American, Canadian and European university students battle for architectural and engineering supremacy in Washington this month in a contest of homes whose lights, refrigerators and televisions must be powered by solar energy.

Twenty teams will show off their futuristic creations at the third edition of "Solar Decathlon 2007" between October 12-20 in the US capital's vast Mall esplanade, and 125,000 people are expected to visit the homes.

Construction and engineering experts will judge the homes using 10 criteria including architecture, engineering, market viability, interior comfort and whether the sun actually powers appliances and produces hot water.

The solar power going through the homes must also be able to charge an electric car.

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