A couple years ago, a handful of startups announced solar-powered cars they promised to bring to market soonish. “Solar-Powered Electric Vehicles are Almost Ready to Hit the Road,” headlined the Wall Street Journal in November 2021. One of them was so attractive that I put my own name on the waitlist.

Alas, aside from a few prototypes, solar EVs aren’t hitting any roads you or I actually drive on anytime soon. The would-be manufacturer of my dream car sunk into bankruptcy shortly after I signed up, and its would-be competitors aren’t faring much better. And no wonder: the whole idea of a solar-powered car rests on misunderstandings about the economics and technology of the energy transition.

Thinking Way Outside the Box

The solar-powered vehicle startups all claim the same value proposition: photovoltaic cells on their cars could keep their batteries charged and increase range to as much as 1,000 miles. Lightyear, the Netherlands-based company that caught my eye, said it would sell its 500-mile range Model 2 for under $40,000 — less than most EVs with no solar panels and far shorter ranges. It sounded too good to be true. And it was.

Solar panels are cheap these days, but they’re not free and they add weight and complexity to any vehicle they’re attached to. Despite manufacturers’ claims, and the tech media’s credulous acceptance of them, the panels don’t pay for themselves for a long time, even if you park your car in direct sunlight all day. Charging EVs using solar-generated electricity is a great idea, but it turns out that panels pay off quicker on the roof of your home or garage than on your car.

There are some promising alternatives. One example: employers can add solar-based charging to their parking facilities, allowing employees to top up EV batteries with off-peak workday solar energy that might otherwise go to waste (see below). The photovoltaic cells don’t even need to be co-located with the parking.

Nothing New Under the Sun

Like electric cars themselves, which date to the previous turn of the century, solar-powered vehicles are not a new thing. In 1987, the Sunraycer won the World Solar Challenge, running from Darwin in the north of Australia to Adelaide in the south. Funded by General Motors, the Sunraycer was developed by AeroVironment, led by Paul MacCready of Gossamer Albatross fame, with engineering support from Hughes Aircraft. The car weighed just 585 pounds, with most of that coming from the silver-oxide batteries; the frame weighed a mere 14 pounds (no misprint).

Sunraycer traveled the 1,867 miles at an average speed of 41.6 mph, finishing in 5.2 days, and a year later broke the solar-powered speed record topping out at 75.276 mph. GM sent the car on a promotional tour and its fame led directly to the GM Impact, also developed by Aerovironment — which in turn led to the GM EV-1, an experimental electric car that was leased to retail customers for a few years in the late 1990s before being unceremoniously scrapped. See: “Who Killed the Electric Car?”

College students around the world continue to build and race solar-powered cars, but while the Sunraycer and its descendants are long on proof of concept, they’re short on real-world applicability.

“The car that was driven across Australia was not the sort of car people expect to drive to work,” said Jenny Chase, an analyst with Bloomberg NEF. “These days you want your car to drive at least 200 miles [between charges], so it needs a big battery and it’s going to be quite heavy. You don’t necessarily want to leave it in the sun to charge for three days. What you absolutely can’t do is add weight because you’re going to actually reduce range.”

To Infinity and Beyond?

For sheer audacity, it’s hard to beat Lightyear, which announced its $265,000 Model 0 in June 2022. The 0 featured a series of curved solar panels on its roof and hood to complement a 60kWh battery pack for a claimed 388 miles of range — 44 miles of which would be derived directly from solar panels. In theory, customers with short commutes could go months without the need to plug in. But they wouldn’t get from here to there very fast: the Model 0 took a rather tepid 10 seconds to accelerate to 62mph from a full stop.

Lightyear said it would make 946 units of the Model 0, but only a handful were ever produced. The company said it was dropping production of the Model 0 to concentrate on the Model 2, then that it was seeking bankruptcy protection, and most recently that it had hired a new chief financial officer to sort things out. I’m not holding my breath.

Then there was the Sono Sion, a solar-powered minivan from Germany that promised 190 miles of range on a charge, and a retail price of $25,000. But even that relatively modest range wasn’t all from built-in solar. Sono said the sun could 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 — less than the average 41-mile American commute. Real-world solar range would vary with the weather. Sono tried crowdsourcing the Sion, but failed to raise sufficient funds and ceased development in February.

Still plugging away after 10 years is Aptera, whose sleek, 1,800-pound solar three-wheeler can be seen zipping around San Diego in prototype form. The Aptera Paradigm looks like the EV George Jetson would drive, and the company claims a zero to 62 mph time of 3.5 seconds, which is wicked quick. Aptera also claims up to 1,000 miles on a charge and up to 40 miles a day of solar-powered driving, but whether you’d want to share the road with mammoth SUVs is an open question. Fundraising, alas, has fallen short and production cars remain an aspiration. But if you want to dream the dream, Aptera is still offering the first 2,000 cars to folks willing to invest at least $10,000.

There are a few more modest (and realistic) alternatives. Toyota offers optional solar panels for its Prius hybrid, which it claims will provide about 776 sun-powered miles a year, displacing roughly 14 gallons of gas. Bloomberg estimated that at the peak of U.S. gasoline prices in June 2022, the roof would pay for itself in about eight years. You can also buy solar panels for Hyundai’s edgy Ioniq 5 EV, though they don’t currently show up on the company’s web configurator. Ditto for the panels Tesla has said it will offer on its long-promised Cybertruck.

Even when they are actually available, these options are not exactly game changers. “I think it’s a little psychological feature that potentially makes people feel better,” said Chase with Bloomberg NEF. “You can always carry a solar panel in your boot and put it on your roof when you park. But someone might nick it, and if you’re dragging that weight around, it’s going to affect your range.”

Trying to Make it Real

Let’s stipulate that EVs, though not without negative baggage of their own, are a positive step on the way to carbon neutrality. And let’s further stipulate that charging their batteries from renewable energy sources like solar is also a net positive. Even so, adding photovoltaics to EV body panels doesn’t look like a way to achieve these ends.

“There are constraints that we can’t get around,” explained Jessika Trancik, a professor at MIT, and creator of Carboncounter.com, a nifty site for comparing different automobiles’ carbon outputs. “Working within some of these constraints requires some pretty major efforts in areas like lightweighting and aerodynamics. Some of the companies are trying creative ways to get more solar panels on cars and reduce the mass and drag on the vehicles. But there’s still a lot of questions: will people want to purchase them?”

In a recent paper for the academic journal Cell Reports Physical Science, Trancik and colleagues make the case that the best way to power EVs with solar energy is to make workplace charging available. Employers and municipalities could add solar-powered chargers at parking facilities to take advantage of peak solar generation capacity that might otherwise go unused.

While electric vehicles figure in virtually all climate change mitigation scenarios, they point out, unmanaged deployment can raise electricity costs by increasing peak evening electricity demand and creating excess production capacity during midday. “Workplace charging can go a long way to allow vehicles to utilize solar energy, and from panels not necessarily located at the parking lot,” said Trancik. “If you want a solar powered car, I would focus more on the problem at that level.”

You Can’t Always Get What You Want

In April Elektrek, a site devoted to EV news, reported that Atlas Technologies, Lightyear’s parent company, was auctioning off the handful of Model 0 prototype cars it had produced, along with battery packs, motors and other bits.The auction has closed, but one can imagine an enterprising DIY enthusiast somewhere building something pretty cool.

The startup’s new incarnation is called Lightyear Technologies and has said it will go ahead with the Model 2. But the company is a shadow of its former self. Staff has been cut from 600 to 100, and creditors are still far from being made whole. And as Electrek reported, “Lightyear 2.0 has already stated it will need additional funding in order to deliver a solar EV that consumers can actually buy… and not through a fire sale.”