The £7 fill-up, and why most drivers never get it
An off-peak tariff turns a full charge into about £6 of electricity. The same charge on a motorway rapid costs nearly ten times that. Almost nothing about the car changes the answer.
The cheapest and most expensive ways to put the same electricity into the same car differ by more than ten times. That is the single most important fact about running an electric vehicle, and it has almost nothing to do with which car you bought.
The three prices
Take a 60 kWh usable battery, charged from 20% to 80% — 36 kWh of energy into the battery, roughly 40 kWh drawn from the grid once charging losses are included.
| Where you charge | Unit price | Cost of that charge |
|---|---|---|
| Off-peak home tariff | ~7p/kWh | £2.80 |
| Standard home rate | ~26p/kWh | £10.40 |
| Motorway rapid | ~85p/kWh | £34.00 |
A full 0–100% charge on the same car is roughly £4.50 off-peak against £48 on a motorway rapid.
Why most people don't get the cheap number
The off-peak rate is not automatic. It requires three things to line up, and most households miss at least one.
A tariff with a cheap overnight window. These exist from several suppliers, typically offering a low rate for a fixed block overnight. They are not the default; you have to move onto one deliberately.
Somewhere to charge at home. Roughly a third of UK households have no off-street parking. Without a driveway or an allocated bay, the cheap rate is largely out of reach — though see our guide on charging without a driveway for the options that do work.
A charger or car that can schedule. The window is usually a handful of hours in the small hours. Plugging in at 6pm and charging immediately means paying the day rate for most of the session. Any smart charger, and most cars, can delay the start.
Worth knowing: the tariff's cheap window is usually paired with a higher daytime unit rate. If your car sits unused most weeks, running the numbers on your actual consumption matters more than the headline overnight price.
What this means per mile
Efficiency varies, but 3.5 to 4.5 miles per kWh covers most modern EVs in mixed driving.
At 4 mi/kWh:
- Off-peak home: 1.8p per mile
- Standard home rate: 6.5p per mile
- Motorway rapid: 21p per mile
A petrol car at 45 mpg with fuel around £1.40 a litre runs at roughly 14p per mile. So home charging is dramatically cheaper, and motorway rapid charging is more expensive than petrol.
That last point surprises people, and it is the reason the driveway question matters so much.
The realistic mix
Very few drivers are 100% home or 100% public. A common pattern is 80% home and 20% rapid, which at the prices above works out around 5.6p per mile — still comfortably under half the petrol equivalent.
Our charging cost calculator takes your battery size, your tariff and your charging split and gives you the figure for your situation rather than an average.
What to actually do
- Find out what you pay now. The unit rate on your electricity bill, in pence per kWh, is the number that matters.
- Check whether an off-peak tariff is available to you. It usually requires a smart meter.
- Schedule your charging into the cheap window, from the charger or the car.
- Treat rapid charging as a travel cost, not a routine one.
The gap between doing this and not doing it, over 10,000 miles a year, is several hundred pounds.
In pictures
Common questions
Is an EV-specific tariff always cheaper?
Only if you can shift most of your charging into the off-peak window. EV tariffs usually raise the daytime unit rate to fund the cheap overnight one, so a household that charges at random times can end up worse off.
Does rapid charging damage the battery?
Occasional rapid charging is what the system is designed for. Exclusive rapid charging, especially to 100% and in high heat, accelerates degradation slightly. For most drivers the cost difference matters far more than the wear.
About the author
ElectraMile EditorialEditorial desk
The ElectraMile editorial team covers charging, running costs and EV ownership for readers in the UK and US.
Spotted something wrong? Tell us — we correct and date every change.
Figures shown for United Kingdom in GBP. Switch market in the header to see local pricing and terminology.
