Here’s something to chew on over the holiday break: The top of a car is wasted space. Sure, you can put a sunroof there to let in a little light and breeze or install a roof rack to take your surfboard to the beach. But for the most part, the roof is just a field of metal to keep the elements out of the cabin.
In an electric vehicle, that square footage could have a job. What if solar panels embedded in the roof generated juice to recharge the battery as the car flies down the highway or sits in the middle of a parking lot, blasted by the summertime sun? It’s an idea that’s starting to get more traction. It’s about time.
The idea of a car slathered in solar panels is well-worn territory. For decades, engineers have staged solar car races such as the World Solar Challenge, contested by vehicles running solely on sun power. It takes a lot of real estate to generate enough solar energy to move something as heavy as a car, though. That is why solar challenge competitors are often stripped-down, super-lightweight pods.
The question for a commercial car is, can embedded solar produce enough energy to make it worth the trouble and expense? A few, like the Lightyear One concept vehicle, have dared to try. Aptera keeps trying to sell the solar car. Among real production EVs, the doomed Fisker Ocean offered a solar roof on its most expensive version. Toyota’s Prius Prime plug-in hybrid offers a solar roof as an add-on. In some places around the world, the popular Hyundai Ioniq 5 comes with enough solar capability to add 3 miles of range per day.
EV solar hasn’t caught on in the mainstream, however. The world’s top EV maker, Tesla, has long been standoffish about the idea. When CEO Elon Musk is asked about EVs with solar, as he was on the Joe Rogan Experience podcast in 2023, he typically dismisses the idea. After Rogan pressed him, Musk estimated that a square meter of PV would be exposed to just 1 kilowatt of energy and could probably only harvest 25% of that, a tiny contribution that’s nowhere near what you’d need to push a Tesla down the road. (Modern DC fast-chargers discharge energy in the hundreds of kilowatts.)
In other words, what solar panels on a car could harvest amounts to a drop in the bucket. But if you leave out enough buckets for long enough, those drops eventually add up to something. For example: At the same time he was pooh-poohing car solar, Musk acknowledged the promise of a kind of fold-out system, something that unfurled like a satellite to expose a large surface area of PV. Imagine those backcountry panels you can fold out at a campsite to harvest solar power for charging your phone, scaled up.
Los Angeles-based DartSolar is trying to sell just that. The startup has begun offering a package of solar panels that can sit on the roof of an EV just like that big Thule roof box riding on the top racks of so many Subarus. When closed, just two of the six available solar panels are exposed, gathering up to 320 watts of energy as the car drives or sits in an outdoor parking stall. Find yourself at a campground, the beach, or anywhere else there’s room for the package to expand, then all six panels can start generating electricity at a maximum of 960 watts, or nearly a kilowatt.
The company claims that you could add 10 to 20 miles of driving range per day this way, which is nothing to sneeze at. It’s like a green range extender that just lives on top of your car and, at 87 pounds, doesn’t weigh so much that it’s killing your mileage. But it’s not exactly cheap: DartSolar says the package will ultimately cost around $3,500, meaning it would take quite a while to recoup the upfront from free solar energy, even if the system does qualify for some incentives.
Another startup, GoSun, offers a slightly different take on the same idea. Instead of expanding into a flat plane of PV, its panels cascade from the roof down the front and back to gather up to 30 miles of range per day. GoSun promises to deliver in 2025 for about $3,000.
Of course, the smartest way to power your EV with solar is to put PV on the roof of your home, a place with much fewer square footage and weight constraints than the surface of a vehicle. But as solar continues to get more efficient, it will make less and less sense to ignore the real estate on a car. After all, every watt of extra energy from the sun is one you don’t have to get somewhere else.
Courtesy of U.S. Forest Service
