Car running costs: battery electric v petrol

The price of filling a car’s tank with fuel has started to fall from what have been eye-watering highs, while electricity prices are set to rise in October. A cost comparison between a battery electric vehicle (BEV) and a petrol equivalent seems useful for potential car buyers.

The prices of unleaded petrol and diesel at UK forecourts have been falling more quickly than at any other point in 2024, as RAC Fuel Watch analysis revealed on 23rd September.

As of 19th September, a litre of unleaded was being sold for 136.15p on average – down 5p since the start of September (141.26p) and almost 7p lower than a month previously (142.86p).

BEV charging costs

A recent What Car? Real-world assessment of BEV ranges provides a helpful guide to assessing BEV efficiencies and costs.

A home charger will see a BEV charged at 22.4p per kWh (the current electricity price cap) for anyone on a standard tariff. However, special overnight tariffs can be far cheaper; Octopus offers a rate of only 7p/kWh, although slightly higher than standard daytime charging can offset some of this gain.

According to What Car, drivers charging a Tesla Model 3 RWD exclusively at home, paying 22.4p per kWh, would spend roughly £508 on electricity every 10,000 miles. If all the charging was at a public supercharger, which can rise to 79p per kWh, the cost rockets to £1795. However, for anyone accessing the overnight 7p per charging rate, the cost would plummet to £167.

Petrol costs

Based on a petrol-powered BMW 320i, which is a close premium equivalent to a Tesla Model 3. The BMW has a claimed 42.80 MPG, using Fleet News’ Car Cost Calculator, 10,000 miles at the prevailing average of £136.15 per litre petrol costs would see 10,000 miles cost £1439.43. Use motorway service stations, and this jumps to £1701.52

‘Real world’ implications

The average annual mileage in the UK is 7,567 miles, according to the Department for Transport website.

Based on an analysis of MOT test data, over half of the vehicles in Great Britain travel less than 100 miles per week, with under 5% of cars driven over 15,000 miles per year by car, or 41 miles per day.

Based upon this car usage insight, the average UK motorist will have minimal reason to use a motorway service station for petrol or diesel. A BEV driver, provided they have a home charger, and since most of today’s BEVs have a range exceeding 200 miles, should be able to complete most of their charging requirements at home. Whether opting for a dedicated overnight tariff is worth the higher daily tariff would be an individual decision. For this reason, we have not included it in the final result, but it will be very viable for some.

Based on this process

• A Tesla Model 3 RWD exclusively at home paying 22.4p per kWh would spend roughly £508 on electricity every 10,000 miles. (This will rise a little in October when the cost cap increases)
• The BMW 320i, travelling 10,000 miles at the prevailing average of £136.15 per litre petrol costs, would see 10,000 miles cost £1439.43.

Indeed, there are plenty of caveats to this, and individual drivers must assess their driving usage and access to a home charger, but having used recognised third-party data sources, the potential difference, based just on ‘fuel’, is significant.