# PRtemp calculation according to final report and hourly csv file

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Hello,

Recently I've been checking the results on PRtemp that PVSyst throws, based on the calculation they give in https://www.pvsyst.com/help/performance_ratio.htm which is indeed the one given by NREL and IEC 61724-1.

Below the results for a yearly TArrayAver= 40,79ºC. You can see the reults given by PVSyst and, in red, the ones manually calculated using the formulas mentioned above:

 Date Month TArray GlobInc E_Grid PR PR PR PR temp °C kWh/m²/mth MWh/mth ratio temp ratio 01/01/1990 1 18,829 98,151 4592,1 0,900 0,850 0,900 0,857 01/02/1990 2 22,082 124,36 5801,4 0,897 0,859 0,897 0,864 01/03/1990 3 26,722 176,88 8113,6 0,882 0,860 0,882 0,862 01/04/1990 4 30,465 216,64 9692,9 0,860 0,848 0,860 0,851 01/05/1990 5 37,29 270,47 11559 0,822 0,830 0,822 0,831 01/06/1990 6 42,159 292,54 12333 0,811 0,832 0,811 0,834 01/07/1990 7 47,381 321,19 13209 0,791 0,825 0,791 0,828 01/08/1990 8 47,486 288,4 12333 0,822 0,854 0,822 0,861 01/09/1990 9 40,079 212,27 9308,6 0,843 0,858 0,843 0,861 01/10/1990 10 32,068 154,07 6954,4 0,868 0,858 0,868 0,863 01/11/1990 11 23,085 103,25 4766,7 0,888 0,852 0,888 0,857 01/12/1990 12 18,789 88,653 4127,8 0,895 0,847 0,895 0,853 Yearly total 33,785 2346,9 102791 0,842 0,845 0,842 0,842

Does any one know how PVSyst calculates the PRtemp values? Seems like they are not using the formulas described in their manual.

Thank you!

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Yes PVsyst applies the definition of the PR (corrected) as it is defined in the help.

Now I don't know how you have done your calculation. This requires to be executed hour by hour (see the item "sum over hours").

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Thank you André,

Been checking my calculations and i am much convinced that they are correct. Yet, still don´t know why I obtain a different value for the PRtemp, must be then something odd with some value considered.

Had done it using the hourly csv exported from the advanced simulation option.

Thank you anyways