Used to take 45-55mins on a speed pedelec (45km/h) but I sold it and bought a regular ebike set at the US speed limit of 32 km/h. Depending on wind it takes me 60 to 70 minutes for 28.7 km.
I do ~15 km in ~31 minutes on an ebike. About ~1/3rd of the time is spent sitting at stoplights, as measured by Strava (18 minutes moving time, 31 minutes total time).
14 km/40 minutes is 21 km/h. Assuming you don't live in hilly terrain, if you use an e-bike with a 25 km/h limiter, you can probably go a little faster, but it won't make huge difference.
It will probably will mean that you get less tired and exercise less, which may be good or bad depending on your opinion.