The 4p calculation: how to work out your car's charge cost
The maths is straightforward. Take your car's battery capacity in kilowatt-hours, multiply by the price per kWh, and you have the cost of a full charge from empty.
Battery capacity (kWh) multiplied by 0.04 equals cost in pounds at a 4p rate. A 60kWh battery at 4p = £2.40. A 40kWh battery at 4p = £1.60. A 77kWh battery at 4p = £3.08.
In practice, you rarely charge from completely empty to completely full. Most EV drivers maintain a charge level between 20% and 80% for daily use, with occasional full charges for longer journeys. Your real-world charge cost is proportionally lower. But the full-charge figure is the cleanest comparison point, so that's what we use throughout this guide.
One important note: charging efficiency means a small amount of electricity is lost as heat during the charging process. Home AC charging (7kW wallbox or standard socket) is typically 85-90% efficient, meaning you pay for slightly more kWh than the battery stores. The figures below use nominal battery capacity, so your actual bill may be 10-15% higher to account for this.
Every popular UK EV: full charge cost across four price scenarios
The table below shows the cost of a full charge for the most common UK electric cars at four different unit rates: the overnight Agile minimum (4p), a typical overnight Agile average (8p), the July 2026 Ofgem price cap rate (26.11p), and an Agile peak evening price (38p).
| Vehicle (battery size) | 4p/kWh | 8p/kWh | 26.11p (cap) | 38p (peak) |
|---|---|---|---|---|
| Tesla Model 3 SR (60kWh) | £2.40 | £4.80 | £15.67 | £22.80 |
| Nissan Leaf (40kWh) | £1.60 | £3.20 | £10.45 | £15.20 |
| VW ID.4 (77kWh) | £3.08 | £6.16 | £20.10 | £29.26 |
| BMW iX3 (74kWh) | £2.96 | £5.92 | £19.32 | £28.12 |
| Vauxhall Corsa Electric (50kWh) | £2.00 | £4.00 | £13.06 | £19.00 |
| Kia EV6 (77kWh) | £3.08 | £6.16 | £20.10 | £29.26 |
The difference between the 4p and 38p columns is what separates an Agile EV driver from someone who charges at the wrong time. For a VW ID.4, that's £26.18 per charge. Do that twice a week and you're paying £2,722 more per year than you need to.
Even comparing 4p to the standard price cap of 26.11p, the annual difference for a regular VW ID.4 driver (100 full charges per year) is £1,702. This is why the decision about when to charge on Agile is the single most financially significant EV decision most drivers make.
Petrol equivalent: cost per mile on Agile vs filling the tank
To make the comparison meaningful, you need a cost-per-mile figure. At 4p/kWh and a real-world efficiency of 3.5 miles per kWh, the cost per mile on Agile overnight is 1.14p. Just over one penny per mile.
A petrol car achieving 35mpg at the current UK average pump price of 140p/litre travels approximately 15.9 miles per litre. At 140p, that's 8.8p per mile. Round it to 9p per mile for a typical UK driver in typical conditions.
Electric on Agile overnight: 1.14p per mile. Petrol: approximately 9p per mile. Electric is 87% cheaper per mile on fuel costs alone. If you use a slightly more efficient EV (4 miles per kWh), the electric figure drops further to 1p per mile exactly. The comparison is not close. The gap is structural, not marginal.
Annual saving for a 10,000-mile driver
The UK average annual mileage is around 9,000-10,000 miles. For a driver covering exactly 10,000 miles per year in an EV with 3.5 miles/kWh efficiency, total annual electricity consumption is approximately 2,857 kWh.
At 4p/kWh on Agile overnight: £114 per year in charging costs.
At 26.11p/kWh on a standard tariff: £746 per year.
Saving versus standard tariff: £632 per year.
Versus petrol in a 35mpg car: 10,000 miles uses 1,295 litres at 140p = £1,813.
Saving versus petrol: approximately £1,699 per year.
The £114 figure deserves a moment's attention. That's the total annual fuel cost for 10,000 miles of driving. Less than £10 per month. Less than a single tank of petrol for most family cars. At this cost level, the economics of EV ownership look fundamentally different from the petrol era.
To find the actual rate available tonight and calculate your specific saving, check AgileAlert's live price display. On many nights, the overnight rate is below 4p, making these figures even more favourable.
Annual saving for a 20,000-mile driver
Higher-mileage drivers see even more dramatic figures. Sales reps, tradespeople, and regular long-distance commuters often cover 20,000 miles or more per year. For these drivers, Agile overnight charging represents one of the most significant personal finance opportunities available.
20,000 miles at 3.5 miles/kWh = 5,714 kWh per year.
At 4p/kWh: £229 per year.
At 26.11p standard tariff: £1,492 per year.
Saving versus standard tariff: £1,263 per year.
Petrol at 20,000 miles/year: 2,590 litres at 140p = £3,626.
Saving versus petrol: approximately £3,397 per year.
A 20,000-mile-per-year driver switching from petrol to an EV charged on Agile overnight saves the equivalent of a significant portion of their annual salary in running costs. Over five years, that's close to £17,000 in fuel savings, purely from the Agile overnight rate.
What this means for total cost of EV ownership
EVs still carry a purchase premium over equivalent petrol cars, though the gap has narrowed significantly as battery costs have fallen. In 2026, a mid-range electric hatchback typically costs £3,000-8,000 more than a comparable petrol equivalent when bought new.
At Agile overnight rates, the annual fuel saving for an average driver (10,000 miles) is roughly £1,700 versus petrol. The purchase premium is recovered in two to four years through fuel savings alone, before accounting for lower servicing costs.
EVs have significantly fewer moving parts than petrol cars. No oil changes, no spark plugs, no timing belt, no catalytic converter, no gearbox oil. Brake pads last longer thanks to regenerative braking. A typical annual service is simpler and cheaper. Industry estimates suggest EV servicing costs run 30-40% lower than petrol equivalents over a five-year period.
When you combine the Agile overnight fuel saving with lower maintenance costs, the total-cost-of-ownership calculation for EVs in the UK in 2026 is compelling at almost any mileage above 8,000 miles per year. At 10,000+ miles, the numbers strongly favour the switch.