What is a good EV efficiency figure?

Most EVs achieve 3–4 miles per kWh in mixed driving. Smaller EVs like the Nissan Leaf achieve around 3.5 mpkWh; larger EVs like the Tesla Model 3 achieve around 4 mpkWh.

How does driving style affect the running cost comparison between electric and petrol cars?

Driving style can shift energy consumption by 20–30% relative to manufacturers' claimed figures. EVs are highly efficient in stop-start urban driving, where regenerative braking recovers energy that a petrol engine wastes as heat. At sustained motorway speeds above 70mph, EV efficiency drops noticeably, narrowing the running cost gap. When using the electric vs petrol calculator, enter real-world efficiency figures from owner reviews or sites like Spritmonitor rather than official manufacturer data for a more accurate comparison.

Electric vs Petrol Calculator UK

Useful next calculations

Use the Fuel Cost CalculatorContinue with the related car & transport question this result raises.
Use the Car Running Cost CalculatorContinue with the related car & transport question this result raises.

Rates and sources

DVLA, HMRC fuel advisory rates and manufacturer-published figures. Real-world results vary by driving style.

Source: DVLA / HMRC fuel advisory rates. Check the linked guidance and any live quote before acting.

When to use this calculator

When you need a fast estimate before making a bigger decision.
When you want to compare a few scenarios using the same assumptions.
When you need a clearer starting point before using a detailed quote or formal document.
When you want to sanity-check a figure you have seen elsewhere.

A worked example

These are the example figures the calculator opens with.

A worked example
Input	Value
Annual Miles	10,000
Petrol Car MPG	40
Petrol Price Per Litre (£)	£1.52
EV Miles Per kWh	3.5

For those figures the calculator returns:

Petrol annual cost: £1,727.51
EV annual cost: £685.71
Annual saving: £1,041.80

How to read your results

Annual Saving

The recurring yearly benefit of the change or upgrade under the assumptions you entered.

Method & assumptions

This calculator compares the estimated annual running costs of an electric vehicle against a petrol equivalent based on your annual mileage, home electricity rate, petrol price, and the efficiency figures for each vehicle. EV efficiency is expressed in miles per kWh; petrol efficiency in MPG. The comparison covers fuel or energy costs only — it does not include purchase price differences, depreciation, insurance, or servicing, all of which vary significantly by model and driver profile. Public charging costs are not factored into the default calculation; if you rely on public chargers for a portion of your charging, adjust the electricity rate upward accordingly to reflect your blended cost per kWh.

Common mistakes

Using optimistic assumptions without testing a more cautious scenario.
Comparing outputs from different tools without checking that the inputs match.
Treating the result as a final quote instead of a planning estimate.
Rounding inputs too aggressively.

What to do next

Try at least one more scenario so you can compare a realistic range.
Use the related calculators below to cross-check the decision from another angle.
Write down the key outputs from your best scenarios before you decide.
If the result surprises you, change one input at a time to isolate the driver.

Questions people ask

Yes — at typical UK home electricity rates, EV running costs are 3–4x lower per mile than petrol. The saving depends heavily on whether you charge at home or use public chargers.