Public charging calculator guide

This guide provides details on how to use the Public Charging Calculator and the assumptions made when calculating time and cost to charge on the public charging network.

Selecting your vehicle

On the first screen you need to select your vehicle – both pure electric vehicles and plug-in hybrids are included on the list. 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. Once the vehicle has been selected you can look at the vehicle details.

Adding public charging details

On the input screen you are asked to select the speed of the public charger. You will only be shown charger speeds which are compatible with your selected vehicle and for which your selected vehicle is capable of charging at either with the standard or optional onboard charger. If you select a speed for which the onboard charger is not standard, you will be asked to confirm whether your vehicle is capable of charging at the higher speed.

The public charge costs defaults to an average per kWh pricing – you can edit this. If you are looking to calculate the cost of charging with a fixed cost, connection fee or monthly cost you can enter this cost in the Connection Fee section – it defaults to zero. The estimated real-world range for your selected vehicle is shown, if you, experience a different real-world range based on your driving patterns, you can enter your own figure.

The calculator will work out your public charging time and cost using the selected charger speed, costs, the battery capacity and the estimated real-world range. Even though there is a difference in speed achieved on a given charging point with different vehicles, it is assumed that charging speeds are 3kW, 7kW, 22kW, 43kW, 50kW, 120kW.

Your public charging results

Your charging time and cost for your vehicle are calculated using the data selected. As most people arrive at a public charging with some charge remaining in their battery and may not charge to 100%, you can vary the start and end % battery charge figures.

Rapid charger default end % charge has been set to 80% as many vehicle manufacturers recommend this as the limit for rapid charging. For most rapid chargers, charge speed tails off significantly between 80% and 100% battery charge, so if 100% is selected, this calculator will underestimate the charge time.

A worked example is shown below for the Nissan LEAF Tekna 30kWh.


Nissan LEAF Tekna 30kWh

Description Data
Electricity price (typical UK average) 45p/kWh
Manufacturer battery capacity (indicative)     30kWh
Official NEDC range 155 miles
Real-world range (estimated) 124 miles


Your charging time (hours)
Charging time (hours) = battery energy added (kWh) ÷ charger power (kW)
Example: 80% charge a Nissan LEAF 30kWh with a 50kW charging point
(30kWh * 80% ) ÷ 50kW = 29 minutes

Your charge cost (£)
Charge cost (£) = battery energy added (kWh) x electricity cost (p/kWh)
Example: 80% charge a Nissan LEAF 30kWh
30kWh * 80% * 45p/kWh = £10.80

kWh added
Battery energy added (kWh) = charger power (kW) x time (hours)
Example: 80% charge a Nissan LEAF 30kWh
30kWh * 80% = 24kWh

Cost per mile (p/mile)
Cost per mile (p/mile) = Charge cost ÷ miles added
Example: 80% charge a Nissan LEAF 30kWh
£10.80 ÷ 124 miles = 8.7p



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.

The cost per mile shown is for pure electric driving only. All calculations use independent data provided by the Zapmap database, based upon the manufacturer’s quoted indicative battery size (kWh), the public charger power (kW), the estimated real-world electric range figure and the price of electricity / connection fee / cost per charge.

You can change the range figure and electricity price to more closely reflect your experience. The real-world range figures are based on real-world driving tests or where this data is not available, estimated from official NEDC or WLTP figures (depending on model), 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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