The directive says that the motor (when preheated) may not exceed a temperature rise of 25°C over a certain period of time, nothing else. I sure don't understand why all people talk about 250W. Its a myth.
My pedelec (bosch perfomance line CX motor) definitely peaks at over 1kW of power (plus my power), so for example uphill I have a combined power output of around 1500 W.