I took a mountain bike and added an electric power to it. It works very well, has about 40 km range and will go 35 kph (faster than would be wise)

It is certainly practical for in town trips like going to work, weather and traffic permitting.

It was also not that expensive, something like $800 US for 1000 watt motor and 14Ah battery (If I recall correctly). There are many cheaper ones such as 250 watt motor but these are considered "pedal assist." Also in many places law limits bikes to 250 watts, to go higher you need a different registration.

Very interesting project. It led me to be less enthusiastic about the cars, though. It takes quite a bit of expensive batteries to move people around!