Performance of distributed PV in the UK: a statistical analysis of over 7000 systems

In June 2015, the UK fleet of solar photovoltaic (PV) systems reached 7.8 GWp of capacity, but there are wide gaps in our understanding of the performance of these systems, which has lead to the conservative limit of 10 GWp being imposed on UK PV capacity by the Department of Energy and Climate Change. Here we present the results of a statistical analysis of real world UK PV systems which donate data to the Microgen Database, of which there are over 7000. The mean yearly-integrated Performance Ratio (PR) of domestic scale UK PV is 83% with a standard deviation of 7%. By considering yearly-integrated PR, we have shown that 4.1 % of systems suffered long-term underperformance relative to their nominal efficiencies during 2013. The mean degradation rate for crystalline Siliconbased PV systems in the UK is -0.8 ± 0.1% per year. The state-of-the-art of UK PV, in terms of technology, manufacturing, and installation-standards, is found to have increased by 1% per year between 2002 and 2013