Mine is a 250W mid-drive rated for 90Nm peak torque. I've documented several rides on this forum up the steepest local road; 31% (17°) grade as posted by the local road dept. We've driven out to measure this grade and confirmed the signage.I have a 750 watt hub motor with 48 volts 17 amp hr bat. I have to go up very steep hills in my neighborhood. I am 6ft 200 lbs. This bike screams going up hills. You should never have to walk your EBike unless your battery is dead.
Note that the 250W rating is often for Euro compliance and as I understand it is the max power the motor can continuously deliver under max operating temps without thermal overload. My ebike has torque sensing that reports rider and motor torque. Up steep grades the motor can develop a full 1hp (~750W). It has never cut out due to thermal overload, even on grades that went on for several miles.
For the record, I'm in my 70s and have 1 artificial knee and 1 'bad' knee. Haven't found a hill I've had to walk yet.
The bike has a 600Wh/17Ah rated battery, which is more a measure of how far I can ride, rather then motor capability.