A self-built solar cargo e-bike has completed an ambitious 1,300-kilometer ride across France and the Alps, offering a practical look at how far sunlight can extend electric mobility.
British filmmaker and photographer Shawn Ryan joined the 2026 Sun Trip with a 61-kilogram cargo bike fitted with 200 watts of solar panels and a 250-watt motor. The route tested the bike's endurance over mountain passes, changing weather, and long days on the road.
How the system performed
Ryan's setup used a boost controller to convert the panels' variable output into usable charging power for two 36-volt batteries. On favorable days, the bike could move using only solar energy. In the UK, he measured consumption at roughly 10-12 Wh per mile, while panel output typically ranged between 70 and 100 watts depending on sunlight and angle.
During one demanding mountain day, the bike covered 130 kilometers and delivered nearly 985 Wh of usable solar energy to the electrical system. The average speed stayed around 21-22 km/h, showing that the concept can work efficiently when conditions cooperate.
Engineering limits in real terrain
The journey also highlighted the challenges of solar cycling. Heat, steep climbs, and limited panel area pushed the system close to its limits. One battery overheated during a French heatwave, and the motor had to be cooled on long Alpine ascents. Ryan also found that the bike performed best when the motor spun faster in a lower gear rather than under heavy strain.
Because of those conditions, he used grid electricity twice, adding about 1 kWh in total. That ended his eligibility for the solar-only competition, but not the wider experiment.
The ride suggests that solar e-bikes are especially promising for long-distance touring, where riders can spend hours harvesting energy away from charging infrastructure. Ryan is now looking ahead to a 2028 Sun Trip route from France to China, where a larger, more aerodynamic design could help expand the role of solar mobility. The next chapter may shape how future adventure bikes balance design, energy, and freedom on the open road.
