Photovoltaic array performance monitoring is disclosed herein. A photovoltaic array performance monitoring system may include a data acquisition unit coupled with reference and ambient photovoltaic panels. The reference photovoltaic panel is equipped with a soiling removal unit which periodically removes deposited soiling materials from an active photovoltaic collection area of the reference photovoltaic panel. The ambient photovoltaic panel accumulates light obscuring soiling materials at a rate approximately equal to those of a proximate photovoltaic array. The data acquisition unit periodically sends electrical energy measurements of the reference and ambient photovoltaic panels to a computing system. Over time, the electrical energy output differential between the reference and ambient photovoltaic panels exceeds a predetermined threshold. The computing system evaluates the electrical energy measurements and determines when it would be cost-effective to clean the photovoltaic array. The result is output in a human cognizable format and/or a machine readable format.