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EV vs Petrol Running Costs Calculator

Compare the annual energy cost of driving an EV versus a petrol car. Enter your mileage and efficiency figures to see the difference.

Reviewed by Richard Ross · Last updated April 2026

How EV vs Petrol Running Costs Calculator works

How the running cost comparison works

The calculator computes annual energy costs for each vehicle type separately. For the EV: total kWh needed = annual mileage ÷ miles per kWh. This is split between home charging (at your home tariff, default 24p/kWh) and public charging (default 65p/kWh). Weighted average cost per kWh is calculated from the home/public split. For petrol: litres needed = annual mileage ÷ (MPG × 0.21997 litres/mile conversion). Annual cost = litres × price per litre (default 140p/litre, current UK average). The saving is the difference between petrol and EV costs. A positive figure means the EV is cheaper to run.

What this calculator does not include

This comparison covers energy and fuel costs only. It does not include: depreciation (EVs typically have a higher purchase price), VED road tax (EVs now pay standard rate from year 2), insurance (broadly similar), servicing (EVs are significantly cheaper), home charger installation (£500-£1,200 one-off), or finance costs. For a complete comparison, use the True Cost of Ownership calculator which covers all these factors.

Worked example: 10,000 miles/year, 40 MPG petrol vs EV at 3.5 miles/kWh

Annual mileage: 10,000 miles. Home charging: 80%. Home tariff: 24p/kWh. Public tariff: 65p/kWh. Petrol MPG: 40. EV calculation: Total kWh = 10,000 ÷ 3.5 = 2,857 kWh. Home kWh = 2,857 × 80% = 2,286 kWh at 24p = £549. Public kWh = 2,857 × 20% = 571 kWh at 65p = £371. Total EV cost: £920/year (£77/month). Petrol calculation: Litres = 10,000 ÷ (40 MPG × 0.21997) = 1,136 litres at 140p = £1,591/year (£133/month). Annual saving with EV: £671. Monthly saving: £56. EV cost per mile: 9.2p. Petrol cost per mile: 15.9p.

Source: Ofgem — Electricity price cap (ofgem.gov.uk). RAC — Fuel prices (rac.co.uk/driving/advice/fuel-watch). DfT — Vehicle mileage statistics, National Travel Survey 2025.

Frequently asked questions

Is an electric car cheaper to run than petrol?

In almost all cases, yes. The energy cost per mile for an EV charged at home is typically 5-7p compared to 14-18p for a petrol car. Even with some public charging, EVs are roughly 50-60% cheaper to fuel. The savings increase with mileage.

Does this include VED and insurance?

No, this calculator compares energy/fuel costs only. For a complete comparison including VED, insurance, servicing, and depreciation, use the True Cost of Ownership calculator.

How much can I save per year switching to EV?

A driver covering 10,000 miles per year in a 40 MPG petrol car spending around £1,600 on fuel could reduce that to around £700 with an EV charged mostly at home — a saving of roughly £900 per year.

Are EVs still cheaper if I can only charge publicly?

Public charging at 65-79p per kWh significantly narrows the gap. An EV driver doing 100% public rapid charging may spend only marginally less than a petrol driver. Home charging is where the biggest savings come from.

Does this include the cost of installing a home charger?

No. A home EV charger (7kW wallbox) typically costs £500-£1,200 installed, reduced by the OZEV grant of up to £350 for eligible drivers. This is a one-off cost that you spread over your ownership period. On 10,000 miles per year, the charger pays for itself in fuel savings within 1-2 years.

What happens to the comparison if fuel prices change?

The calculator uses a fixed petrol price (140p/litre default). If you adjust this, you can model any scenario. When petrol prices spiked above 190p/litre in 2022, EV savings were approximately twice as large. At 120p/litre (a low scenario), savings are roughly 40% lower. The comparison always favours EVs unless public charging exceeds about 50p/kWh AND petrol is below 110p/litre simultaneously.

How does a PHEV compare to a full EV?

A PHEV (plug-in hybrid) with 30-40 miles of electric range can run on electricity for most short journeys, but uses petrol for longer trips. Drivers covering under 10,000 miles per year with regular home charging often see PHEV savings similar to a full EV. Above that, a full EV with adequate range typically saves more. This calculator models full EV vs petrol only.

What is the real-world efficiency of a typical EV?

Real-world efficiency varies from around 2.5 miles/kWh for large SUVs in cold weather to 5+ miles/kWh for efficient city EVs in summer. A good average figure for a family hatchback (e.g. Tesla Model 3, VW ID.3) is 3.5-4.0 miles/kWh. Motorway driving at 70 mph reduces efficiency to around 2.8-3.2 miles/kWh for most cars.

What tariff should I use for the home charging rate?

If you are on a standard tariff, use around 24p/kWh (the Ofgem cap rate as of April 2026). If you have an EV-specific tariff (Octopus Go, Intelligent Octopus), off-peak overnight rates of 7-9p/kWh apply — dramatically reducing home charging costs. Enter your actual overnight rate for the most accurate comparison.

How long does it take to break even on the higher purchase price of an EV?

EVs typically cost £3,000-£8,000 more than equivalent petrol cars (though this gap is narrowing). At £700/year in fuel savings, break-even on the purchase premium is 4-11 years. However, lower servicing costs (no oil changes, brake wear is reduced by regenerative braking) can shorten this to 3-7 years for higher-mileage drivers. Government grants and cheaper company car tax (2% BIK) further improve the economics.

These calculations are estimates based on 2026/27 HMRC and DVLA rates. Speak to a lender or qualified financial adviser for a personalised quote.