RealCost Tool
Electric vs Petrol Running Cost Calculator
Electric cars can be cheaper per mile than petrol cars, but the real saving depends on petrol price, MPG, electricity price, EV efficiency and how many miles you drive.
Use this calculator to compare petrol and electric running costs side by side, including cost per mile, cost per 100 miles, yearly cost and estimated monthly or annual savings.
Compare petrol cost
Estimate petrol cost per mile, per 100 miles and per year using fuel price and MPG.
Compare electric cost
Estimate EV charging cost per mile, per 100 miles and per year using kWh price and efficiency.
See possible savings
Work out whether electric could be cheaper for your yearly mileage.
Compare electric and petrol running costs
Enter petrol price, petrol MPG, electricity price, EV efficiency and yearly mileage to compare petrol and electric energy costs.
This calculator compares fuel and charging running costs only. It does not include purchase price, finance, insurance, road tax, depreciation, tyres, servicing or charger installation.
Cheaper per mile does not always mean cheaper overall
Electric may cost less to run per mile, especially with cheaper home charging. But the full decision should also include purchase price, finance, insurance, depreciation, tyres, maintenance, road tax and charging access.
RealCost note: Use this calculator for the energy-cost comparison. Then use the Car Cost Calculator UK before deciding which car is actually cheaper to own.
What the calculator includes
The calculator compares petrol and electric energy costs using five simple inputs.
Petrol price per litre
Enter the petrol price you expect to pay per litre.
Petrol car MPG
Enter the petrol car’s miles per gallon. Use a realistic real-world MPG figure if possible.
Electricity price per kWh
Enter the electricity price you expect to pay when charging the EV.
EV efficiency
Enter the electric car’s miles per kWh. Higher miles per kWh usually means lower charging cost per mile.
Miles driven per year
Enter your expected yearly mileage so the calculator can estimate annual costs and savings.
Estimated saving
The results show whether electric is cheaper than petrol based on the numbers entered.
What the results tell you
The results compare petrol and electric running cost in everyday formats.
Petrol cost per mile
Estimated petrol cost for each mile driven.
Electric cost per mile
Estimated electricity cost for each mile driven.
Cost per 100 miles
A simple way to compare both vehicles over the same distance.
Estimated yearly costs
Estimated annual petrol and electric running costs based on your mileage.
Estimated annual saving
How much electric could save over a year if it is cheaper than petrol.
Estimated monthly saving
The annual saving divided into a monthly figure for easier budgeting.
Example electric vs petrol result
This example uses £1.50 petrol, 45 MPG, £0.25/kWh electricity, 3.5 miles per kWh and 10,000 miles per year.
Petrol cost per mile
£0.15
Electric cost per mile
£0.07
Petrol yearly cost
£1,515.33
Electric yearly cost
£714.29
Estimated electric saving:
about £801 per year
That saving only covers energy cost. It does not prove the EV is cheaper overall once purchase price, insurance and depreciation are included.
Home charging vs public charging
Charging price can completely change the EV result, so run separate estimates if you use more than one charging type.
Home charging may suit you if
- You have off-street parking
- You can charge overnight
- You drive regular weekly mileage
- You can access a suitable electricity tariff
Public charging needs more care if
- You cannot charge at home
- You rely on rapid chargers
- You do frequent long trips
- Charging prices vary on your route
Important: The calculator uses one electricity price at a time. If you charge partly at home, partly at work and partly on public chargers, run separate estimates using different pence-per-kWh values so the saving does not look too optimistic.
Next step: For charging-specific estimates, use the EV Charging Cost Calculator UK.
When electric wins and when petrol still makes sense
The best choice depends on charging access, mileage, purchase price and how you use the car.
Electric may suit you if
- You can charge conveniently
- You drive regular mileage
- Your trips fit the car’s range
- You can get a sensible purchase price
- You have checked insurance and depreciation
Petrol may suit you if
- You do low mileage
- You cannot charge easily
- You need a cheaper car upfront
- You make unpredictable long journeys
- You want simple refuelling access
What changes the result?
Small changes in energy price, efficiency or mileage can make a big difference over a year.
Higher mileage usually makes cost-per-mile differences more important.
Home, workplace, destination and rapid public charging can have very different prices.
A very efficient petrol car can narrow the running-cost gap.
A more efficient EV can reduce the cost per mile significantly.
Speed, acceleration, braking and journey type affect both petrol MPG and EV efficiency.
Large, heavy or performance cars usually cost more to run in either fuel type.
When this calculator is most useful
Use it when you want to compare energy running costs before making a car decision.
What to calculate next
Use these calculators to turn the running-cost result into a stronger buying decision.
EV Charging Cost Calculator UK
Estimate EV charging cost per charge, per mile and per year.
Fuel Cost Per Mile Calculator UK
Work out petrol or diesel cost per mile, per month and per year.
Car Depreciation Calculator UK
Check whether value loss changes the total cost picture.
Car Insurance Cost Calculator UK
Compare insurance quotes because they can change the electric vs petrol saving picture.
Car Maintenance Cost Calculator UK
Add servicing, MOT, tyres and repair allowance into the ownership comparison.
Commute Calculator UK
Compare petrol or EV running cost against your actual work travel.
Related electric, petrol and hybrid guides
Use these guides when the calculator result raises a wider car-buying question.
Cheapest Hybrid Cars to Run UK
Compare efficient hybrid options if full electric is not right.