The Korean carmaker said up to 60% of the power for the car's battery could be supplied if the solar roof was used for six hours a day. The panels would provide enough power to propel the Sonata for 1,300km (800miles) a year Hyundai said it planned to offer the roof as an optional extra on other models in its range. It added that the mid-sized passenger car had an improved engine control system to ensure energy use was as efficient as possible.

Writing on the Digital Trends news site Stephen Edelstein said: "Hybrids like the Sonata have smaller battery packs than all-electric cars, so a solar roof can make a bigger difference in charging. Hyundai is working on a second-generation solar roof that would be semi-transparent to help light the car's cabin. Hyundai is not the first car manufacturer to use solar panels on a vehicle. The sun-powered charging systems are available as an option on the Toyota Prius, and the luxury Karma Revero is also available with one. In addition, Dutch start-up Lightyear is working on an electric car that uses solar panels on its bonnet and roof to help charge the vehicle's batteries.

The car is going to be on sale in 2021.