The issue of watts is murky; the rating is supposed to signify the maximum power that an electric motor can produce indefinitely, but at times it seems as though manufacturers designate a rating that suits their needs. My friend had a 2016 Bosch-equipped Felt (with a "350w" motor) that he modified by moving the magnet and sensor to the crank area and the bike was capable of 30+ mph. I've ridden two "500w" Stromers and both were capable of 30 mph for extended periods.