Power assist factor?

Can someone explain power assist factor? I see many ebike & motor manufactures throwing these numbers around, but I'm not sure what they mean.

If some states a power assist factor of 1.15, what does that mean?



Well-Known Member
I think generally it is a factor of the watts the motor will put out in relation to rider input (at least for torque based systems). It could also be watt based - really they are kind of meaningless, and just really a scale against the power output of the motor itself (as opposed to a measure against other motors).

George S.

Well-Known Member
The Europeans take this stuff very seriously, specifying assist levels with precision.

Average rider goes around 12 mph, puts out 100 watts. A 1.15 assist level would add 115 watts, so the bike would use 215 watts and go more like 16 mph.

With a 2x assist level the total watts would be around 300 and the rider could go 20 mph.

Top assist levels might be 3x for Euro stuff, and that gets the 100 watt rider to maybe 23 mph. You need a lot of watts, as you get into the 20's.

US allows clown or play pedals. Turn the pedals, get full power.

Power has to be measured, probably at the crank, so fairly sophisticated stuff.


@ George, and a little off topic

It's amazing how fast wind resistance increases with speed, and how much power it takes to overcome it.

I guess I fit right in with your average rider as I average 12-15 MPH on the level, between 100-200 watts. I don't (95% of the time) use my assist (or throttle) to go faster that, but I don't slow down with wind gusts, or hills. I wanted my E-bike to extend my range, and help on hills. I's working out great, just as I had expected / hoped. With this type of riding I do get the range as claimed, so far 57 KM, with some left in the tank, probably not much though.

Haven't tried, but quite sure if I went at max power the range would be considerably less.