The fair comparison methodology
A meaningful comparison requires a level playing field. We use the following assumptions throughout this article.
Vehicle class: medium family hatchback or crossover. Think VW Golf vs Vauxhall Corsa Electric, or VW Passat vs VW ID.4. Similar interior space, similar functionality, similar target market.
Annual mileage: 10,000 miles, close to the UK average of 9,000-10,000 miles per year. We also include 20,000 miles for higher-mileage drivers.
Petrol car: 35mpg combined economy, a realistic figure for a modern efficient petrol hatchback. Fuel price: 140p/litre, current UK average in 2026.
Electric car: 3.5 miles per kWh real-world efficiency, achievable in typical UK driving conditions. Charging split: 80% home charging on Octopus Agile overnight at an average of 4p/kWh, and 20% public charging at the UK average public charging rate of approximately 35p/kWh.
This 80/20 home/public split reflects the actual usage pattern of most UK EV drivers with home charging capability. Drivers without home charging will see higher costs due to greater reliance on public charging, though the comparison remains favourable for EVs at all but the most public-charging-heavy usage patterns.
Petrol cost: 10,000 miles in a typical family car
The arithmetic for petrol is simple and expensive.
10,000 miles at 35mpg requires 285.7 gallons of fuel. In litres (multiply by 4.546), that's 1,299 litres. At the current UK average price of 140p/litre, the fuel cost comes to £1,818.
In practice, real-world fuel costs are slightly higher. Motorway driving at constant speed can approach the official economy figure. Urban driving, short trips, and cold weather reduce it. Air conditioning increases consumption. The figure of £1,800-2,000 per year in petrol for 10,000 miles is consistent with what UK drivers actually report spending.
Beyond fuel, petrol cars require regular servicing. Typical annual service costs (oil change, filter, inspection) run £200-400 for a standard family hatchback. Every 30,000-40,000 miles, additional items (brakes, tyres, timing belt) add further costs. Annual servicing is genuinely cheaper for EVs, as we discuss later.
EV cost on standard tariff: the baseline
Before introducing Agile, it's worth establishing what an EV costs to run on a standard tariff. This dispels the common myth that EVs are expensive to charge at home.
10,000 miles at 3.5 miles/kWh = 2,857 kWh per year. At the July 2026 Ofgem price cap of 26.11p/kWh, the annual charging cost is £746.
Even on a standard tariff, without any smart scheduling or Agile optimisation, an EV costs £746 per year to fuel versus £1,818 for petrol. The saving is £1,072 per year, just from the fuel cost difference, before any consideration of Agile.
This figure already demolishes the argument that EVs are expensive to run. They are substantially cheaper than petrol at standard UK electricity rates. Agile makes the gap even wider.
EV cost on Agile overnight: the real number
Here's where the comparison becomes genuinely dramatic. With the 80/20 home/public charging split and Agile overnight rates at home:
80% of 2,857 kWh = 2,286 kWh charged at home on Agile at an average overnight rate of 4p/kWh = £91.
20% of 2,857 kWh = 571 kWh charged at public chargers at 35p/kWh average = £200.
Total annual fuel cost: £291.
Against petrol at £1,818, the saving is £1,527 per year. Against a standard tariff EV at £746, Agile saves an additional £455 per year.
The £291 figure is the honest number for a typical UK Agile EV driver. It includes the reality of public charging for longer journeys, and it uses a conservative 4p/kWh home rate. On many nights, the Agile overnight rate falls below 4p. If you check AgileAlert and target the cheapest window, your effective home rate is likely even lower.
The public charging reality
The 20% public charging figure deserves attention because it's the element most petrol-driver-to-EV-consideration calculations underestimate.
Public charging in the UK has improved significantly. The UK's rapid charging network now covers most motorway service areas and many town centres. Rapid chargers (50kW-150kW) deliver roughly 100 miles in 20-30 minutes. Ultra-rapid (150kW+) chargers at motorway services charge significantly faster.
Public charging costs vary widely. Network tariffs range from around 25p/kWh for membership accounts up to 85p/kWh for pay-as-you-go rapid chargers. The 35p/kWh figure used in our calculation is a realistic average for a driver who occasionally uses pay-as-you-go rapid charging but also uses cheaper networked options where available.
Even at 50p/kWh for all public charging (a pessimistic assumption), the total annual cost for our 10,000-mile driver would be: £91 home + £286 public = £377. Still comfortably below £746 on a standard tariff, and dramatically below £1,818 for petrol.
Drivers who charge primarily at public chargers (apartment dwellers without home charging, for example) will see higher annual costs. At 35p/kWh for all charging, 10,000 miles costs approximately £1,000. Still cheaper than petrol, but the Agile advantage is reduced or eliminated without home charging access.
The full cost comparison table
| Metric | Petrol car | EV on standard tariff | EV on Agile |
|---|---|---|---|
| Annual fuel/charging (10k miles) | ~£1,818 | ~£746 | ~£291 |
| Cost per mile (fuel only) | ~18p | ~7.5p | ~2.9p |
| CO2 per km (approx) | ~122g | ~45g (UK grid) | ~10-20g (overnight wind) |
| Annual servicing (est.) | £300-500 | £150-250 | £150-250 |
| 5-year running cost (fuel + service) | ~£10,900 | ~£5,730 | ~£2,455 |
The five-year running cost column is the number that changes minds. A petrol driver spends roughly £10,900 on fuel and servicing over five years at 10,000 miles per year. An Agile EV driver spends approximately £2,455. The difference is £8,445 over five years. That's a significant contribution toward the purchase premium of the EV itself.
The carbon comparison
The cost comparison makes a compelling case for Agile EV charging. The carbon comparison makes it a moral one too.
A typical petrol car emits approximately 122g of CO2 per kilometre. This is a direct tailpipe emission, independent of how the fuel was extracted or refined.
An EV charged on the UK grid emits approximately 30-60g of CO2 per kilometre on average (2026 figures), reflecting the UK's current electricity mix of roughly 50.8% renewables (Ember 2024 data). This is already a significant reduction. But the average misses the most important part of the Agile story.
Overnight Agile rates are cheapest when renewable generation is highest. When a driver charges during the cheapest Agile window, they are almost always charging on electricity generated predominantly by wind. The UK's offshore wind fleet generates most powerfully at night and during winter storms. These are also the times when Agile prices are lowest.
Wind generates electricity at approximately 10-15g CO2 per kWh over its full lifecycle. Against petrol's 2,392g CO2 per kilometre (well-to-wheel), charging on overnight Agile wind is effectively near-zero carbon personal transport by any meaningful comparison.
The personal finance win and the climate win are not separate things. They are the same thing, expressed differently. When you charge during the cheapest Agile window, you are charging on surplus renewable energy that the grid cannot otherwise fully absorb. Your cheap overnight charge is also your cleanest possible charge. The two motivations reinforce each other entirely.
Wind farms in 2026 are sometimes paid to curtail output because the grid cannot absorb all their generation overnight. When an EV owner charges during those hours, they directly reduce the need for curtailment. They are not just a passive beneficiary of cheap renewable energy. They are actively part of the system that makes renewable energy economically viable.
Total cost of ownership: the bigger picture
Purchase price is the last piece of the comparison. EVs still carry a premium over equivalent petrol cars at equivalent trim levels, though the gap has narrowed substantially.
A 2026 mid-range electric crossover (VW ID.4, Kia EV6, Vauxhall Mokka Electric) typically costs £3,000-8,000 more than a directly comparable petrol crossover. Used EVs close this gap further. A two-year-old Nissan Leaf or used Vauxhall Corsa Electric can be bought for comparable money to a used petrol equivalent.
At the Agile overnight running cost advantage of approximately £1,500-1,700 per year versus petrol at 10,000 miles, the purchase premium on a new EV is recovered in two to five years through fuel savings alone. Add servicing savings of £150-250 per year, and the payback period shortens further.
For a driver keeping a car for five years (the UK average), the total-cost-of-ownership calculation strongly favours the EV when home Agile charging is available. The upfront premium is a one-time cost. The running cost advantage repeats every year.