Can e-bikes speed up my commute? Which class? I have a daily 15 mile commute (1-way) which takes me approximately 1hr 15 min each way if I bike (taking into account traffic signals and so on). The route is all surface roads, with some mild hills. Sweating on the ride to work isn't an issue as my building has a shower and I don't feel particularly tired after. However, the sheer amount of time it takes each way is the main reason I don't bike every day; I'd like a commute that's more in the region of 45 minutes each way. I would like to cut my travel time. Therefore, I'm considering an e-bike purchase and am wondering the following:


Class 2 bikes go up to 20 mph with throttle and the saleswoman told me that pedal + motor could take it over 20mph. Is this true? On a Youtube video I watched they said something to the effect of "the motor stops helping after 20mph". Does that mean it shuts off once your speed goes over 20mph, leaving it entirely up to your muscle power?
Class 3 bikes go up to 28 mph per my understanding. Since I don't take bike paths on my commute they are legal (I live in California). Should I be considering a class 3 bike instead of a class 2 if my goal is a faster commute (as opposed to not sweating or getting tired)?


Based on comments, here is the question I'm actually trying to have answered:

Are class 2 bikes useful for going more than 20 mph consistently? Or is class 3 better for me if I want more speed?

Example class 2: https://electricbikereview.com/genze/sport-e101/

Example class 3: https://electricbikereview.com/juiced-bikes/oceancurrent/
Of course an ebike will be less effort and leave you less sweaty. And of course the faster the bike, the shorter the commute.

Class I: The key thing about this is that it's pedal assist only. The motor will only turn on while you're pedalling -- and it'll cut off at 20 mph -- so going faster than that will require you to pedal. Going downhill with a backwind and pedaling like a demon, you could feasibly go 40mph or faster.

Class II: These bikes have a throttle (combined usually with a pedal sensor) so the motor can turn on without pedaling. So you can go from 0 to 19.9mph without pedaling. At 20mph, regardless of whether you're using the throttle or pedal-assist, the motor will cut out and you'll have to pedal to go any faster or to maintain speed -- note that these bikes are usually heavy so even pedaling you're more than likely to quickly lose speed back down to 19.9mph unless you are pretty buff or you're going downhill. Technically, Class II  are limited to 20mph for electric assist but it's often possible to bypass that control with a firmware upgrade or setting in the control panel.  


  Speed Limiters: On most Class I and II bikes, the speed limiter is a hard cutoff. The motor can give you 100% power up until 19.9 mph and then when you hit 20.0 mph, the motor gives you 0% power and you have to pedal to maintain speed. The bike usually quickly loses speed (as pedaling a heavy bike at 20.0 mph is non-trivial) and the motor kicks back in at 19.9 mph. This can cause some jerkiness around the speed-limiter zone especially if you were using pedal-assist because the bike suddenly gets very heavy at 20 mph (it's not as noticeable with a throttle, where it just feels like the motor is cutting in and out).  More expensive bikes will more smoothly ramp the power down: 100% power at 19.0 mph; 80% power at 19.2 mph; 60% at 19.4; etc. etc. and then smoothly ramp the power back up while  you're accelerating. 


Class III: These bikes have a throttle (combined usually with a pedal sensor) so the motor can turn on without pedaling. These are limited to 28mph for electric assist but it's often possible to bypass that control with a firmware upgrade or setting in the control panel.  For example, some are sold with an "off-road only" switch. 

All of these are limited to 750 watts of electric assist power as well. For more info: https://electricbikereview.com/guides/electric-bike-classes/