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I thought watts was watts when it came to such things, no?
For simplicity, restricted e-bikes will be electronically limited, as it's easier to measure voltage and current at the motor input than torque and angular velocity at the final drive. For that reason, drivetrain losses will make a BB powered e-bike slightly less powerful measured at the tyres than a hub powered one, but only by a few percent. They will all be velocity limited by reference to wheel speed so the slightly reduced power will only actually mean slower speed in conditions where more than 250W total power is needed, which means up hill. At worst, when speed has dropped so low that aero and rolling almost drop out of the equation and nearly all the power goes to lifting the weight against gravity, the speed drop will be directly proportional to the power drop.
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gbj_tester
withered_preacher
A friend is involved with this company: http://cyclingwithoutage.org/ He is in Neuchatel, a town that is mostly on a hill, thus he is looking at some powered assistance. He tells me that the location of an electric motor (front hub, rear hub, BB) makes a difference in the available power. I thought watts was watts when it came to such things, no? So three motors with exactly the same amount of torque and power will produce differently depending on location on the bike/trike?