Toyota is due to launch a third-generation Prius next year

Toyota is planning to add solar-powered air conditioning to high-end models of its Prius hybrid cars, a report says.

The new feature would be part of the third-generation Prius, which is due to be launched next year, according to the Nikkei business daily.

The solar panels will be made by Kyocera and will provide some of the two to five kilowatts used by the air conditioning system, it reported.

Toyota has a policy of not commenting on future product plans.

There has been some scepticism about whether the solar panels would generate a useful amount of electricity.

"Even if you laid solar panels out on the entire roof of a house, you only generate enough energy to run two hairdryers," said Kentaro Endo, a specialist on renewable energy from Japan's Ministry of Economy, Trade and Industry.

Sales of the Prius have been increasing as rising oil prices have made the better fuel consumption of its combined petrol engine and electric motor more attractive.

More than one million of the models have already been sold and Toyota aims to sell one million a year sometime after 2010.

Mazda briefly offered solar panels as an option on two of its models in the 1990s.

They were supposed to ventilate cars parked outside on hot days, but it was not a popular option and was soon discontinued.