Car shoppers soon may have another option to consider when buying — whether or not to add solar.

While vehicles powered entirely by the sun won’t be sold for a long time, if ever, a growing number of solar hybrids are on their way to showrooms. Though vehicles marketed with solar options so far have added little power at prohibitive cost, a number of manufacturers — startups and auto giants — see potential in the technology and are working on models that include solar. 

Even so, advances in panel technology and lower costs are needed before solar-powered cars and trucks are a common sight.

Early designs built the solar cells in the roof, while more recent offerings include solar modules on a car’s bodywork. A German solar research institute, the Fraunhofer Institute for Solar Energy Systems, has created a solar car roof which could provide electricity for a car to travel about 6 miles a day. It was displayed at the Frankfurt Motor Show this month. The roof can be coated any color and the cells are integrated invisibly into the structure. 

Two European startups are gearing up to start delivering vehicles that use solar power along with electric batteries. One is aiming for the luxury market, while the other is looking to launch a mass market car.

In June, Dutch company Lightyear introduced its prototype, the Lightyear One, which has a roof and hood covered in solar cells. The car can travel as much as 7.5 miles a day powered by solar. Lightyear claims that drivers in the overcast Netherlands traveling about 12,400 miles a year would obtain about 40% of their mileage from the panels.

“Our mission is to drive a lightyear’s worth of solar kilometers on sustainable energy by 2035,” Lex Hoefsloot, Lightyear’s CEO, told Karma. “Ultimately, we want to make clean energy affordable for everyone, everywhere.”

The Lightyear One doesn’t come cheap. The price tag is $164,000, with delivery in 2021. The company is looking to expand with lower-priced models and eventually wants to sell cars in the Third World where sun is plentiful and the electric grid spotty.

Meanwhile, Sono Motors has designed Sion, with 248 solar cells fused to the vehicle’s roof and body. The Munich-based company claims that the panels provide enough electricity in cloudy Germany to drive as much as 21 miles a day, and the car has a total range of 250 miles a day. Sono, founded three years ago, plans to start assembling the vehicle next year at the former Saab factory in Trollhattan, Sweden. 

“With the Sion as a platform our founders wanted to tackle three obstacles regarding e-mobility: range, price and infrastructure,” Sion spokeswoman Alexa Rauscher told Karma.

Sono is aiming for the mass market with Sion, and it can be preordered for $28,115. The strategy seems to be working — Rauscher said the company hit 10,000 orders in May and more are coming in.

Karma Revero

Karma Automotive, a luxury hybrid car maker based in Irvine, California, added a solar roof to its Revero model, which had a starting price of $130,000. The last Revero was recently delivered, and the company is retooling for the next generation Revero GT, coming later this year. Solar panels charge the car’s battery, increasing its range. Karma is owned by Chinese automotive-parts company Wanxiang Group.

Toyota, Nissan, Hyundai and Audi have offered vehicles with solar panels, but Audi and Nissan dropped the option because it elicited little interest. The panels only provided a token amount of power that didn’t justify higher prices. Toyota and Hyundai haven’t given up on solar, and Tesla may be joining them.

It’s been two decades since Toyota introduced the Prius, bringing car hybrid technology to the mass market. The company is looking to maintain its technological lead by being in the forefront of bringing solar vehicles to the market. Toyota is selling a Prius in Japan that has solar panels as an option. However, the vehicle only charges when parked and the panels only provide enough power for driving about 4 miles. 

Toyota is working with Sharp Corp. and the New Energy and Industrial Technology Development Organization of Japan to develop a new solar Prius. As part of the effort, Toyota began testing an advanced solar-electric hybrid in July. The car is equipped with solar films developed by Sharp that are about 0.001 inches thick. The thinness means they can be applied to the roof, hood or hatchback.

If the new Prius is driven four days a week for a maximum of 31 miles a day, there will be no need for the car to be plugged in, Mitsuhiro Yamazaki, director at the solar energy systems division of NEDO, told Bloomberg earlier this month.

Hyundai launched a car with a solar roof called the Sonata Hybrid last month. Silicon solar panels attached to the roof charge the battery while the car is moving. The technology will be offered on other vehicles in coming years, Hyundai said. The company claims that between 30% to 60% of the car’s battery could be charged using the technology. The car is for sale in South Korea and the company says it will soon be sold in North America.

Tesla Absent

One company that hasn’t joined the race to use solar is electric car pioneer Tesla. The company hasn’t followed through on CEO Elon Musk’s 2016 tweet that he’d like to offer a solar option to the Model 3. At a forum in July 2017, Musk said that solar panels on vehicles are “not that helpful, because the external surface of the car is not that much. The least efficient place to put solar is on the car.”

A big impediment so far, as Musk made clear, is that solar panels need a lot of surface area to be effective, although improvements are being made in this area. A solar vehicle also needs a battery with enough capacity to run during dark hours. 

As solar panels get thinner and more efficient, and batteries improve, solar power may become a popular option for drivers. The technology may become common in large trucks before it’s seen in many cars and vans, because commercial trucks have a larger roof surface, offering greater savings. Electric trucks with a solar roof can travel 3,100 miles a year on electricity generated by rooftop panels, according to a Fraunhofer study.

Solar technology may curb pressure on the electric grid as the number of hybrid vehicles on the road multiplies. Charging stations with large surface area would collect a great deal of power that cars and trucks could access when they plug in. 

While an automobile solely powered by solar might not be on the market soon, there is ample reason to expect the technology to be in use in the not-too-distant future. Solar hybrids are on the way to car showrooms and commercial fleets, and electricity harnessed from the sun may be used to power vehicles at charging stations, avoiding a stressed grid.