French Ecology Minister Ségolène Royal (above) officially opened the kilometer-long road on Wednesday. It took five years to develop and cost $5.2 million to produce and install the 30,000 square feet of solar panels. They're coated with a clear silicon resin that enables them to withstand the impact of passing traffic.

Being the first of its kind, the panels are still prohibitively expensive to produce en masse (they're also less efficient than conventional panels because they're laid flat rather than angled). But should Colas, the road's manufacturer, figure out how to get costs down and efficiency up, France may install them along another 1,000 kilometers of its roads.