There is a wattage calculator online that has helped put into perspective the amount of wattage a typical rider experiences on a downhill. This calculator isn't eBike specific but it is something that can help people relate to how powerful an eBike is or can be. My attention span for physics is shorter then it needs to be to feel 100 percent confident in my interpretations, so feel free to correct me!
It appears that a descent on a 20 percent grade provides 2400 watts of assistance, and a descent of 30 percent provides 4500 watts of assistance.
https://www.gribble.org/cycling/power_v_speed.html
It appears that a descent on a 20 percent grade provides 2400 watts of assistance, and a descent of 30 percent provides 4500 watts of assistance.
https://www.gribble.org/cycling/power_v_speed.html