Track cumulative ownership cost for an electric car and a petrol car side by side, and find the year they break even.
Each year, petrol running cost is (annual miles ÷ mpg) × 4.546 litres/gallon × price per litre, plus a fixed annual maintenance figure. EV running cost is annual miles ÷ miles-per-kWh × price per kWh, plus its own (lower) maintenance figure. Both are added to their year-1 purchase price and accumulated year over year; the break-even year is the first year the EV's cumulative cost drops to or below the petrol car's.
At roughly 40mpg and £1.50/litre, a petrol car covering 100 miles costs around £7.50 in fuel; a modern EV at 3–5 miles/kWh charging at around 28–32p/kWh covers the same 100 miles for roughly £6–£9 on public rates, or notably less — often £4–£6 — charging at home overnight. EVs also need far less routine maintenance: no oil changes, no exhaust system, and brake pads that last much longer thanks to regenerative braking.
Battery replacement (currently estimated at roughly £7,000–£12,000 if it's ever needed, though most batteries outlast typical ownership), insurance (EVs often run 10–20% higher), and UK road tax (zero-emission vehicles pay none, while petrol cars pay £190–£370+ depending on CO2 rating) are not modelled here but all tilt further in the EV's favour over time.
This simulation tracks cumulative ownership cost for a petrol car and an equivalent electric car, adding each year's fuel or electricity cost and maintenance on top of the purchase price. The point where the EV's cumulative-cost curve drops below the petrol car's is the break-even year — the moment the EV's higher upfront price has been paid back by lower running costs.
Two cumulative-cost lines climbing year by year: petrol (red) and electric (green), starting from their respective purchase prices. A pulsing marker highlights the year the two lines cross — the break-even point where total EV ownership cost first drops below total petrol ownership cost.
Set your annual mileage, projection years, petrol and electricity prices, the EV's purchase premium over a comparable petrol car, and each vehicle's efficiency (mpg for petrol, miles/kWh for EV). Higher annual mileage and higher fuel prices both pull the break-even year earlier.
A typical EV needs only around £300–£600 in servicing over five years, versus roughly £800–£1,500 per year for a petrol car once oil changes, brake wear and exhaust repairs are counted — a gap that alone can be worth several thousand pounds over a decade of ownership.
Annual fuel cost is (annual miles ÷ miles-per-gallon) × 4.546 litres per imperial gallon × the price per litre, plus a fixed annual maintenance allowance for servicing, oil changes and brake wear.
Annual energy cost is annual miles ÷ the car's efficiency in miles-per-kWh × the price per kWh, plus a smaller fixed annual maintenance allowance, since EVs have far fewer moving parts and no oil or exhaust system to service.
It is the first year in which the EV's cumulative cost (purchase price plus accumulated running costs) drops to or below the petrol car's cumulative cost. Before that year the EV's higher purchase price still outweighs its running-cost savings; after it, the EV is cheaper overall.
If annual mileage is low, or the purchase premium is large relative to the fuel/electricity price gap, the running-cost savings each year may be too small to ever overtake the higher upfront cost within the years you've projected. Higher mileage and a bigger price gap between petrol and electricity both bring the break-even point closer.
Battery replacement (rarely needed within typical ownership, but costly if it happens), insurance (often 10–20% higher for EVs), and UK road tax (zero for EVs, £190–£370+ per year for petrol cars depending on CO2 emissions) are not included, and all of them would tilt the comparison further toward the EV.