An innovative coating containing solar power modules could transform the electric vehicle value proposition and ownership experience. By Will Girling
The convenience of electric vehicle (EV) charging—from wait times to availability and cost—remains one of automotive’s perennial challenges. EY Mobility’s 2024 Global Mobility Consumer Index found that 27% of those surveyed ranked lack of charging infrastructure as their biggest concern regarding EV ownership, more than any other single factor. The global EV charging market is growing quickly to address these concerns: valued at US$22.45bn in 2024, it could be worth US$257bn by 2032, according to Fortune Business Insights.
Mercedes-Benz recognises the importance and opportunity of solving the charging issue with novel technologies and production techniques. Jochen Schmid, Senior Manager of Future Electric Drive, tells Automotive World that his department generally focuses on the efficiency of e-motors, inverters, and batteries: “Charging is usually something that happens outside the vehicle.” However, his team is turning this idea on its head by focusing on how the car itself can be part of the equation.
On 22 November 2024, the automaker announced that it was collaborating with an unnamed partner to develop ‘solar paint’ that might eventually generate enough power to fuel the majority of drivers’ annual mileage for free.
Enlarging charging surface area
The concept of a solar-powered EV is not new, and dedicated start-up OEMs are making progress bringing their products to market. It should be noted, however, that examples like the Aptera use photovoltaic (PV) cells similar to the solar energy industry. “Standard solar cells are effective but have some limitations: the manufacturing processes are complex, the glass is bendable but brittle, and coverage is restricted,” Schmid states. Therefore, Mercedes-Benz is taking a different approach.
It started with a new kind of solar module, five micrometres thick and weighing 50g per square metre. As these cells were developed further, their efficiency gradually increased from 7% to 20%—roughly the same as standard PV and efficacious enough for automotive applications. By packing them into a wafer-thin layer of paste and spreading it at room temperature, Mercedes-Benz can utilise any area of the vehicle exterior that would traditionally be painted. “This enlarges the surface availability for solar charging far beyond just putting some PV cells in the roof,” says Schmid.
Although the new solution could broadly be described as paint, he explains that it has some important distinctions. “It’s not comparable to spray coating currently on production lines, and ovens aren’t used at any point.” There are also implications for EV construction: “All hang-on parts—doors, hoods, fenders, roof, etc.—need to be either thin sheet metal or moulded plastic. Until a very late stage, the car would look like a skeleton, and then all the outer parts with the solar paint applied would be clipped on.” At this point, the electric connection between panels and car is finally “realised”.
Harvesting sunlight
Mercedes-Benz claims that its solar paint is cheap to produce, easy to recycle, and contains no rare-earth elements or silicon. But despite creating an innovative method for increasing the surface area available for charging, the company still had a problem to solve. A string of six solar cells wired in series is 3V (0.5V each)—too low to be useful for an EV’s high-voltage (400V or 800V) battery. Using standard equipment to step up the voltage would require several phases, meaning added complexity and cost and reduced space in the vehicle to accommodate equipment.
The breakthrough came with a new power converter—a unit consisting of several micro-converters integrated directly with battery cells. Schmid describes it as “a ground-breaking technology that can boost low voltage to high voltage in one step.” Combined with the solar paint, the power converter enables each hang-on part to feed directly and efficiently into an EV’s high-voltage system.
In the real world, all sides of a vehicle will not be equally exposed to the sun, and light levels will naturally vary according to geography, season, and climate. Nevertheless, Schmid points out that most cars are parked outside for the majority of the day, presenting a regular opportunity to “harvest” enough light to make a tangible difference in the economics of EV ownership.
Assuming the vehicle in question was a popular mid-size SUV model—approximately ten to 13 metres of paintable surface area—he estimates that Mercedes-Benz’s solar paint could generate enough energy to drive around 12,000km (7,456 miles) per year in central European countries like Germany. This is only slightly less than the region’s average annual distance travelled per person: 12,540km, according to the European Automobile Manufacturer’s Association (ACEA). In sunnier locations, such as California, drivers could find more than 100% of their energy needs met, opening the opportunity for grid arbitrage through vehicle-to-grid (V2G) capabilities. Mercedes-Benz and other automakers are already exploring this idea.
The long road ahead
Using solar paint could have some practical implications for an EV’s colour, which might absorb or reflect more light depending on the shade. However, Schmid states that colour would not be achieved through ordinary paint pigment. “We use a coating containing nano particles that filters light wavelengths reaching the vehicle’s surface. To an observer, the car will appear whatever colour was chosen—anything from the colour spectrum, including black.” Importantly, this coating achieves 94% translucency, ensuring that the solar modules can still operate highly efficiently.
Having the paint is just the start; we need to develop an easy and affordable process for its application during series production
Although solar paint could prove revolutionary in terms of daily cost savings to customers and electric grid optimisation, he emphasises that incorporating all this innovative technology remains at the research phase. “Having the paint is just the start; we need to develop an easy and affordable process for its application during series production.” Throughout 2025, Mercedes-Benz will trial several potential approaches to determine the fastest and most economical. This will likely involve a lot of experimentation, as the solar modules must be tuned according to the geometry of the hang-on component to which they’re applied, as well as the power converter’s interaction with the battery.
The road ahead could be long, but Schmid is confident that solar paint will prove its worth. “I think it’s an understatement to say this might influence an EV purchase decision. With V2G capabilities, customers could choose to buy a car for their house’s solar power needs instead of putting PV panels on the roof.” In effect, buyers would own a “mobile power station” that also generated a large portion of their annual mileage for free, and business fleets would gain a lucrative source of extra income. “That could be the beginning of entirely new customer purchase behaviour and accelerate EV penetration tangibly,” he concludes.
