Online map helps you see if solar panels work for you

FOR anyone interested in checking if their rooftop is viable for solar photovoltaic panels, a website offers a snapshot of the potential pluses and minuses along with rough but fairly accurate cash figures.

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Called In Sun We Trust, the website at lets you pinpoint your address on a map of France, give details of the roof and it then calculates an estimate of the costs, the pay-back time and how much you can potentially ‘make’ from PV panels.

With its position in southern Europe France has a natural advantage in using solar energy and the national energy agency Ademe says that if solar PV panels were installed on all of the country’s rooftops it could supply 364GW or enough for 80% of its energy needs.

Today it has just 6,737mW of solar power production and that is part of what pushed former investment banker David Calle­gari and engineer and solar re­searcher Nicolas Bodereau to set up the site.

They had been working on large-scale solar power projects but had been appalled at the slow pace of uptake of what they see as a natural bonus for France.

They used a Twitter account to pass on information on technical advances and noticed that more and householders were asking where to get proper advice on the suitability of their roofs – and, with a wave of con tricks having been revealed, how to avoid being defrauded.

They set up In Sun We Trust last year as a one-stop shop where householders could get an evaluation of their roof and, crucially, where they could be put in touch with screened and accredited installation engineers who could advise on their project and carry out all the work.

Their efforts were recognised when the site was showcased at last year’s COP21 environmental summit in Paris and named one of France’s top energy transition projects.

Despite its name, In Sun We Trust is 100% French and Mr Callegari said they worked with IGN, the Institut National de l’Information Géographique, to create a 3D map of France; working out if roofs would be affected by shadows (from buildings, trees, surrounding landscape), and the engineering college Mines ParisTech developed the mathematical algorithms to calculate the solar exposure and likely effectiveness of any PV installation.

In the Dordogne a south-facing site at Sal­ignac was estimated to cost €27,500 for 50m2 of panels, with all power sold on a 20-year contract to EDF at 24.64centimes per kilowatt hour bringing in €56,000. It would pay for itself in 10 years.

If householders are interested by the results of their own simulation they can get a pdf with details and can ask for an estimate and real quote from a recommended engineer in the area. Engineers can also estimate benefits if clients opt to use some of the power for their own needs and cut bills, called autoconsommation, but selling the energy could earn twice what they would pay.

Mr Callegari added “Solar panels are not for everyone: the costs and returns may not add up and what works in the sunny south may not be good for the cloudier north, but they could make a significant difference for householders from Pas-de-Calais across to Brittany and down to the Mediterranean coast – where there are simply not enough people taking advantage of solar power.”

Householders do not need planning permission for small-scale projects, but must make a déclaration préalable to the mairie.

Installation takes just a few days but the administration work, which is done by the engineer, could take a couple of months or longer to agree and sign with EDF.