For the Maxun One solar bike I need a lightweight e-bike with a mid-drive motor and a total weight of about 12kg. Without motor assistance you may not feel any difference with a normal bicycle. There is no e-bike on the market that meets these requirements; therefore I have built a 12.5kg full-size touring e-bike myself, temporarily with a front hub motor. Homemade carbon parts, such as the battery case, drastically reduced the weight.
Test of the lightweight ebike
For cycling without the solar panels, a battery is used with a capacity of 360Wh (36V, 10Ah). On a flat road, there is no need for motor assistance at all; you can simply reach a speed of 30km/h. I use the motor only at uphill, during headwind, and at acceleration. The ebike has a large action radius: I drive through the South Limburg hills in the Netherlands more than 70km on just one battery. On a flat road, without actually pedalling, the speed is 28km/h.
The lightest e-bike
The 7.66kg e-bike Montanara Volta from Jean-Pierre Schiltknecht is the lightest e-bike. The middrive is built with an RC engine, which makes it lightweight and efficient.
Normal heavy electric bike
It seems that nothing is done to reduce the weight of a normal ebike which is often 28kg. Electric bikes are usually made for pensioners with saddle pain, who want to have comfort. So, ebikes are built like a Harley Davidson, high comfort and many accessories.
Velomobile en recumbent bicycle
Another approach to cycle with less power are velomobiles and recumbent bicycles. The solution is based on lowering the aerodynamic resistance. At climbing hills however, velomobiles and recumbent bicycles do not have advantages. Also the view around is hindered because of the low seating position.