Let me tell you, since I have only access to an analogue bike, and no car at all, an e-bike is looking more and more like a it'll be life changing for me. We have some rental e-bikes in my town that I've used from time to time, but I don't like them as the designated parking spots is not ideal for my use case.
Access to an ebike will probably result in me taking significantly more trips with it, where I would otherwise have opted to either rent a car for an hour, or just not make the trip.
I don't have hard evidence to back up the claim, but I'm certain that an e-bike will rack up more than enough km's in a time period that the overall volume of ebike-exercise outweighs analogue-bike exercise, even if you subtract the "lost" exercise due to the e-bike assistance.
The amount of emotional and confidence boost you get from 250W of electricity honestly cannot be measured.