The full picture
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Per-option summary over your chosen horizon
| Option | Power | Running p/mile | All-in p/mile |
Fuel/elec /yr | Depreciation /yr | Fixed /yr | Total over horizon |
How the maths works
- Fuel = (miles ÷ MPG) × 4.546 × £/litre (UK gallon).
- Electricity = (miles ÷ miles-per-kWh) × a blended £/kWh from your
home / public / solar charging mix — solar miles can be near-free.
- Cumulative cost = running costs + depreciation (reducing-balance)
+ repairs. Buying a car isn't treated as an instant loss — it becomes an asset that
then depreciates, which is what makes "keep vs switch" a fair comparison.
- Break-even = the year the switch's cumulative cost drops below
keeping your current car (the dashed line on the chart).
Does the current car's age matter?
Mostly it's already baked into the car's current value — an
older car is simply worth less, so there's less left to depreciate. What age adds on top
is rising repair risk and limited remaining life:
a 15-year-old car may not survive a 7-year comparison at all. Those aren't captured
automatically, so set a realistic Repairs £/yr (and shorten the horizon if the
car likely won't last it). The Age field flags this for you.
Why solar changes everything here
Charge largely from home solar and the marginal cost of those miles is close to zero —
an EV's running cost can fall to 2–3p/mile against
14–20p/mile for petrol or diesel. Set your realistic home / public /
solar split per car to see it.
Why servicing, insurance & road tax differ
- Servicing is usually cheaper for EVs — no oil, fewer moving parts,
and regenerative braking spares the brakes; ICE cars need more frequent, pricier
services (Energy Saving Trust).
- EVs can cost more to insure — expensive batteries, specialist
repairers and longer repair times push premiums up, even though they're cheaper to run
(ABI,
Thatcham Research).
- Road tax (VED) changed in April 2025 — EVs registered before then
paid £0; newer EVs now pay the standard rate (~£195/yr), plus the expensive-car
supplement above £40,000 (gov.uk VED tables).
Next steps
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Other UK calculators & the sources behind the defaults
Tools that do similar comparisons (and where the default figures come from):
Default rates are illustrative UK 2026 values (petrol ≈ £1.40/L, home electricity ≈ 27p/kWh,
rapid public ≈ 79p/kWh). Always replace them with your own quotes.
Guidance only, not financial advice. Real costs depend on your tariff, driving and the
specific cars. This tool stores no personal data and has no backend.