The range is the most important metric for electric vehicles. The range tells you how far you can go on a single battery before you need to recharge or swap the battery.
In Europe range is stated according to a specific drive cycle called NEDC. This cycle was originally designed for petrol and diesel cars and is actually less suited for electric cars.
The real world range in an electric car is therefore most often different from the stated NEDC range.
As a rule of thumb the highway range for an electric car is about 60 % of the NEDC range. If the stated NEDC range is 200 km expect roughly 120 km on pure highway driving.
At slower speeds the real world range approache the NEDC range. However you should not expect to actually reach the NEDC range in everyday driving.
Examples of range have been given by Nissan (data from Wikipedia).
Electric cars are generally available with NEDC ranges anywhere from 90 to 425 km. The cost of the cars rises significantly with extended range, because batteries are so expensive. When selecting your range you should focus on your daily travel distance, from home to work etc. and the type of road you are going to use.
Use the range index in the table above to select the proper range.
Required NEDC range = 100 * Daily driving distance / Range index
For instance if your daily travel consist of 100 km highway driving, you should get a car with at least 159 km NEDC range. If you daily travel is 80 km city driving in freezing temperatures, get a car with at least 140 km NEDC range.