France spent roughly five million euros to surface one kilometer of road in Normandy with photovoltaic panels. The road, called the Wattway, opened in December 2016 as the first solar highway in the world, and a French government minister stood at the inauguration and talked about covering one mile of road in panels for every 621 miles in the country. The Wattway generated about half the electricity it was supposed to. The panels cracked and came loose. Rotting leaves buried the cells and cut the output further.<\/p>\n
Driving over the surface produced a noise that residents compared to a helicopter, and in May 2018 a 90-meter section had to be demolished outright because it was beyond repair. In the summer of 2024, eight years after the ribbon-cutting, a crew pulled the whole thing up and hauled it away. That is the actual track record of the technology behind a story that resurfaces every few months: that the United States, France, Germany, and Switzerland are paving highways with armored solar panels strong enough to carry trucks, and that soon the road under your tires will generate the power to charge your EV. The pitch has proven far more durable than the panels.<\/p>\n
When people say “solar road,” they mean one of two things, and the difference decides the entire question. The first is a road surface built from solar panels: photovoltaic cells embedded in a hardened, drive-over surface that replaces asphalt, with cars and trucks rolling directly across the glass. That is the Wattway, built by the French firm Colas. That is Solar Roadways, the Idaho project that raised millions in crowdfunding and federal grants, generated a fraction of its promised output, and was never properly traffic-tested. That is the version nearly every breathless article is describing, and it is the version that has failed almost everywhere it has been installed.<\/p>\n
The reasons are not complicated. A panel lying flat on the ground, the only orientation a road allows, captures far less sunlight than the same panel tilted toward the sun on a rack. It sits in the shade of every vehicle that passes over it and every leaf that lands on it. It has to survive 18-wheelers and farm tractors, which means burying the cells under a protective layer that cuts the light reaching them even further. And when the surface cracks, the repair bill covers a power plant and a traffic lane at the same time, in a live road.<\/p>\n
The second technology is solar built around roads instead of into them: canopies suspended over the lanes, arrays on the embankments and cuttings beside the pavement, and photovoltaic noise barriers that double as sound walls. That version works. It is scaling. And it has almost nothing in common with the first one except the word “road.”<\/p>\n
The German and Swiss projects that coverage lumps in with the Wattway are, with very few exceptions, the second kind. In Germany, the state-owned motorway operator Autobahn GmbH and the utility RWE are putting solar on the land alongside the Autobahn, not in it. A feasibility study by the engineering firm Drees & Sommer found that a 24-megawatt array along a 30-kilometer stretch of highway near the Garzweiler mine in North Rhine-Westphalia was legally, technically, and economically viable, on the embankments and noise barriers rather than the driving surface. The Fraunhofer Institute for Solar Energy Systems has estimated that Germany’s federal highways could host on the order of 54 gigawatts of photovoltaics, again, beside and above the lanes.<\/p>\n
Switzerland’s contributions are a 500-meter solar noise barrier on the A13 near Chur, generating around 30 megawatt-hours a year while cutting traffic noise for nearby residents, and a feasibility study for a 14-megawatt array built over a motorway in the canton of Fribourg. The most relevant German-Austrian-Swiss effort, a project called PV-S\u00dcD, built a photovoltaic canopy over a highway rest area on the A81 near Lake Constance. It is a roof over the road, generating power while shading the pavement underneath. The road stays asphalt. The solar goes on top.<\/p>\n
The U.S. drive-over experiments are real, tiny, and upfront about being experiments. The Ray, a nonprofit that runs an 18-mile stretch of Interstate 85 in Georgia as a testbed, installed 50 square meters of Wattway panels at a visitor center near the Alabama state line in 2016, then worked with the city of Peachtree Corners to put a short Wattway section in an autonomous-vehicle test lane. That Peachtree Corners installation produces a little over 1,300 kilowatt-hours a year, enough to feed a single Level 2 EV charger at city hall. The Georgia Department of Transportation’s own director of operations, John Hibbard, said it will be years before solar surfaces reach the state’s actual highways, if they ever do.<\/p>\n
The roadside version has a longer and quieter record. Oregon’s Solar Highway program put a 104-kilowatt array near the Interstate 5 and Interstate 205 interchange back in 2008, generating roughly 128,000 kilowatt-hours a year, about a hundred times what the Peachtree Corners drive-over lane manages, from panels nobody drives on. That ratio is the argument in a single line. If the goal is to make highway land produce power, the cheapest and most productive way to do it is to keep the cars off the panels. Roadside and over-road canopies also pair naturally with charging infrastructure, where the panels can be angled to actually catch the sun. That solar-canopy approach to EV charging, which we’ve covered before<\/a>, is the version of “the road charges your car” that holds up.<\/p>\n The appeal is obvious. The United States has roughly four million miles of public road, all of it already cleared, graded, and sitting in the sun. The fantasy of converting that dead surface into a national power plant is hard to let go of, which is why the story gets rewritten every year regardless of how the last attempt went. Dylan Ryan, a lecturer in mechanical and energy engineering at Edinburgh Napier University who has studied the numbers, has put it about as bluntly as an academic will: solar roads are likely to stay a niche source at best, and the performance gap between a solar highway and an ordinary array pointed at the sun is not going to close. Flat, shaded, trafficked glass does not get more efficient because the marketing improves.<\/p>\n Roadside and over-road solar is a legitimate, scaling technology, and Germany’s highway estimates alone are large enough to matter to a national grid. But the honest version of the 2026 story runs close to the reverse of the one in circulation. The drive-over solar road, the armored panel a truck rolls across, had its flagship test in France, and France just dug it up. The technology that works was never the road itself. It was everything around it.<\/p>\n","protected":false},"excerpt":{"rendered":" France spent roughly five million euros to surface one kilometer of road in Normandy with photovoltaic panels. The road, called … <\/p>\nWhy the idea keeps coming back<\/h2>\n