Many factors affect the range of our bikes: the fitness of the rider, how good the surface of the road, how fast the bike is travelling, how strong the headwind, what load is being carried, how hard the tyres are inflated, how hilly the journey (though every hill climbed has its downside...).
We say an average rider contributing just half the effort required (with the motor supplying the other half) our standard 10AH battery will complete 30 miles before needing a charge.
If you ride the bike using a lot of throttle or using high assist settings then the range will be reduced.
If you ride in low assist mode and ride at a more gentle speed then you can expect an increased range.
For our smaller wheeled bikes, the 20" Urban for instance, you should expect more "rolling resistance" and so a reduced range - typically 24 miles in medium assist. Smaller wheels have to revolve more often to go the same distance and tend to be slowed by small lumps and bumps, unlike larger wheels which ride over more easily and have to turn less to go the same distance.
Juicy Bike have a range of upgrade batteries to increase your range.