Field Performance of 1.7 GW of Photovoltaic Systems

This paper presents performance data from nearly 50 000 photovoltaic systems totaling 1.7 GW of capacity installed in the USA from 2009 to 2012. Most systems without reported issues, about 90%, produced greater than 90% of the electricity predicted before installation. The data were shown to be consistent with the assumption of historical degradation rates of about 0.5% per year; excessive degradation rates such as 2% or 3% per year were not observed. Large systems showed an insolation-adjusted yield that was about 4% higher than smaller systems. Only 2-4% of the data indicated issues significantly affecting system performance. Delays and interconnections dominate project-related issues particularly in the first year, but were reported in less than 0.5% of all systems. Hardware-related issues are dominated by inverter problems as reported for less than 0.4% and underperforming modules for less than 0.1%.