It’s basically impossible. Unpowered hub motors drag a lot. Unpowered mid-drives are better because they have clutches or freewheels, but you’re still pedaling a fifty-pound bike. Some ebikes do have regeneration triggered by brake lever switches but it’s pretty rare. Others have a regeneration mode switch. Most just don’t bother.

What you should understand about these bikes is the power delivered by the motor, and the power needed to recharge batteries in a useful time frame, greatly exceeds the continuous power a human would normally exert on the pedals.

Not sure I agree with that. It really depends on both the rider and bike. You can get a lighter weight (obviously with less range/power) mid-drive e-bike that is still manageable unpowered if you're not a small rider. It certainly isn't fun, but I've done it just fine on mostly-level ground with a sub-40lb bike.

Note that I have fond memories of pedalling girls around on the back of my unassisted bike back in the day, so I might not be an average rider.

It depends on the bike and on your condition. A normal cheap road bike weighs about 12 kg and an e-bike 22-24 kg. So riding the e-bike without e-assist is like riding a normal bike while being 10kg overweight (20 pounds maybe?) or like loading a bike with 10kg of cargo. It's doable, but is a lot heavier.

But there are also top of line electrified road bikes which are almost (almost!) like the road bikes they use in Tour de France but with an engine strapped onto them. They weigh about 11-13 kg and you'd have no trouble riding them without the assist. Of course those aren't cheap...

40 mile trips (60km?) are doable on e-bikes, but you'd have to conserve the battery. Like turning off the assist on flat terrain and only using it for riding uphill. Since you have a display indicating how much charge there's left you won't all of a sudden run out of power.

This is why I think the moped is in practice the better choice until this tech matures. Over 100mpg isn't bad, won't leave you stranded, and isn't as much of a magnet for theft.

I did see an ad for some electric moped with removable batteries. You simply pull up to a gas station and swap your empties for charged ones, just like propane tanks. No waiting on a charger, but it would require total adoption like gasoline did for it to be practical.

It is heavy and difficult. Regenerative braking is rare. The GeoOrbital Wheel (which converts a regular bike to an electric bike by swapping out the front wheel) does charge the battery when you're not using the throttle.

Why not use both? E-bike for commuting and regular bike for fun? Or why not get a spare battery to carry on long rides just in case?

I have a giant quick e+ and it has the gears to ride it without the motor, but it really sucks. I did a ride where I exhausted the battery and it sucked the last couple of miles. It's a 50 pound bike once the motor dies.

I have a middrive (BBS02) on a mountain bike and it absolutely sucks with a dead battery. You're not going to pedal much faster than 10MPH and it will be with decent effort unless you regularly cycle for exercise.