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P75 Evaluation for 25 years simulation


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PV Syst version 7.3 generates report based on the P50 evaluation specifically for the 25-year simulation. Need help if it is possible to do a simulation for P75 evaluation also for 25 years for the yearly yield and PR.

Based on what I have read P50 is default is there a way to change it to P75? another one question how to manually compute for P75 what is the multiplier?


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Hi, I don't think that the concepts of P50 and P75 always apply well to simulations over multiple years.

Basically you get a P50 result when you simulate with an "average year" and "average parameters". When you run 25 years of simulations there are two cases:

- You are using the same weather input file (an "average" one) for all of the simulations, and what changes is just the aging. In this case, it could make sense to call the results for each year a P50 estimate. However the P75, P90 etc depend on the uncertainty of the parameters (which you can define once in Energy management > P50/P90 estimation). For 25 years you would probably need to increase the uncertainty of the aging parameters as the years go by. This is not yet implemented.

- You are using a time series to run 25 years. In this case you are not using "average weather files". So it is not possible to get a P50 value from that. You can use a 25 year time series to get a TMY with PVsyst. Using that file as "average weather" file will bring you back to the previous point.

The multiplier to get the P75 value depends on the width of the distribution. Given a standard deviation sigma, the multiplier is (1-0.674*sigma).

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  • 2 weeks later...

The simulation is considered as P50 when it is based on average  meteo data (synthetic generation from averaged monthly data),  or typical meteological year data (TMY).

Creating a simulation corresponding to P90 doesn’t make much sense.  What would be the use of such a simulation results, when the P90 statistical approach only concerns the yearly result?

You cannot say that each month has P90 monthly results, as the variability of monthly results is obviously much higher than the annual variability. Therefore you cannot compare the monthly values with the measured ones on a real system  (this is also true for the P50).

Performing such a simulation  would need to avail of a Meteo data file representing P90 weather data.  Some Meteo data providers may elaborate such files, but we have some doubts about the validity of tis methodology.

Please carefully read the Help  “Project design > P50 - P90 evaluations”  for understanding the deep meaning of such statistical evaluation, based on the annual variability of the meteo conditions.

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