Journey Cost Calculator guide

Below are some details on how to use the Journey Cost Calculator and the assumptions made when calculating your journey costs.

Selecting your vehicle

On the first screen you need to select your vehicles for comparison. Firstly choose a pure electric vehicles or plug-in vehicle, the default shows you new cars that are available to buy now, but you can also select the Used button to find any plug-in car which has been on sale in the UK. Next select your comparison vehicle, this can be another plug-in vehicle or a petrol / diesel car.

Adding your journey details

On the input screen you are asked to provide details about your journey distance – you can either enter a mileage value or, using the Plan a route option, enter the start and destination of a typical journey and the tool will calculate the distance. The default journey frequency is daily, but you can change to monthly or annually as desired.

The home electricity cost, which will be used to calculate your electricity costs, defaults to the UK average. Source: UK Government – updated annually. You can edit and change to your own tariff if you wish.

If you have chosen a petrol, diesel, hybrid or plug-in hybrid you will also be able to change the default cost per litre. The default shows the UK average from petrol prices Petrol Prices and is updated monthly.

Your journey cost results

Your journey costs using the two vehicles selected are calculated using the vehicle, distance and fuel price data selected or entered via the mapping tool. The results are displayed in three ways together with a cost comparison over a year:

1. Journey fuel costs = fuel economy x miles x fuel price. Results are rounded to the nearest whole £pound.

2. Cost per mile = fuel economy x fuel price. Results expressed in pence per mile.

3. Total annual fuel costs = fuel economy x miles x fuel price x journeys per year.
Results are rounded to the nearest whole £pound.

More details on fuel economy calculations by vehicle type

A vehicle’s fuel cost is calculated by multiplying its fuel economy (using units of litres or kWh per 100 km) by fuel price (in pence per litre or kWh) and the distance driven (in kilometres). Inputs and results are shown in imperial units (miles-per-gallon, pence per mile and miles) using appropriate conversion factors.

The calculator, which can be used for all vehicle types (petrol, diesel and plug-in vehicles), provides results based on official NEDC data only.

Electric vehicles
For vehicles powered solely by electricity, fuel cost is calculated by multiplying the fuel economy (in kWh per 100 km) by fuel price (in pence per kWh) and the distance driven (in kilometres or miles). The real-world electric cost is calculated using real-world driving tests, or where not available, estimated from official NEDC test figures for fuel economy.

Plug-in hybrid vehicles
For plug-in hybrid vehicles powered by electricity and petrol or diesel, fuel cost for both fuels is calculated multiplying the fuel economy (in litres and kWh per 100 km) by fuel price (in pence per litre and kWh) and the distance driven (in kilometres or miles). The fuel cost is estimated using the assumption that the vehicle is driven for half the distance in electric-only mode and half using a conventional fuel (‘Condition B’); Real-world figures are used for both figures.

Petrol and Diesel vehicles
For vehicles solely powered by petrol or diesel, fuel cost is calculated by multiplying the fuel economy (in litres per 100 km) by fuel price (in pence per litre) and the distance driven (in kilometres or miles). The real-world fuel cost is from real-world driving tests or where not available estimated from test-derived figures (‘official combined’) for fuel economy as published by the NEDC.

Worked examples

Electric: Nissan LEAF Tekna 30 kWh

DescriptionImperial
Official energy use15.0 kWh/100km
Real-world energy use18.8 kWh/100km
Electricity price (typical UK average)14.0 p/kWh
Distance travelled (1 mile = 1.61 km)161 km100 miles
Real-world journey cost = (18.8 x 1.61 x 14.0 x 100)/100 x 100) = £4.24

Plug-in Hybrid: VW Golf 1.4 TSI GTE 204PS BMT DSG

DescriptionImperial
Real-world Fuel Only fuel economy7.1 litres/100km39.8 MPG
Real-world energy use14.2 kWh/100km
Petrol price (typical UK average)120.4 p/litre
Distance travelled (1 mile = 1.61km)161 km100 miles
Real-world journey cost = 0.5 * (14.2 x 1.61 x 14.0 x 100)/ (100 x 100) + 0.5* (7.1 x 1.61 x 118.3 x 100)/ (100 x 100) = £8.48

Diesel: BMW 3 Series 316d SE – Diesel, 1995cc

DescriptionImperial
Official combined fuel economy4.7 litres/100km60.6 MPG
Real-world combined fuel economy5.9 litres/100km47.4 MPG/100km
Diesel price (typical UK average)123.1 p/litre
Distance travelled (1 mile = 1.61km)161 km100 miles
Real-world journey cost = (5.9 x 1.61 x 123.1 x 100)/100 x 100) = £11.69

Notes

All results are based upon the theoretical optimum operating efficiency of the vehicle as quoted by the manufacturer. Please bear in mind that you may achieve very different results in real life. These tools should be used for comparative purposes only.

You can change the fuel cost figure to more closely reflect your experience. The real-world fuel economy figures are based on real-world driving tests or where this data is not available, estimated from official NEDC Figures, which are obtained from the official EU test data. These figures are intended for comparisons between vehicles and may not reflect real driving results.

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