What a used car really costs to run

What a year actually looks like

Three comparable family cars, driven the same 8,000 miles, with servicing, tyres and insurance held identical so the comparison is about the things that genuinely differ.

The gap is smaller than the internet usually suggests. Electricity is dramatically cheaper per mile, but road tax now applies to electric cars too, and the fixed costs — insurance, servicing, tyres — do not care what is under the bonnet.

Road tax: the flat rate that surprises people

For any car first registered on or after 1 April 2017, road tax is a flat standard rate of £200 a year. Not banded by emissions, not cheaper because it is a small engine. A city runabout and a large estate pay exactly the same.

Cars registered before April 2017 still sit in the older emissions-based bands, which is why an older diesel can occasionally be cheaper to tax than a newer petrol.

Fuel, and why diesel stopped winning

Diesel engines still travel further on a gallon. The problem is what a gallon costs. At 1.60 a litre for petrol against 1.79 for diesel, a diesel needs a meaningful economy advantage simply to break even.

Diesel makes sense on mileage, not on principle. Below about twelve thousand miles a year, the sums rarely favour it.

There is a second consideration that does not show up in pence per mile. Diesel particulate filters need sustained hot running to clear themselves. A diesel used for short, cold trips will eventually present you with a bill that no fuel saving covers.

Electric: cheaper per mile, if you can charge at home

At the capped rate of 26.11p per kilowatt hour, a typical electric car costs roughly a third of an equivalent petrol one to move. That is the entire economic case, and it is a strong one.

It rests on charging at home. Public rapid charging can cost three or four times the domestic rate, and at that point the running-cost advantage over petrol largely evaporates. Before buying electric, the question is not which car — it is whether you have a driveway.

• Off-street parking and a home charger: the numbers work comfortably.
• Occasional public charging on longer trips: still ahead, by less.
• Public charging as your main source: run the sums properly first.

The cost nobody budgets for

Depreciation is almost always the largest number in car ownership, and it is invisible because you never write a cheque for it. A car losing £2,000 of value in a year has cost you more than its fuel, tax, servicing and tyres put together.

This is the strongest argument for buying used rather than new. The steepest part of the curve happens in the first three years, to somebody else. A well-chosen three-year-old car gives you most of the modern equipment and very little of the drop.

1. Buy after the cliff, not before it. Years three to six are the flattest part of most depreciation curves.
2. Popular colours and sensible specifications hold value. Unusual choices cost you twice — once when nobody wants it, once on the time it takes to sell.
3. Keep the history. A complete service record is worth real money at resale, and costs nothing to maintain.

Where these numbers come from

Fuel and electricity prices move constantly, so it matters where a figure came from and when. Everything quoted here is published, and the same values drive the cost panel on every car on this site — so the article and the listing can never contradict each other.

• Pump prices: DESNZ weekly road fuel prices, week commencing 3 August 2026.
• Electricity: Ofgem energy price cap, 1 July to 30 September 2026.
• Road tax: GOV.UK vehicle tax rate tables.

Last reviewed 5 Aug 2026. Every car in our showroom shows its own estimated running costs, worked from these same figures and its actual economy.