The decision by the French and Italian governments to offer more attractive feed-in tariffs to companies that install solar technologies that are integrated into the roof of a building has led to booming demand for such systems, which is threatening to outstrip supply.

That is the view of Randy McEwan, chief executive of Solar Integrated, a US firm specialising in solar panels that are integrated into the fabric of the roof. He claims that sales in Europe are on course to more than double this year, primarily as a result of the attractive feed-in tariffs available in France and Italy.

Feed-in tariffs, which guarantee generators of renewable energy an above-market price for any power they sell back to the grid, have proved a popular mechanism for promoting adoption of onsite renewable energy across much of the continent, with ground- and roof-mounted solar panels the main beneficiary.

However, the French and German governments have sought to tilt the tariffs in favour of less visually intrusive solar panels that are largely indistinguishable from the roof of a building. In France, power fed back to the grid from building integrated solar technologies can be sold for 55 cents/Kwh, compared to 30 cents/Kwh for power from conventional panels. While in Italy, integrated solar technologies command a six cent/Kwh premium compared to mounted systems.

McEwan said the result has been a huge increase in demand for the company's thin film integrated solar technologies, which he claimed can be fitted to a commercial property's flat or gently sloping roof without leading to any reduction in the roof's integrity, and provide better energy yields in low lights than traditional crystalline solar panels.

The company saw sales more than double in 2007 to $81m (£40.5m) and is projecting that sales will almost double again this year to between $140 and $160m. "Europe is at the forefront of our expansion," said McEwan. "It accounted for 38 per cent of our sales last year, but we expect it to be up to 60 to 70 per cent of revenue this year. It is really down to the new markets that have been opened up by these feed-in tariffs."

McEwan insisted that the main inhibitor to further growth in the sector was meeting the soaring demand. "We have supply agreements in place that mean we can meet our long-term growth commitments," he said. "But when you look at the two largest providers of thin film solar panels at the moment they are sold out." However, he remained optimistic that supply would increase to meet demand across the industry, observing that "both the existing players and new firms are all looking to scale up their operations".