This paper describes a generalised approach to estimating mismatch loss for series connected cells, utilising the result that the deviation from maximum power as a function of deviation from maximum power-point-current is a relatively stable relationship for a wide range of cell performances. This Power-Current relationship can be used to verify the strong link between mismatch loss and the variance in the maximum power-point-current values for the cells being mixed together. The mismatch loss in a modern photovoltaic module is low - below 0.1% even when there is no cell sorting whatsoever. Cell-to-module variance effects need to be understood and controlled to ensure mismatch loss remains low in a finished module. Without the constraints of mismatch loss in module design, other motivations for cell sorting should be considered, such as for optimising the manufacturing system or meeting particular product requirements. (C) 2014 Elsevier B.V. All rights reserved.