost of 11.05 per 100 km divided by 18.9 kWh of EV wall energy gives a break-even electricity price of roughly 0.58 per kWh. Below that rate the EV is cheaper on energy; above it the petrol car is cheaper on fuel for those exact assumptions.
Use real consumption, not brochure best cases
Both EV and petrol consumption vary with speed, temperature, terrain, tyres and driving style. Comparing an optimistic laboratory EV figure against a real petrol average, or the reverse, biases the result. Use real mixed-driving consumption for both vehicles where possible.
For EVs, winter heating and motorway speeds can materially increase kWh per 100 km. Petrol cars also consume more in cold weather and at high speed. A fair comparison should use data from similar routes and conditions.
What this comparison does not include
Energy cost is only one part of ownership. Maintenance schedules, tyres, insurance, taxes, depreciation, home-charger installation and finance can outweigh small differences in fuel or electricity. This guide isolates energy cost so that one variable is understood clearly before total ownership is considered.
It also excludes the value of charging time and convenience. Home charging may save trips to a fuel station, while long-distance DC charging may add planned stops. Those factors are real but are difficult to express as one universal monetary value.
Common questions
Are EVs always cheaper per mile than petrol cars?
No. The result depends on EV efficiency, charging losses, electricity price, petrol-car efficiency and petrol price.
Why does public rapid charging reduce EV savings?
Rapid-charging electricity is commonly much more expensive per kWh than residential electricity.
Should purchase price be included in this comparison?
Not in an energy-cost comparison. Purchase price belongs in a broader total-cost-of-ownership calculation.