Decide what cost you are comparing
There are three different questions: cash needed to buy the car, running cost after purchase, and economic cost over the ownership period. A lower energy bill answers only one of them. Set the same period and annual distance for both vehicles before comparing totals.
EVVerity’s EV-versus-petrol tool adds purchase price, energy, service and insurance. Its total excludes resale, finance, taxes, tyres and other costs shown in the separate Cost of Ownership tool. Read that boundary before calling the result a complete ownership comparison.
Work through one set of explicit assumptions
This fictional comparison uses pounds, 12,000 km per year and constant prices. The EV costs £18,000, uses 18 kWh/100 km and buys electricity at £0.25/kWh with a 10% grid-loss assumption. The petrol car costs £15,000, uses 6.5 litres/100 km and buys fuel at £1.50/litre. Service is £300 versus £450 per year; insurance is £700 versus £600. These are teaching inputs, not current quotes.
The EV buys 2,400 kWh annually, costing £600. The petrol car uses 780 litres, costing £1,170. Add the stated service and insurance amounts before comparing the saving.
| Annual item | EV | Petrol |
|---|---|---|
| Energy | £600 | £1,170 |
| Service | £300 | £450 |
| Insurance | £700 | £600 |
| Included running costs | £1,600 | £2,220 |
Understand the break-even result
The EV’s purchase premium is £3,000 and its included running-cost saving is £620 per year. The simple break-even is £3,000 ÷ £620, or about 4.84 years. Over five years, purchase plus included running costs total £26,000 for the EV and £26,100 for the petrol car.
That £100 difference is small compared with several excluded costs. It would be misleading to describe this scenario as a decisive saving. Obtain the missing quotes and examine resale and finance assumptions before relying on the comparison.
Change the charging routine, then the annual distance
At £0.65/kWh public charging with everything else unchanged, annual EV energy costs become £1,560 and its included running costs become £2,560. The EV then costs £340 more per year within this model, as well as £3,000 more to buy. There is no positive recovery of that purchase premium under those inputs.
Alternatively, keep the £0.25 tariff but reduce driving to 6,000 km/year. The energy saving halves to £285 while the net service and insurance advantage remains £50. The resulting £335 annual saving takes about 8.96 years to recover the premium. This shows why the same two cars can produce different answers for different households.
Bring resale and finance back into the decision
For economic ownership cost, subtract your assumed resale value from purchase price and add interest and operating expenses. Do not add the full purchase price again after including depreciation. Loan repayments include principal, so a monthly cash payment is not interchangeable with a monthly economic cost.
Try more than one resale outcome and use real insurance and finance quotes. A higher deposit changes cash flow and borrowing, but it does not eliminate depreciation. Keep any incentive or tax assumption tied to the actual country, eligibility and period instead of copying it from another market.
Use the result to identify the next piece of evidence
If charging access drives the outcome, confirm your likely home/public mix. If a small insurance difference changes the ranking, obtain both quotes before spending more time refining the energy calculation. If resale dominates, show a range of outcomes rather than treating one estimate as a valuation.
A useful comparison explains what must be true for one option to cost less. It also leaves space for practical differences such as charging time, luggage space and the condition of the specific cars. The calculator organises the cost assumptions; it does not issue a purchase verdict.
Put the explanation to work
Use your own vehicle information, check the assumptions and see the calculation.
EV vs Gas / Petrol →EVVerity estimates are informational and are not a substitute for a professional battery diagnostic or pre-purchase vehicle inspection.
Sources & editorial basis
- US Department of Energy — AC charging and the onboard charger
- US Department of Energy — driving conditions and electric range
Source list reviewed 2026-10-26. Additional guidance carries its own review date. Practical checklists and worked examples are EVVerity editorial guidance. Read our methodology.
Related reading
Apply this to a model
Check the model’s battery references, charging equipment and viewing checklist. Match the year and original market to the car you are considering.