High Quality Content by WIKIPEDIA articles! This page lists large-scale rooftop photovoltaic installation projects. Photovoltaic arrays in buildings are often either integrated into them, or mounted on to the their roofs. Arrays are most often retrofitted into existing buildings, usually mounted on top of the existing roof structure. In 2010, more than four-fifths of the 9,000 MW of solar PV operating in Germany was installed on rooftops.