A 1km (0.6-mile) route in the small village of Tourouvre-au-Perche covered with 2,800 sq m of electricity-generating panels, was inaugurated on Thursday by the ecology minister, Ségolène Royal.

It cost €5m (£4.2m) to construct and will be used by about 2,000 motorists a day during a two-year test period to establish if it can generate enough energy to power street lighting in the village of 3,400 residents.

In 2014, a solar-powered cycle path opened in Krommenie in the Netherlands and, despite teething problems, has generated 3,000kWh of energy – enough to power an average family home for a year. The cost of building the cycle path, however, could have paid for 520,000kWh.

Before the solar-powered road – called Wattway – was opened on the RD5 road, the panels were tested at four car parks across France. The constructor was Colas, part of giant telecoms group Bouygues, and financed by the state.

Normandy is not known for its surfeit of sunshine: Caen, the region’s political capital, enjoys just 44 days of strong sunshine a year compared with 170 in Marseilles.

Royal has said she would like to see solar panels installed on one in every 1,000km of French highway – France has a total of 1m km of roads – but panels laid on flat surfaces have been found to be less efficient than those installed on sloping areas such as roofs.

Critics say it is not a cost-effective use of public money. Marc Jedliczka, vice-president of Network for Energetic Transition (CLER) told Le Monde: “It’s without doubt a technical advance, but in order to develop renewables there are other priorities than a gadget of which we are more certain that it’s very expensive than the fact it works.”

Jean-Louis Bal, president of renewable energy union SER, said: “We have to look at the cost, the production [of electricity] and its lifespan. For now I don’t have the answers.”

Colas said the panels have been covered with a resin containing fine sheets of silicon, making them tough enough to withstand all traffic, including HGVs. The company says it hopes to reduce the costs of producing the solar panels and has about 100 other projects for solar-panelled roads – half in France and half abroad.

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