EV vs petrol cost comparison calculator UK
Compare petrol fuel costs with EV charging costs using your annual mileage, petrol price, fuel economy, electricity rate and EV efficiency.
How the EV vs petrol calculator works
The calculator compares the energy cost of driving the same annual mileage in a petrol car and an electric car.
4.54609 litres per UK imperial gallon ÷ mpg
Petrol cost per mile:
Litres per mile × petrol price per litre
EV battery energy per mile:
1 ÷ EV miles per kWh
Grid electricity per mile:
Battery energy per mile ÷ charging efficiency
EV charging cost per mile:
Grid electricity per mile × electricity unit rate
Annual cost:
Cost per mile × annual mileage
Worked example
An EV achieving 3.8 miles/kWh, with 90% charging efficiency and electricity at 26.11p/kWh, uses approximately 0.292 kWh of grid electricity per mile.
That produces an estimated charging cost of approximately £763 per year.
The difference in energy costs is therefore approximately £1,420 per year in this example.
Current UK benchmark figures
The default petrol price is currently 168.14p per litre, the Department for Energy Security and Net Zero average UK unleaded petrol pump price for the week commencing 14 September 2026.
The default electricity rate is 26.11p/kWh, the Ofgem average electricity unit rate for a standard variable tariff paid by Direct Debit in Great Britain for 1 July to 30 September 2026.
EV efficiency and charging losses
EV efficiency in this calculator is entered in miles per kWh. A higher figure means the vehicle travels farther for each unit of battery energy.
The calculator then applies the charging-efficiency setting to allow for electricity lost between the supply and the energy stored in the battery.
For example, an EV achieving 3.8 miles/kWh at the battery and charging at 90% efficiency requires approximately 0.292 kWh of electricity from the supply for each mile driven.
What the comparison does not include
This is an energy-cost comparison rather than a total-cost-of-ownership calculator.
It does not include vehicle purchase price, depreciation, finance, insurance, Vehicle Excise Duty, servicing, repairs, tyres, parking, charger installation costs or other ownership expenses.
It also assumes the annual mileage entered is the same for both vehicles.
Alternative EV rate
The alternative rate applies the same EV efficiency, charging losses and mileage to another electricity price.
It can be used to compare a standard home rate with an off-peak EV tariff, but it assumes all of the EV’s charging electricity can be purchased at that rate.
How much cheaper is an electric car than petrol in the UK?
The answer depends on the petrol car’s fuel economy, petrol price, EV efficiency, charging losses and the electricity rate used to charge the EV. The calculator above lets you change each of those assumptions rather than relying on one fixed national example.
For comparison, the official UK average unleaded petrol price for the week commencing 31 August 2026 was 161.61p per litre. The Ofgem average electricity unit rate for a standard-variable Direct Debit tariff in England, Scotland and Wales is 26.11p/kWh for July to September 2026. Your own prices may be different.
An EV averaging 3.8 miles/kWh and charging at 90% efficiency uses about 0.292 kWh of grid electricity per mile. At 26.11p/kWh, 10,000 miles costs about £763 in charging electricity — a difference of about £1,336 per year in fuel and charging energy alone.
Example EV vs petrol energy costs
| Scenario | Cost per mile | Annual cost | Difference vs petrol |
|---|---|---|---|
| Petrol — 35 mpg at 161.61p/litre | ~21.0p | ~£2,099 | — |
| EV — 26.11p/kWh | ~7.6p | ~£763 | ~£1,336 less |
| EV — 15p/kWh | ~4.4p | ~£439 | ~£1,661 less |
| EV — 10p/kWh | ~2.9p | ~£292 | ~£1,807 less |
| EV — 8p/kWh | ~2.3p | ~£234 | ~£1,865 less |
Example assumes 10,000 miles per year, 35 mpg for the petrol car, 3.8 miles/kWh for the EV and 90% charging efficiency. The figures compare petrol and charging electricity only.
How is the petrol cost calculated?
UK fuel economy is normally quoted in imperial miles per gallon. One imperial gallon contains 4.54609 litres. The calculator converts the selected mpg figure into litres used per mile, then multiplies that by the petrol price entered.
How is the EV cost calculated?
EV efficiency is entered in miles per kWh. The calculator first estimates how much battery energy is required to travel each mile. It then adjusts that figure for charging losses before applying the electricity price.
For example, at 3.8 miles/kWh the battery uses about 0.263 kWh per mile. At 90% charging efficiency the electricity meter supplies about 0.292 kWh per mile. This is why grid electricity cost is slightly higher than a calculation based only on battery energy.
What about public charging?
You can use the calculator for public charging by entering the price you actually pay per kWh. If you use a mixture of home and public charging, entering a realistic blended average electricity rate will give a more representative result.
What about insurance, servicing and depreciation?
They are not included. This calculator deliberately compares petrol and charging electricity only. Purchase price, finance, depreciation, insurance, servicing, tyres, vehicle tax and other ownership costs can materially change the total cost of owning either vehicle.
How accurate is this calculator?
It is a scenario calculator rather than a prediction of your exact bills. Real-world fuel economy and EV efficiency vary with speed, temperature, journey type, driving style, tyres and vehicle condition. Charging efficiency also varies. For the best estimate, replace the default figures with values from your own driving, charging records and energy bills.
Frequently asked questions
How much does it cost to run an electric car per mile in the UK?
It depends on EV efficiency, charging losses and the electricity rate. As an example, an EV averaging 3.8 miles/kWh with 90% charging efficiency uses around 0.292 kWh of grid electricity per mile. At 26.11p/kWh that costs about 7.6p per mile. At 8p/kWh it costs about 2.3p per mile.
How much can an electric car save per year compared with petrol?
There is no single figure because it depends on mileage, petrol economy, petrol price, EV efficiency and charging price. Using the calculator’s default example of 10,000 miles, 35 mpg petrol, 161.61p/litre, 3.8 miles/kWh EV efficiency, 90% charging efficiency and electricity at 26.11p/kWh, the fuel and charging-energy difference is about £1,336 per year. Enter your own figures for a more relevant comparison.
Is it cheaper to drive an EV or a petrol car?
An EV can have a substantially lower energy cost per mile when charged at relatively low electricity rates, but that does not automatically mean the vehicle is cheaper to own overall. Purchase price, depreciation, finance, insurance, servicing, tax and other costs are outside this calculator and should also be considered.
Does the calculator include charging losses?
Yes. The calculator defaults to 90% charging efficiency. At that setting, an EV needing 1 kWh of energy stored in its battery is assumed to draw about 1.11 kWh from the electricity supply. You can change the efficiency assumption to 85%, 95% or an idealised 100%.
Can I include public charging costs?
Yes. Enter the electricity price you actually pay for charging. If you charge partly at home and partly on public networks, you can enter an estimated blended average rate. The home charging cost calculator is better suited to detailed home-charging scenarios.
How does petrol price affect the comparison?
For a 35 mpg petrol car travelling 10,000 miles per year, every 10p/litre change in petrol price changes annual fuel cost by about £130. The calculator lets you enter your own local petrol price so you do not have to rely on the national average.
What EV efficiency figure should I use?
If possible, use the long-term miles-per-kWh figure shown by your own vehicle rather than a manufacturer claim. Efficiency varies with vehicle, weather, speed, route and driving style. If you are considering an EV you do not yet own, the model presets provide an approximate starting point that you can adjust manually.
Does this calculator compare the total cost of ownership?
No. It compares petrol fuel cost with EV charging electricity cost. It does not include vehicle purchase price, finance, depreciation, insurance, servicing, repairs, tyres, tax, parking or other costs.