The Hyundai Ioniq 5 was one of the first mainstream electric cars to offer a solar roof, showing that the tech was not just for concept cars. Rather than replacing conventional charging, the optional roof uses photovoltaic cells to trickle charge the high-voltage battery whenever the car is parked or driving in sunlight. Hyundai estimates that, in ideal conditions, it could add around 1000 miles of driving over the course of a year.

In reality, the benefits depend heavily on where you live and how often the car is left outside. UK drivers are unlikely to see the same gains as those in sunnier climes, but it all helps. The solar roof also reduces the amount of energy drawn from the battery to support the car's electrical systems, helping to eke out a little more range. Combined with the Ioniq 5's impressive efficiency and distinctive retro-inspired styling, it's one of the best examples of production solar technology available today.

The latest Mercedes-Benz CLA introduces one of the most sophisticated solar roof systems yet fitted to a production car. Inspired by the Vision EQXX concept, the roof incorporates around 170 ultra-thin solar cells that continuously generate electricity whenever exposed to sunlight.

Rather than attempting to charge the main drive battery directly, Mercedes uses the energy to support the car's 12V electrical system. That means features such as the infotainment system and lighting use less energy from the high-voltage battery. Mercedes estimates that, depending on climate and usage, the system can contribute a "useful amount" of free energy over the course of a year. However that much may be.

It's an approach that works within the current limitations of solar technology. Instead of making promises about dramatically increasing driving range, Mercedes uses the panels to reduce the car's everyday energy consumption.

Toyota has been experimenting with solar roofs for more than 15 years, and the latest Toyota Prius Plug-in Hybrid features one of the most advanced systems currently available. Unlike earlier versions that simply powered the ventilation system, the latest roof can generate electricity for both the 12V battery and – under the right conditions – feed energy into the traction battery. Unfortunately while it's available elsewhere, Toyota hasn't launched it in the UK yet.

Toyota says this can add several miles of electric range over the course of a sunny day, although the UK weather would mean most owners would see smaller gains. Which is probably why Toyota is reluctant to launch it here. 

The biggest benefit comes from reducing the amount of electricity that needs to come from the mains, lowering running costs over time. It also helps keep the auxiliary battery charged if the car is left parked for long periods. While it's no substitute for plugging in, the Prius demonstrates how solar technology is becoming a useful supplement rather than just an interesting novelty.

Toyota's first dedicated electric SUV, the Toyota bZ4X is available with an optional solar roof in some countries, although we're still waiting for it to come to the UK. The roof continuously generate energy from sunlight when conditions allow, helping to reduce the amount of power drawn from the grid.

Like every production solar roof currently on sale, the gains are modest rather than exceptional. The panels won't eliminate charging, but they can add some energy while the car sits parked outside at home or work. The system also helps support the vehicle's electrical systems, improving overall efficiency.

The bZ4X has a heat pump fitted as standard and aerodynamic detailing to maximise range. The solar roof gives owners another small but useful way to reduce energy consumption. Hopefully it comes to the UK sooner rather than later.

Although it has never officially been sold in the UK, the Hyundai Sonata Hybrid deserves a mention because it helped bring solar roofs into the mainstream. Introduced in 2019, its optional solar roof was designed to top up the hybrid battery while the car was parked or driving, with Hyundai claiming it could recover enough electricity to provide around 800 to 1,000 miles of additional driving over the course of a year. In favourable conditions of course.

The Sonata also shows that solar panels can be integrated neatly into a family car without making it look awful. Crucially perhaps, it's a good example of solar technology adding real-world range rather than simply being a gimmick. Much of what Hyundai learned from the Sonata has since been applied to newer electric models such as the Hyundai Ioniq 5, making it an important milestone in the development of solar tech in cars.

No list of solar-powered cars would be complete without the Lightyear 0. Built by Dutch start-up Lightyear, it was the world's first production car designed around solar charging rather than treating it as an optional extra. Five square metres of solar panels were integrated into the roof and bonnet, allowing the car to recover energy whenever it was exposed to sunlight.

In ideal conditions, Lightyear claimed owners could cover thousands of miles each year using solar energy alone, particularly in sunny climates. That made it unlike any other production EV. Unfortunately, its innovative engineering came at a huge cost, with prices exceeding €250,000, and production ended after only a handful of cars were built.

Although commercially unsuccessful, the Lightyear 0 proved that solar-powered motoring is technically possible. Many of the lessons learned from the project are likely to influence future production cars as solar technology becomes cheaper, lighter and more efficient.