Is an electric car cheaper to run than diesel now? The pence-per-mile numbers

The pence-per-mile table

Every figure below uses the same method. For petrol and diesel: pence per litre × 4.54609 (the litres in an imperial gallon; the Vehicle Certification Agency’s fuel-cost method rounds it to 4.546) ÷ miles per gallon. For electric: pence per kWh ÷ miles per kWh. The cars are like for like: Volkswagen’s official WLTP figures for the Tiguan, a family SUV sold as both petrol and diesel, set against an electric car at 3.18 miles per kWh, which is the average of every EV Which? has lab-tested, with charging losses counted, so it is energy drawn from the socket. Fuel prices are the RAC’s UK averages for 28 September 2026. Electricity is Ofgem’s price cap unit rate for 1 October to 31 December 2026, Octopus’s overnight EV rate from 1 October, and Zapmap’s August 2026 public charging averages, the latest published.

Diesel: about 17.3p a mile. 199.18p a litre (RAC, 28 September 2026, the new record) × 4.54609 = 905.5p a gallon, about £9.05. The Tiguan 2.0 TDI 150PS Life DSG is rated 52.2 mpg (WLTP combined). 905.5 ÷ 52.2 = 17.3p.

Petrol: about 16.6p a mile. 174.13p a litre × 4.54609 = 791.6p a gallon, about £7.92. The Tiguan 1.5 eTSI 130PS Life DSG is rated 47.7 mpg. 791.6 ÷ 47.7 = 16.6p. Petrol is 25p a litre cheaper than diesel, but the diesel goes further on a gallon, which is why the gap per mile is under a penny.

Electric, charged at home on the price cap: about 8.3p a mile. Ofgem’s cap rate for electricity from 1 October is 26.32p per kWh (Great Britain average, Direct Debit), and there is no VAT on domestic electricity in Great Britain from 1 October 2026 to 31 March 2027. 26.32 ÷ 3.18 = 8.3p, a little under half the diesel figure.

Electric, charged overnight on an EV tariff: about 2.5p a mile. Intelligent Octopus Go charges 8p per kWh for smart charging from 1 October (8.4p before the VAT change), with a six-hour whole-home window from 11.30pm to 5.30am. 8 ÷ 3.18 = 2.5p. Other suppliers’ published overnight rates include EDF GoElectric at 6.66p (11pm to 6am; EDF prices it at 0% VAT, though the headline on its page still shows 6.99p, the old 5% figure), British Gas EV Power at 9.5p (midnight to 5am) and E.ON Next Drive at 10p (midnight to 6am), or 8.5p on E.ON’s smart version: 6.66 ÷ 3.18 = 2.1p; 9.5 ÷ 3.18 = 3.0p; 10 ÷ 3.18 = 3.1p; 8.5 ÷ 3.18 = 2.7p. British Gas and E.ON do not say whether their rates include VAT, and their pages are dated 24 and 23 September, before the VAT change. All of them need a smart meter, and the smart-charging tariffs need a compatible car or charger.

Electric, on a public rapid charger: about 24.2p a mile. Zapmap’s price index for August 2026 puts the weighted-average pay-as-you-go price at 77p per kWh on chargers of 50kW and above. 77 ÷ 3.18 = 24.2p, more than the diesel and more than the petrol. Across the ten biggest rapid networks prices ran from 59p to 92p: Tesla’s open sites at 63p work out at 63 ÷ 3.18 = 19.8p a mile, InstaVolt at 92p is 92 ÷ 3.18 = 28.9p. Slower public chargers (3kW to 49kW) averaged 54p: 54 ÷ 3.18 = 17.0p, level with the diesel.

The crossover is easy to work out. At 3.18 miles per kWh an electric car matches the petrol Tiguan at 16.6 × 3.18 = about 53p per kWh and the diesel at 17.3 × 3.18 = about 55p. Which? puts the line at around 51p on its own, older and lower, fuel prices. Pay less than that per unit and the electric car is cheaper per mile; pay more and it is not.

Where the inputs come from, and how much they matter

The efficiency figure moves the electric numbers most, so it is worth being clear about it. Which?’s 3.18 miles per kWh is the average across every model and version it has tested, in a lab at 20°C with the climate control on and more motorway running than the official test, and Which? says the test factors in charging losses. So do not knock another tenth off for losses: they are already counted (for scale, the German motoring club ADAC measured 5.1 to 7.0 per cent on an 11kW or 22kW wallbox). It is also a cautious figure: Volkswagen’s official WLTP consumption for the ID.4, its electric family SUV, is 16.1 kWh per 62 miles for the 58kWh Pure Essential, which is 62 ÷ 16.1 = about 3.85 miles per kWh, and EDF’s and British Gas’s own examples assume 3.5 and 3.3.

At 3.85 the electric rows fall to 26.32 ÷ 3.85 = 6.8p on the cap, 8 ÷ 3.85 = 2.1p overnight and 77 ÷ 3.85 = 20.0p on a rapid charger, which is still above the diesel. Bigger cars do worse: Which?’s 2023 table by size class ran from 3.6 miles per kWh for city cars to 2.8 for medium and large SUVs, and a big SUV on the cap rate is 26.32 ÷ 2.8 = 9.4p a mile.

The petrol and diesel figures cut the other way. WLTP is a laboratory test, and the Vehicle Certification Agency says its figures “cannot be fully representative of real-life driving conditions”. What Car?’s True MPG programme found petrol, diesel and hybrid cars averaging 8.2 per cent worse than their official figures across 168 models, though that analysis dates from 2022. Apply it and the diesel Tiguan does 52.2 × 0.918 = 47.9 mpg, or 905.5 ÷ 47.9 = 18.9p a mile; the petrol does 47.7 × 0.918 = 43.8 mpg, or 791.6 ÷ 43.8 = 18.1p. We have kept the official figures in the table because they are the ones the manufacturer publishes, which means the table, if anything, flatters the combustion cars.

The fuel prices are the RAC’s because the 2022 records were set on the RAC’s measure. Our own fuel price tracker, built from the retailer price files in the government’s open-data scheme, samples differently and updates daily; use it for today’s figure and redo the sum. Why diesel in particular has risen is covered in our diesel explainer.

What the per-mile figure leaves out

Fuel is one line in the cost of running a car, and the table says nothing about the others:

The purchase price and depreciation. We have no sourced, current comparison of what an equivalent electric car costs to buy or loses in value against a diesel, and no insurance comparison either, so we have left both out rather than guess. What we can say is that the Electric Car Grant is for new cars only, at first registration, with a recommended retail price of £37,000 or under (a few dearer versions of a qualifying model count, up to £42,000): up to £3,750 off for Band 1 cars and £1,500 for Band 2, included by the seller as a discount. It closes on 31 March 2030, the eligible list changes as models are approved, and the government says the grant level and criteria can change with no notice.

Vehicle tax. Electric cars stopped being tax-free in April 2025. A zero-emission car registered on or after 1 April 2025 pays £10 in its first year and then the standard rate, which is £200 a year for 1 April 2026 to 31 March 2027; zero-emission cars registered between April 2017 and March 2025 also pay £200. That is the same standard rate a petrol or diesel car registered since April 2017 pays, so from the second year vehicle tax does not change the comparison. The expensive car supplement starts at a different price: over £50,000 list price for a zero-emission car registered from 1 April 2025, over £40,000 for a petrol or diesel car. Either way it adds £440 a year for five years from the second licence, £640 a year in all.

A pay-per-mile charge from 2028. The government has announced Electric Vehicle Excise Duty from 1 April 2028: 3p a mile for battery-electric cars and 1.5p for plug-in hybrids, rising with CPI from 2029-30, declared with an odometer reading and a mileage estimate when you tax the car. It is policy with draft legislation out for technical consultation, not yet law. When it arrives it adds 3p to every electric row above: about 11.3p on the cap, 5.5p overnight, 27.2p on a rapid charger. At 7,100 miles it is 7,100 × 3p = £213 a year. The Treasury describes 3p as half the equivalent rate of fuel duty.

Winter. Cold weather cuts an electric car’s efficiency. What Car?’s summer-and-winter range test of three EVs (a BMW i4, a Cupra Born and a Tesla Model Y) found winter range an average of 18 per cent short of summer, when it had been 24 to 29°C. Cost per mile rises roughly in step, so at 3.18 × 0.82 = 2.61 miles per kWh the cap-rate cost is 26.32 ÷ 2.61 = about 10.1p a mile and the overnight cost 8 ÷ 2.61 = about 3.1p. Petrol and diesel cars also use more fuel in the cold, but we found no comparable published figure, so the table adjusts neither side.

The rest of your electricity. An EV tariff’s cheap window is paid for by a dearer daytime rate. Octopus’s public tariff data on 28 September showed Intelligent Octopus Go’s London day rate at 35.481p per kWh excluding VAT, the rate that applies from 1 October, against the cap’s Great Britain average of 26.32p: about 9p a unit more for everything you use outside the window. Whether the tariff wins overall depends on how much of the household’s use you can move into it. EDF, British Gas and E.ON did not publish their day rates on the pages we read, so get a quote.

VAT and the cap. The 0% VAT on home electricity in Great Britain runs to 31 March 2027 and returns to 5% unless the government extends it: 26.32 × 1.05 = 27.6p, or 8.7p a mile at 3.18. Ofgem’s cap changes again on 1 January 2027. A fixed EV tariff locks its rate but not its VAT treatment. Public charging is standard-rated at 20%, and HMRC’s position is that it stays so, though it notes a tribunal decision the other way that it is seeking permission to appeal.

A home charger. Which? says a home charger typically costs £500 to £1,200 to buy and install, and a 7kW one about £900; Pod’s Solo 3S, for example, is £999 with a standard installation included. The OZEV grant of 75 per cent up to £500 is only for flat owners and renters with their own private off-street parking, and for households without off-street parking who fit a cross-pavement channel. Both close on 31 March 2027, and someone who owns and lives in a house gets nothing towards a charger on their own drive.

Who comes out ahead, and who doesn’t

Over a year the differences are large. The Department for Transport’s National Travel Survey puts the average car in England at 7,100 miles in 2025 (petrol cars 6,200, diesel 8,000, battery-electric 9,400). Using the same 7,100 miles for every car, so the comparison is fair: the diesel Tiguan burns 7,100 × 17.3p = about £1,230 of fuel a year; the petrol, about £1,180; the electric car needs 7,100 ÷ 3.18 = 2,233 kWh, which is about £590 on the cap rate, about £180 on the 8p overnight rate and about £1,720 on rapid chargers.

Ahead: a driveway and an overnight tariff. This is where the electric case is strongest: about 2.5p a mile against 17.3p, roughly £1,050 a year less than the diesel at 7,100 miles. Zapmap says around 85 per cent of all EV charging happens at home. The more you drive, the bigger the gap: at the 9,400 miles the average battery-electric car covers, 9,400 × (17.3 − 2.5)p is about £1,390; at a petrol car’s average 6,200 miles it is about £920.

Still ahead: a driveway on the ordinary cap rate. No special tariff, no smart charger, and it is still about 8.3p against 17.3p: about £640 a year less than the diesel at 7,100 miles.

Level or behind: no home charging. If you cannot charge at home and rely on the public network, the arithmetic turns. Rapid chargers at Zapmap’s 77p average cost about 24.2p a mile, about 7p more than the diesel and about £490 a year more at 7,100 miles; even at Tesla’s 63p it is 19.8p, above both combustion cars. Slower public chargers at 54p come in level with the diesel at 17.0p. Zapmap’s index is pay-as-you-go prices and leaves out memberships and deals, and Zapmap says the average price actually paid is lower; but someone charging only on the motorway network is not saving money against a diesel at today’s prices, record or not.

In between: on-street parking with a workaround. Households without off-street parking can, where the council allows it, fit a cross-pavement channel so a cable runs from the house to the kerb. The decision rests with the local authority, not every council permits one, and it gives no right to the parking space outside. Kerbo Charge, one supplier, advertises installed channels from £999 including VAT and council permissions, and says the council sets the exact price, which may be higher. The OZEV on-street grant pays 75 per cent up to £500 towards buying and installing the chargepoint socket, not the channel; it needs highways consent and planning permission, an OZEV-approved installer and an eligible chargepoint, and closes on 31 March 2027. Done, it moves you into the home-charging column.

If you are weighing it up

Start from your own car, not ours. Take your real mpg from the trip computer or a full-tank-to-full-tank check, and today’s price from the tracker: price × 4.54609 ÷ mpg. For the electric side, use the rate you would actually pay: the cap rate if you would charge whenever you like, an overnight rate only if you have a driveway, a smart meter and can keep the car plugged in during the window, and 77p if you would live on rapid chargers. Vehicle tax is the same £200 standard rate for both from the second year, so leave it out; from April 2028, add 3p a mile to the electric side.

Then weigh the things the table cannot: what you would pay for the car, what your current one is worth, insurance quotes for both, and whether you can charge at home at all. The fuel saving is real; whether it outweighs the rest is a sum only you can do, with your own numbers.