What it really costs to run a car in the UK in 2026, and why every published figure disagrees

No UK public body publishes what it costs to run a car, which is exactly why no two published figures agree: each is assembled from sources measuring different things, on different populations. Add up the lines that can be sourced and a petrol car at 40 mpg, on the average mileage, comes to about £2,621 a year — fuel at today's pump prices, the average insurance premium paid, vehicle tax, an MOT and the average household spend on repairs. That is our arithmetic, not anybody's published figure. The nearest official number is narrower again: the Office for National Statistics puts the average UK household at £14.30 a week on vehicle insurance, £9.50 on repairs and servicing, £18.40 on petrol, diesel and motor oils and £4.00 on vehicle road tax, £46.20 a week or about £2,402 a year, but those averages include households that spent nothing. Both understate a real car, because neither covers depreciation, the largest cost of ownership and the one no UK body measures.

Four sources, four different things measured

Two websites can quote wildly different running costs for the same car without either being wrong. Most UK figures trace back to these four sources, and they measure different things.

What households spend, and the caveat that matters

ONS splits that fuel line into £11.90 a week on petrol and £6.50 on diesel, and puts transport at 14.2% of weekly household spending of £676.60.

The caveat is the important part. These are averages across all households, including those with no car and those that spent nothing in the survey period. A household that runs a car spends more than every line above, by an amount ONS does not publish. Read it as a floor, not a bill.

Insurance: one average, and why it is close to useless alone

The Association of British Insurers puts the average annual motor premium at £566 in the second quarter of 2026, for comprehensive cover on privately owned cars, published 29 July 2026. That is the price paid on policies people bought, not a comparison-screen quote. The series peaked at £635 in early 2024.

One national mean tells a driver very little. The FCA's figures — England and Wales only, and regression-adjusted, meaning modelled rather than observed prices — put 17 to 24 year olds at £1,019 and the area spread at £356 in Ipswich to £767 in West London. Our post on the cheapest cars to insure for new drivers covers the young end.

The MOT: a small fee with an unpredictable bill behind it

In Great Britain the DVSA maximum fee for a class 4 car is £54.85; garages may charge less. Northern Ireland differs: the DVA charges £38.00 for a full car test and £29.50 for a retest — set prices at its own centres, not maximums.

The fee buys the test and nothing else. DVSA data for 2025/26, classes 3 and 4, shows 27.51% of initial tests failed, with 2.39 defects per failure — a national rate across every car tested, not the probability that yours fails. A minor defect still passes and an advisory is not a failure, so budget repair work separately. Our MOT guide and the MOT failure data show where defects fall; MOT check dates the next test.

Fuel: the one line you can work out exactly

DESNZ publishes UK pump prices weekly: in the week commencing 31 August 2026, petrol was 161.61p a litre and diesel 183.49p. A gallon is 4.546 litres, so petrol costs about £7.35 a gallon and diesel about £8.34. Divide by mpg for pence per mile.

At the DfT's England average of 7,100 miles, a petrol car at 40 mpg burns about £1,306 of fuel a year; at 30 mpg it burns £1,739. Both are arithmetic on a published pump price and a self-estimated mileage, not statistics: the DfT's figure for petrol cars alone is 6,200 miles a year, and 8,300 for diesel.

Electricity: the widest variable in the whole calculation

The DfT assumes 3.5 miles per kWh, including charging losses. At that efficiency the price per kWh decides everything, and the range is enormous.

Public rapid charging at peak rates costs more per mile than petrol, and stays dearer at every mpg from 30 to 60. That undoes most electric-versus-petrol comparisons, which assume home charging. A driver with no off-street parking cannot reach the cheap overnight tariffs at all, so two identical cars can differ elevenfold per mile on where they plug in.

None of those prices holds still. The operator tariffs were checked on 9 September 2026 and are commercial offers that change without notice. The Ofgem cap is Great Britain only and moves on 1 October 2026, when it is quoted excluding VAT because GB domestic electricity is zero-rated to 31 March 2027; Northern Ireland sits outside that cap entirely, with its own regulator and VAT unchanged at 5%. Home electricity carries 5% VAT and public charging 20%. Our EV charging costs guide holds the current figures and the EV charging cost calculator prices your own mileage. For a running-cost total the spread is the point, not any one week's tariff.

Vehicle tax: three regimes, three answers

One trap catches used electric buyers: a car first registered between 1 April 2017 and 31 March 2025 pays the £200 rate and no supplement at any list price, because electric cars only lost their exemption on 1 April 2025 — our guide to the expensive car supplement on used EVs works through what that is worth. Tax does not transfer with the car either: it is cancelled and refunded to the seller, so a buyer must tax it before driving. The VED rates guide has every band; the car tax calculator prices a specific car.

Depreciation: the largest cost, and nobody official measures it

Everything above leaves out the biggest number. No UK public body publishes used-car depreciation: there is no DVLA, DfT, ONS or DVSA series for what a car loses in value per year, per model or per mile. Any site showing a depreciation figure — a percentage in year one, a five-year residual — has estimated it, usually from its own trade data, and cannot point you at an official source, because none exists.

That is no reason to treat it as small. Put arbitrary numbers on it and the scale shows: a car bought at £15,000 and sold three years later at £9,000 has cost £2,000 a year in depreciation alone. Those are an illustration of the arithmetic, not a typical rate, because no measured UK rate exists — but the scale is the same as everything else here combined. You have to estimate it yourself, from what comparable cars of different ages are advertised at today — an observation about a live market, not a statistic, and the number most running-cost tables quietly invent.

Putting it together

No single source produces a total, so here is the arithmetic, each line's origin named: a petrol car at 40 mpg, on the DfT's average mileage, registered after April 2017 and tested in Great Britain.

Be honest about that total. It mixes an England mileage figure with a UK insurance average and an all-households repair average — each measured on a different population, none designed to be added to the others. It is also low: it leaves out depreciation, MOT repair work, parking, breakdown cover, finance interest and daily charges such as London's £12.50 ULEZ. Those charges are narrower than they sound: in England only Birmingham and Bristol charge cars outside London, Scotland's low emission zones have no daily charge you can choose to pay and issue penalties instead, and Northern Ireland has no zone of any kind. The clean air zone checker settles it per car and city, and whether your car pays in the ULEZ has its own answer.

There is no official rule for how much of your income a car should take, either: the 20%-of-take-home-pay and 20-4-10 rules are American folklore, and no UK body publishes an affordability ratio. Three things survive all of this: every published total is built from sources measuring different things, electricity swings the answer further than any other line, and depreciation, the biggest cost, is always somebody's estimate. Work backwards from a monthly budget in the car affordability calculator, then see what that buys in the listings.