Hello. I'm running some simulations now and I noticed something I would like you to help me understand, reading the definition of PR from PVsyst I build a calculations sheet in excel and so far all the PR from PVsyst simulation result where succesfully coincident with the ones in the calculations sheet. (refer to Image 1 to Image 3). Values used to calculate PR where: PR = (E_Grid/E_AvailableMax) *100 E_AvailableMax = Efficiency Noct * A_collector * GlobInc All those values got from Simulatios Results. Image 1. http://imageshack.com/a/img661/8889/1ONbUN.jpg Image 2. http://imageshack.com/a/img537/7571/nrrzVS.jpg Image 3. http://imageshack.com/a/img631/3183/U5IhU0.jpg As you can see, all the PR values from Calculations match PR values from simulation results. My concern came out when I separate the system to ran the simulations for each orientation then I got what you can see in Image 3 (oriented 0°, south) and 4 (oriented 180°, north). Image 3. South http://imageshack.com/a/img913/8961/hR62nB.jpg Image 4. North http://imageshack.com/a/img910/3527/ufHdFM.jpg I was expeting for a result of PR from Image 3 to be greater than PR from Image 4, wich is not true because PVsyst calculated PR Image 3 = 69.2% < PR Image 4 = 70.2% Then, I ran the calculations sheet to get the values as I did in the global system simulations and got different PR for each subsystem and got the values I was expecting. http://imageshack.com/a/img673/664/y3Hh5h.jpg http://imageshack.com/a/img911/5743/bHWznR.jpg I realized that PVsyst calculates PR from the Yf / Yr relationship, I checked this in the Monthly tables results from simulation and the PR from those values matches the result from the simulations results, so I'm guessing the problem comes out from the Yf and Yr calculations wich a I have not checked how they were calculated. Please help me clarify that.