The fact that the vast majority of the continent’s rooftop panels are installed by thousands of small firms means there is little chance of achieving economies of scale that can bring costs down.

Marie Donnelly, head of renewables at the European Commission, describes rooftop installation as “one of the key areas for cost reduction”.

“This is something we really have to look at — [the installers’] capacity, skills, knowledge and the efficiency of the installation of PV,” she told a recent solar conference.

And