A method of manufacturing photovoltaic products in a manufacturing production line of a series of production steps (38, 42, 46, 50, 54, 58, 62, 66, 68), comprising, at each of a predetermined plurality of intermediate production steps of the production line: (a) assessing each photovoltaic product for suitability based on predetermined criteria for a preferred product, to obtain real time assessment results for the product at each production step; (b) storing the assessment results for that product by production step, in a memory; (c) assigning a grade to each photovoltaic product, based on either: (i) the assessment results for that product at that step; (ii) a comparison of the assessment results for that product at that step to statistical analysis of assessment results of previously processed photovoltaic products at that step; or (iii) a comparison of cumulative historical assessment results for the product at past production steps to a statistical analysis of historical cumulative assessment results of previously processed photovoltaic products over the same production steps; at each such production step, the grade identifying whether the product is within or outside of predetermined tolerances, representing deviations from the predetermined criteria, for photovoltaic products at such step; (d) storing the grade for that product at such production step, in a memory; and (e) using the grade to determine when and how the product is processed through downstream production steps. (a) assessing each photovoltaic product for suitability based on predetermined criteria for a preferred product, to obtain real time assessment results for the product at each production step; (b) storing the assessment results for that product by production step, in a memory; (c) assigning a grade to each photovoltaic product, based on either: (i) the assessment results for that product at that step; (ii) a comparison of the assessment results for that product at that step to statistical analysis of assessment results of previously processed photovoltaic products at that step; or (iii) a comparison of cumulative historical assessment results for the product at past production steps to a statistical analysis of historical cumulative assessment results of previously processed photovoltaic products over the same production steps; at each such production step, the grade identifying whether the product is within or outside of predetermined tolerances, representing deviations from the predetermined criteria, for photovoltaic products at such step; (i) the assessment results for that product at that step; (ii) a comparison of the assessment results for that product at that step to statistical analysis of assessment results of previously processed photovoltaic products at that step; or (iii) a comparison of cumulative historical assessment results for the product at past production steps to a statistical analysis of historical cumulative assessment results of previously processed photovoltaic products over the same production steps; (d) storing the grade for that product at such production step, in a memory; and (e) using the grade to determine when and how the product is processed through downstream production steps.