Electric Car Range: How is it affected by the Electric Motor wattage?

If the same car is moving at the same speed, it will use the same amount of energy to move it the same distance. (Weight difference between the motors will probably be negligible). The energy different motors use to supply this will vary

Assuming that both motors are rated high enough to maintain the desired speed, the biggest factor affecting range will be motor efficiency. The power rating has little to do with efficiency. It is possible that either the larger or the smaller motor could deliver the better range.

Generally electric motors with lower electrical resistance, better insulation, lower magnetic reluctance and smaller air gaps will have higher efficiencies. Running a motor closer to its voltage limits will mean less power losses. (Power losses=ampxampx resistance)

This link has some typical examples of motor efficiency curves versus output power.(EFF v Wo)

http://www.cyclone-tw.com/dc24.htm

Work out the power range that you car will need, to maintain your desired speed. Then you can then look for the motor with the best efficiency curves to match your needs.(and gearing).

In short it is more a matter of how well the motor is made and how well it matches your needs then what it is rated at. A larger motor will usually run more efficiently at its rated load. If it is running well below that then the smaller motor may well give best results.

The trade off for longer range is usually slower acceleration.