I'd like to add that there is some major handwaving about wattage in the ebike industry.
I explain, of course :
- The maximum wattage isn't really a technical limitation but a legal limitation
- customers want maximum power that fit the (legal) bill
- so we're in the very case of customer getting more than what's on the paper because "woaa that drivetrain is more powerful than that other one" even if, on the paper, they're both 250W
- there is no standardized method to determine the 250w legal limit
- sooo... most, if not all, manufacturer provide "continuous max power : 250w" that can be much much lower than the "peak power" (that could easily be 36v*20A=720W).
- while the torque number provided on paper are, indeed, max torque. (50-80NM in most case)
So, with that said, what now...
- You're on a hill, at max 50NM torque, with the engine running at 100RPM = 250w.
- Same hill, 50NM torque but at 200RPM = 500w
- more watt, you go faster at same torque.
Easy stuff in an ideal world. In reality it's a bit nightmareish because it's not linear at all. Plus add a few tons of torque and power limitation (eg : max current, heat, flawed/marketing rating, voltage drop, ...).
To be honest i don't even know if the 250w limitation is the energy consumption of the motor, or the work produced, which can be radically different : you block an engine (with whatever, brake, a wall, who care) and switch it ON, it will suck up the battery at whatever maximum Current (Amps) it can get, overheat, and so on, but effectively produce 0W of work since it will turn at 0RPM. Weird, huh ?