How the range is calculated
Range in miles is the usable battery energy in kWh multiplied by the car's efficiency in miles per kWh. A winter reduction takes a percentage off the result. An example 60 kWh battery at 3.5 mi/kWh gives about 210 miles from 100%. The same car gives about 168 miles from 80%.
Where to find your miles per kWh
Your trip computer shows a real figure from your own driving. That figure is the best input. A manufacturer's official energy consumption is often quoted in Wh/km. Divide 621.4 by a Wh/km figure to get miles per kWh. The calculator has a converter for this. An example of 160 Wh/km is 3.88 mi/kWh. The arithmetic uses 0.6214 miles in a kilometre and 1,000 Wh in a kWh.
Example ranges
These rows use the calculator's three example efficiencies. They are round-number assumptions and not sourced figures for any named car. The reduction columns show what a 10%, 20% or 30% cut would do. They do not predict how much any car loses.
| Example | Usable kWh | mi/kWh | From 100% | From 80% | 10% cut | 20% cut | 30% cut |
|---|---|---|---|---|---|---|---|
| Small battery, small car | 40 | 4.0 | 160 | 128 | 144 | 128 | 112 |
| Mid battery, family car | 60 | 3.5 | 210 | 168 | 189 | 168 | 147 |
| Large battery, large SUV | 80 | 3.0 | 240 | 192 | 216 | 192 | 168 |
Winter range
Cold weather and cabin heating both use energy. Range falls as a result. The size of the fall depends on the car and the day. The calculator takes your own percentage for that reason. The American Automobile Association's 2019 test of five electric cars found an average 41% reduction at 20 degrees Fahrenheit (about minus 7 degrees Celsius) with the heater running. That is a US laboratory result. Treat it as an example of the size of the effect and not as a UK figure.
Next: cost and charging time
The EV charging cost calculator shows the cost per mile and per year. The charging time calculator shows how long a charge takes. The journey planner estimates the stops on a trip longer than one charge.