Electric vs conventional vehicle cost comparison | Running cost calculator

Assumptions and simplifications

The calculator above aims to help assess the running cost-saving potential of an EV. It makes various assumptions and simplifications to balance effort with accuracy. The default values are an example based on 03/02/2026 using an Octopus 12-month fixed tariff for the current tariff/standing charge (which is intended to be the tariff for electricity without an EV) and the Intelligent Octopus Go tariff for the EV tariff.

The reason general electricity usage is included in the calculations is that the day tariff for an EV tariff is generally marginally higher, meaning that although a car can be charged very inexpensively overnight, other hours for normal usage are more expensive, slightly reducing overall savings. It is assumed that all general electricity usage is during peak hours and all EV charging is during off-peak hours.

Other considerations

The cost of running EVs is well known to be lower than that of ICE vehicles, utilising diesel or petrol, due to their high efficiency. There are many variables to consider before making the switch, though. A switch to an electric vehicle requires a charger to be installed, where charging is to be done at home, which is typically installed for £949 or more. When long journeys are to be made, and charging is required at public chargers, this is almost universally at a premium; the higher the frequency of charging is required, the lower the benefit of an EV. On the present date, a typical 150kW+ charger would cost 82.52p/kWh compared to 7p/kWh for the example tariff used above. Presently, EVs are often more expensive to insure than traditional vehicles due to their inherent high performance, high cost and desirability, though this is likely to decrease as they become more dominant. Many new electric vehicles fall into the luxury car tax bracket, meaning that from years two to six of ownership an additional £425 is charged, which combined with standard road tax gives a total of £620. An equivalent value petrol or diesel car will pay more tax than this though due to the first year “showroom tax”.