PVWatts v6 API not matching Pvwattsv5

Hi,
I am running Pvwattsv5 in PySAM and loading the solar data from the nsrdb PSM-TMY endpoint. Nevertheless, I am not able to match the production value returned from PVWatts v6 API. The weather file seems to have the same identifier for both and I am sending the same input data (including dc-ac-ratio of 1.2). What exactly is the weather data used by the v6 API and will it load different values than those returned by the `/nsrdb/v2/solar/psm3-tmy-download` endpoint? 

Thank you,
Seb

Hi Seb,

The PVWatts V6 API should give results consistent with the PVWatts Online Calculator. It uses a different set of weather files than the endpoint you mention below, which is current data available from the NREL National Solar Radiation Database (NSRDB). If you use pvwattsv5 with data from the NSRDB you will get different results than from the PVWatts V6 API.

The PVWatts V6 API does include time stamp and weather data in the hourly outputs along with the latitude, longitude, and elevation data required for sun position calculations, so you could use that to either construct a weather file in the SAM CSV format to use with the 'solar_resource_file' input to pvwattsv5, or to pass data as a table to the 'solar_resource_data' input. Note that the time zone is also required, so you would have to provide that as well.

Best regards,
Paul.

Hi Paul,

Thanks for the response! Are the weather files that PVWatts V6 API uses available somewhere (i.e. an endpoint just like psm3-tmy)? My goal is to have an offline PySAM service that can replicate the results of the v6 API (assuming I can access the weather files somewhere else). Is that possible?

Thanks again,
Seb

Hi Seb,

Sorry, there is not an endpoint that returns the weather files that PVWatts V6 API uses.

Best regards,
Paul.