Electric cars with rooftop solar are gaining popularity

BLOOMBERG

Egineering students from across the US compete in the American Solar Challenge, where around 10 schools cobble together a car designed to go as far as possible, powered exclusively by the sun. In 2022, the Massachusetts Institute of Technology (MIT) took the top prize with a car that looks sort of like a ping-pong table sprouted wheels. On its best day, the Nimbus made it an impressive 869 miles, roughly the distance from New York to Milwaukee. Of course, there are just a few impracticalities to contend with: The Nimbus can’t carry a passenger, for one, let alone a haul of groceries.
The quest to develop a solar-powered car that is at once functional, useful and practical has stumped more than the young wizards at MIT. In February, Sono Group NV said it would abandon its Sion solar-electric car after failing to raise enough money for the project. Dutch startup Lightyear suspended production of its $264,450 solar car and filed for bankruptcy. California’s Aptera Motors, while happy with its three-wheeled solar-powered machine, has struggled to complete a crowd-funding campaign to get it into production.
For about 40 years, car companies, startups and DIY enthusiasts have been pursuing the plug-less electric car, one that could wirelessly recharge via photons. But as logistical and economic hurdles continue to stymie those projects, the more immediate future of solar-powered vehicles is becoming clear: smaller, lighter, cheaper systems built to subtly augment electric driving, rather than power it in full.
The Hyundai Sonata isn’t particularly fast or large; it’s not even entirely electric. Cars don’t get much more milquetoast than this hybrid sedan, which has been around in some form since 1985 — except, that is, for the Sonata’s roof, which on newer models shimmers like fish scales. A closer look reveals that the roof is veined with a sheet of photovoltaic cells that casually, and very slowly, trickle about two miles of extra range a day into the car’s hybrid system, depending on cloud cover.
Toyota, too, sells a solar roof as an add-on option for its Prius hybrid. The company doesn’t expect many customers to spring for it, though those playing a very long game might be inclined to. The Prius panels make for about 776 sun-powered miles a year, or roughly 14 gallons of gas. At the peak of US gasoline prices in June, the roof would pay for itself in about eight years. Toyota says it’s now considering a similar system for the bZ4X, its new all-electric vehicle. Hyundai, meanwhile, is drawing up plans to add solar panels to the Ioniq 5, its breakout EV, which starts at $41,450.
Even Elon Musk is on board. The Tesla chief executive said — or, tweeted — that buyers of his long-promised Cybertruck will be able to add solar as an option, integrated into the cover of the pickup bed and possibly as unfolding “wings.” Musk has also said a car is one of the least efficient places to put solar.
He’s not wrong. For one thing, panels best capture photons when they are at a slight angle rather than parallel or perpendicular to the sky. And with an auto ecosystem increasingly wired for electrons — including charging infrastructure — on-car solar systems don’t have to do all the heavy lifting. Any EV can be “solar-powered” by plugging into an array of panels at home or a charger that is itself powered by solar energy.
To be sure, the cost-benefit analysis on small-scale solar installments has steadily improved as photovoltaic hardware becomes both cheaper and more efficient. Over the past decade, the price of solar modules per watt of power produced plunged by 78% to roughly 24 cents per watt, according to BloombergNEF — one major reason the amount of solar on homes and apartments has risen seven-fold in that time. At current rates, a panel array the size of the one on the Sonata has dropped from $222 to about $48. BloombergNEF expects the glut of cheap product to continue this year as another nine panel-makers hit the market, a 50% increase over the current crop.