A bicycle is fitted with rear panniers that provide electric motor assist and a power supply for the bicycle when desired. In a preferred embodiment the bicycle has a power coupling permanently attached at the rear wheel, for receiving an output drive shaft or power coupling from the motor pannier when that pannier is installed. The drive coupling may have gear reduction. To accommodate relative up and down motion between the pannier-supporting rack and the rear tire in a rear suspension bicycle, the motor drive unit in the motor pannier articulates, or the final drive unit on the bicycle can articulate, but this is more difficult because the rear suspension motion can be complex. Both panniers are secured by a quick connect device, for both mechanical attachment and electrical connection. The bicycle functions as a normal unpowered bike when the panniers are removed.