Dear Collective of information.
Can anyone tell me if an electric motor say of 250 watts was geared to run almost always at speeds between its max power and max efficiency what would the effect be on its distance/longevity of use between charges. i.e. How much further would it run compared to a 'fixed' setup on one charge in % of distance terms?
Many thanks Jim

Are you in the EU? The reason I ask is because of the motor/power restrictions for street legal e-bikes in the EU and parts of Asia. Most e-bike enthusiasts in North America use conversion kits that have more powerful motors, although you'll find that many of the big manufacturers are putting 250W hub motors on all their e-bikes, including those destined for the North American market. You may get a more accurate answer to your question in an EU-based forum.

Like all vehicles, a number of variables will come into play with respect to how far someone will be able to travel on an e-bike. Clearly the less weight on the bike (smaller rider) the farther the bike will travel, but terrain and wind play a factor too. The larger the battery, the better. If the rider is willing to pedal, that augmentation of the battery will help significantly. If you don't pedal and you ride with the throttle at it's max, don't expect to go very far. Your speeds will also be limited by the motor's capacity, but that's what the EU wants--low-speed e-bikes.

My e-bike has a 450W Currie non-hub motor. I've got the OEM sealed lead acid battery (24V 10AH) and a new LIFEPO4 pack (24V 20AH) that I built fitted in the sides of the Currie rear mounted battery rack. I pedal and mainly use power assist for the steep hills (I'm in Montana, west of Glacier National Park so it's very mountainous). I've not gone on a really long trip with the new battery yet, but I still have had lots of power in the battery after 20 mile trips. I'm hoping to travel to a town that's 20 miles away and think I won't run out of battery power having both batteries to use. If our weather improves, I'm hoping to make that outing in a week or so. Good luck. Hopefully, someone with a 250W motor may chime in with more information for you.