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0Solar roadways: Revolutionary concept meets engineering reality
- Updated: Oct 01, 2025
- 9 min
Edited by: Andrei Gorichenskii
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Highways that generate clean electricity while you drive, roads that light up with LED patterns to guide traffic, and surfaces that melt snow automatically... This was the captivating vision that made solar roadways go viral in 2014. The concept seemed almost too good to be true—and it was.
Solar roadways promised to transform ordinary roads into massive power plants. Instead of building separate solar installations, we'd simply replace asphalt with special solar road panels that could handle traffic while generating electricity. The idea captured imaginations worldwide and raised millions in funding.
Key takeaways
- Real-world solar roadway installations have consistently failed to meet performance expectations and prove cost-effective
- Technical challenges, including flat panel inefficiency, durability issues, and high costs, make solar roadways impractical with current technology
- Conventional solar panels installed alongside roads or on rooftops are 10-20 times more cost-effective than solar roadway systems
- Despite ongoing research, no viable large-scale solar roadway technology exists today
What are solar roadways?
Solar roadways are specially designed road surfaces embedded with photovoltaic panels that can generate electricity while supporting vehicle traffic. These systems typically consist of multiple layers: a bottom foundation, solar cells in the middle, and a transparent top surface strong enough to handle cars and trucks.
The concept goes beyond simple power generation. Advanced solar roadway designs promise integrated features like:
- LED lighting systems that replace painted road lines and provide dynamic traffic guidance
- Heating elements to melt snow and ice automatically
- Wireless charging capabilities for electric vehicles
- Smart road functionality, including real-time traffic monitoring and hazard warnings
Solar Roadways Inc. has raised approximately $4 million in total funding, but has never completed a functional roadway installation
The most famous company pursuing this technology is Solar Roadways Inc., founded in Idaho in 2006. Their viral 2014 video "Solar FREAKIN' Roadways!" garnered over 22 million views and helped raise $2.2 million through crowdfunding.
Other companies have also entered the space. French construction giant Colas developed WattWay technology, while various Chinese and Dutch companies have created their own versions. Each promises to revolutionize transportation infrastructure while generating clean energy.
The promise that captured the world
The theoretical potential of solar roadways seemed staggering. Solar Roadways Inc. claimed that covering just the contiguous United States road network with their panels could generate three times America's total annual electricity consumption.
The math was compelling. With approximately 4 million miles of roads in the US (about 2.3 million of which are paved), even modest efficiency rates could theoretically produce enormous amounts of clean energy. While these calculations ignored real-world limitations, they sparked global interest.
The company's marketing highlighted multiple benefits:
- Massive renewable energy generation using existing infrastructure
- Reduced need for separate power plants and transmission lines
- Safer roads with dynamic LED warning systems
- Elimination of snow removal costs through integrated heating
- Potential revenue streams from electricity sales
Government agencies took notice. The Federal Highway Administration awarded Solar Roadways multiple research grants totaling over $850,000. The company also secured contracts for demonstration projects, though most never materialized.
Real-world installations and results
However, when put to the test, these grand promises met harsh reality. Despite years of development and millions in funding, actual solar roadway installations tell a sobering story. Let's examine the major attempts and their outcomes.
France's WattWay project
France launched the world's first major solar roadway in December 2016. The 0.6-mile stretch in Normandy cost $5.2 million and used 2,800 WattWay photovoltaic panels covering the 1-kilometer stretch. Officials projected it would generate 300,000 kWh annually (790 kWh per day) – enough to power street lighting for the nearby town of Tourouvre.
The reality proved disappointing:
- Peak annual generation reached only 80,000 kWh (73% below projections)
- Road surface deteriorated rapidly from traffic and weather
- Panels created excessive noise, forcing speed limit reductions to 43 mph
- In May 2018, almost 10 percent of the roadway required demolition due to damage from heavy traffic, particularly tractors
The project officially ended in 2019 when WattWay's CEO admitted their system wasn't "mature enough for inter-urban traffic."
China's solar highway
China opened its solar highway in Jinan in late 2017, covering 0.6 miles with three-layer technology. Engineers claimed the installation could generate enough power for 800 homes annually.
The project faced immediate problems:
- Thieves stole panels within five days of opening
- Surrounding panels suffered damage during the theft
- Officials provided no performance data or updates after 2018
- Current operational status remains unclear
US installations
The United States has seen limited solar roadway deployment. A small installation in Peachtree Corners, Georgia, opened in 2020 using WattWay technology. This narrow strip within an autonomous vehicle test lane represents America's only operational solar roadway.
Solar Roadways Inc. completed just one installation: a 150-square-foot sidewalk section in Sandpoint, Idaho. This demonstration project immediately encountered problems, and in December 2018, Solar Roadways shut down the installation after operational issues emerged:
- Electrical system fire shortly after installation
- LED lights barely visible during daylight hours
- Failure to melt snow as promised
- Ongoing maintenance issues
Why solar roadways struggle
The gap between promise and reality stems from fundamental technical and economic challenges that current technology cannot overcome.
Technical challenges
- Flat panel inefficiency: Solar panels work best when angled toward the sun. Road-mounted panels lie flat, reducing efficiency by 30-40% compared to optimally tilted installations. This efficiency loss alone makes solar roadways economically questionable.
- Shading and debris problems: Vehicles create moving shadows that dramatically reduce power output. Even small amounts of shade can cut solar panel efficiency by 50% or more. Dirt, leaves, oil, and road debris further reduce light transmission to the solar cells.
- Durability requirements: Road surfaces must withstand enormous stresses from heavy vehicles while remaining transparent enough for solar generation. Current materials cannot meet both requirements effectively. The thick glass needed for durability reduces light transmission, while materials transparent enough for good solar efficiency cannot handle traffic loads.
- Heat management: Road-embedded panels cannot benefit from air circulation, causing them to run hotter than rooftop installations. For every degree Celsius above optimal temperature, solar panel efficiency drops by approximately 0.5%.
Economic reality
These technical problems create an even bigger issue: economics.The numbers simply don't work. Solar roadway installations cost 10-20 times more per kilowatt than conventional solar farms while producing significantly less electricity.
Consider these cost comparisons:
- Solar roadways: $15,000-30,000 per installed kW
- Utility-scale solar: $1,000-1,500 per installed kW
- Residential rooftop solar: $2,500-4,000 per installed kW
The LED lights in Solar Roadways' design would consume over 25% of the electricity generated by the panels, dramatically reducing net energy output.
The Idaho demonstration project cost $60,000 for 1.529 kW of capacity – roughly $39,240 per kilowatt. A conventional solar installation of equivalent capacity would cost approximately $3,800-5,300 (based on current residential rates of $2.50-3.50 per watt).
Maintenance costs compound the problem. Road-embedded systems require specialized equipment and procedures for repairs, while conventional solar panels can be serviced with standard tools and techniques.
Solar roadways vs conventional solar panels
When comparing solar roadways to conventional solar installations, the advantages of traditional systems become overwhelmingly clear.
Efficiency comparison:
- Conventional solar panels: 15-22% efficiency in optimal conditions
- Solar roadways: 5-10% efficiency due to flat mounting, shading, and debris
Installation flexibility:
- Conventional systems can utilize rooftops, unused land, and purpose-built solar farms
- Solar roadways require replacing existing functional infrastructure
- Rooftop solar adds no additional land use requirements
Maintenance accessibility:
- Standard solar panels are easily accessible for cleaning and repairs
- Road-embedded systems require traffic disruption and specialized equipment for service
The economic case for conventional solar continues strengthening. Utility-scale solar costs have dropped over 80% in the past decade, while residential installation costs have fallen by more than 60%. Meanwhile, solar roadway costs remain prohibitively high.
For property owners considering renewable energy options, rooftop solar offers proven technology with predictable returns. A typical residential solar system pays for itself in 6-10 years and continues generating savings for decades.
The future of solar roadways
Given these overwhelming advantages of conventional solar, what's next for solar roadways? Despite repeated setbacks, research into solar roadways continues. Some companies are exploring niche applications where the technology might prove viable:
- Parking lots and low-traffic areas where durability requirements are less demanding
- Specialized surfaces like airport taxiways with controlled vehicle types
- Pedestrian walkways and bike paths with minimal structural stress
However, the fundamental physics and economics haven't changed. Solar panels work best when optimally positioned and unobstructed – conditions impossible to achieve on active roadways.
The most promising developments involve installing conventional solar panels alongside roads rather than within them. Highway right-of-way often includes unused land perfect for solar installations. These "solar canopies" over parking areas or roadside solar farms can generate clean electricity without the technical challenges of road-embedded systems.
Current research focuses on improving materials and reducing costs, but breakthrough innovations would be needed to make solar roadways competitive with conventional alternatives. Until then, the dream of power-generating highways remains just that – a dream that captured imaginations but couldn't overcome the laws of physics and economics.
The lesson from solar roadways isn't that innovation should be discouraged, but that revolutionary claims require extraordinary evidence. Sometimes the most practical solution is also the most effective one.
Sergey Fedorov
Co-founder & CTO
Sergey has been running A1 SolarStore since 2017 with the main idea in mind – making going solar easier for everyone. Based on a thorough market research and his personal experience, he shares his ideas on both solar industry and management related topics
More articles from this authorIllustrator: Dasha Vasina
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