Should the product of the losses in the loss diagram (aside from transposition) give the performance ratio? And by product I mean (1 - loss)*(1 + gain)... etc. My understanding is that the "Global horizontal irradiation" is transposed to "Global incident in coll. plane" which is GlobInc. and the final energy is E_grid. The efficiency times the module surface area gives PnomPV and so the product of the losses gives PR according to the following equation: E_Grid = GlobInc x PnomPV x PR From loss diagram: E_grid = GHI x Transposition x Optical_losses x Module_area x Efficiency x Other_losses = GlobInc x Optical_losses x PnomPV x Other_losses = GlobInc x PnomPV x Total_losses