Besides by-law limitations for street legal maximum 500W power, there are many engineering and safety reasons behind sizing a motor power on a bicycle– no matter if this is a factory made bicycle or a retrofit conversion project.
3000W, 1500W, 1000W, 750W motors are not street legal and are too powerful and heavy for bicycles. Typically we offer high power motor system for students or R&D projects, not electric bicycle applications. Putting a 4L engine on a Toyota Matrix is just a waste of money and resources. This engine will break the transmission shortly and the car does not provide a satisfactory drivability on small wheelbase and small tires.
250-500W is the optimum power you can expect a reasonable weight, speed, range, durability and safety on a bicycle. Knowing that an aerobic pedaling power by a regular cyclist is between 70W to 200W helps us understand 500W is like 5 people pedaling power.
You may read or see exciting reports or videos about 1000W to 6000W electric bikes, however this will not last long on those bikes. Biggest motor is not always the best.