German carmaker Sono says its Sion solar electric car will be coming to the US, prompting a lot of questions about what solar cars can do. I checked out a Sion in person during its first US tour and found that the answers are more nuanced than with a big-battery Tesla or a Hyundai Ioniq5 that has trivial solar charging. 

Range and where it comes from

The Sion promises 190 miles of range on a charge, but that isn't all solar range: The sun can account for about 5,400 miles a year, which averages out to 70 to 150 miles per week or 10 to 20 miles a day. That's less than many Americans drive and even that amount of solar range wouldn't be evenly distributed across all days because of weather, seasonality and where you park, the solar car equivalent of carefully siting rooftop solar for viability. When the car comes to the US it will have a solar position feature in its app to predict the amount of charge you'll get in a given parking space.

For most drivers, solar will be a free, completely green contributor to conventional plug-in charging, not an obviation of it. However, if you drive only very local trips -- or dedicate this car to them while using another car for longer driving -- this car could have a profound role in your transportation footprint.

How the Sion works

The Sion is plastered in solar panels, not just on the roof as a few other cars already have, but also on the hood and the car's sides. The solar panels aren't slapped onto existing metal bodywork but integrated into its dentproof polymer body panels. As a result, the car can't have a shiny paint job or range of colors, but Sono says production models will at least be an even shade of matte-gray-black, which happens to be a fashionable look these days.