What Does the Vehicle A vs B Total Ownership Comparator Do?
The ownership comparator puts two cars on the same time horizon and combines energy, depreciation and recurring ownership costs. Its purpose is to reveal costs that an MPG comparison misses. You can see both period totals and annual components, and test whether a resale assumption changes the winner. The starting vehicles and prices are illustrative; the tool does not fetch valuations, insurance quotes or a personalised finance offer.
How to Use This Calculator
- Select a common ownership period. For each car, choose its energy type and enter mileage and the matching efficiency and price fields. Hidden fields for the other energy type are not part of that car's energy calculation.
- Enter current or purchase value and expected end value for the same future date. Check actual quotations where possible and run a less favourable resale case if the decision depends on a small difference.
- Complete the annual cost categories using comparable assumptions for both cars. Enter finance interest and fees, not full capital repayments on top of depreciation. Use your vehicle-specific tax charge rather than treating the starting example as a current statutory rate.
- Calculate and read period totals, component costs and resale sensitivity together. The equal-mileage crossover assumes fixed non-energy costs, so it is a model comparison rather than a forecast of how maintenance and resale change with mileage.
The Maths & Assumptions Behind the Tool
Annual depreciation = (current or purchase value − expected resale value) ÷ years. Annual ownership cost adds depreciation, energy and the entered recurring categories. Multiplying by years gives the modelled period total. A zero-mileage car can still have substantial fixed costs; its cost per mile is undefined. The model does not include the opportunity cost of tied-up capital unless you choose an explicit allowance, and it does not discount future cash flows.
Worked example
Use three years and 10,000 miles/year for both cars. Car A: 40 UK MPG, 145p/litre, £18,000 current value and £10,000 resale. Annual non-energy costs are £650 insurance + £200 tax + £550 servicing + £300 tyres + £55 MOT = £1,755.
Car B: 3.5 miles/kWh at the battery, 90% charging efficiency, 18p/kWh, £24,000 purchase value and £13,500 resale. Its annual non-energy costs are £800 insurance + £200 tax + £400 servicing + £350 tyres + £55 MOT = £1,805. Tax figures are example entries for both cars.
| Annual cost | Car A | Car B |
|---|---|---|
| Energy | £1,647.96 | £571.43 |
| Depreciation | £2,666.67 | £3,500.00 |
| Other annual costs | £1,755.00 | £1,805.00 |
| Annual total | £6,069.62 | £5,876.43 |
| Three-year total | £18,208.87 | £17,629.29 |
Car B saves £579.59 over three years using unrounded calculations. If its resale value is £2,000 lower, Car A becomes £1,420.41 cheaper. The decision is sensitive to depreciation even though the EV’s energy cost is lower.
Why This Matters for UK Drivers
Use current value for a car you already own and purchase price for one you might buy. What you paid for the existing car years ago is a sunk cost and does not measure its future depreciation from today. Enter a plausible resale value at the end of the selected period. If you are unsure, use a range. The resale sensitivity is often more informative than treating one distant valuation as certain.
Finance needs particular care. Where purchase and resale values already capture depreciation, adding the full loan repayments would count capital twice. Enter interest and fees as financing cost, and assess affordability of repayments separately. The mileage crossover changes both cars to the same annual distance while holding the entered fixed costs constant. Real maintenance and resale values can change with mileage, so the crossover is a model boundary rather than a guaranteed threshold for every driver.
Interpreting the result in practice
Depreciation and affordability answer different questions. Depreciation measures value consumed over ownership, while a loan repayment includes repayment of capital as well as financing cost. A car can have a lower modelled economic cost but require an unaffordable initial payment. Keep a separate cash-flow schedule for deposits, repayments and the sale proceeds, and do not interpret this comparison as an assessment of borrowing suitability.
What the result includes
The comparison combines energy, depreciation and the recurring ownership costs you enter. It deliberately keeps every assumption visible so you can change one variable at a time rather than relying on a hidden vehicle-cost database.
Mileage-driven cost
Petrol/diesel/hybrid uses your real UK MPG and pump price. EV uses your miles-per-kWh and blended charging price.
Capital cost
Depreciation is the fall from current/purchase value to expected value after the selected ownership period.
Recurring ownership cost
Insurance, tax, servicing/repairs, tyres, MOT, finance and other costs are added annually.
Break-even mileage
Where the maths permits it, the tool estimates annual mileage at which the two annualised cost models are equal.
How to improve the comparison
- Use your own recent MPG or EV efficiency rather than a brochure figure.
- For EVs, use a realistic blended charging price if you mix home, off-peak and public charging.
- Use insurance quotes for the actual vehicles and driver profile.
- Do not double-count finance principal as a running cost: depreciation already represents loss of vehicle value. Enter only finance interest and fees in the finance field.
- Run a second scenario with lower resale value or higher repairs to see how sensitive the decision is.
Frequently asked questions
Can I compare a hybrid?
A non-plug-in hybrid can use its measured UK MPG. This tool does not model a plug-in hybrid’s mixed electric and fuel operation. Use measured total annual running costs in the keep/change calculator or model its fuel and electricity separately.
Does this include opportunity cost of cash?
No. Finance interest and fees can be entered directly, but the foregone return on cash tied up in a vehicle is not modelled.
Why are future repairs and resale uncertain?
They depend on vehicle condition, market prices and events that cannot be known in advance. The calculator is most useful when you test more than one plausible scenario.