The biggest problem with trying to directly power EVs with solar roofs

Adding more solar panels to the roof of an electric vehicle (EV) offers limited benefits, as the roof space is constrained. A solar array of around 400W on a 22 square foot area can only produce about 1.6kWh in four hours, equating to just 4 miles driven at the EPA's average consumption rate of 39kWh per 100 miles. Variable factors such as shade, cloudy weather, heat, and parking angles can further reduce solar output.

While larger arrays can be added, they introduce additional weight, which requires more energy from electric motors, and may compromise aerodynamics, increasing drag and reducing overall efficiency. Some automakers are exploring solutions like panels that can be retracted when the car is in use and light EVs designed for solar efficiency, but these approaches face practical challenges.

RVs with rooftop solar systems, like Winnebago's 210W setup on the Revel Sport, are more suitable for off-road use, as solar panels are not expected to contribute significantly to vehicle propulsion. Despite efforts to integrate solar power into EVs, such as Nissan's expandable solar panel prototype, the technology still struggles with weight, aerodynamics, and limited space.

Aptera, a company focusing on solar-friendly EV design, has achieved notable results with its teardrop-shaped, lightweight vehicle, delivering 4.23kWh of solar energy to its battery during tests, which could extend the car's range by about 42 miles under ideal conditions. However, real-world scenarios like garage parking, cloudy days, or long road trips would diminish these benefits.

Aptera's ambitious goal of achieving 100Wh per mile remains challenging, as evidenced by Lightyear's bankruptcy just weeks after launching its solar-powered EV.