Derate factor

The derate factor by default is 0.77

The website seems unclear if the number is for no tracking, single axis, or 2 axis.
Could you suggest the appropriate multipliers

thanks

Hello,

I assume you are asking about the default value of the DC to AC derate factor for SAM's PVWatts model.

PVWatts calculates the incident radiation for each hour of the year based on the array's orientation and the sun's position in each hour. The derate factor is independent of the tracking option.

Best regards,
Paul.

I want to oversize the solar PV array comparatively to Inverter power, how to configure the derate factor greater than 1?

The PVWatts model assumes that the inverter AC capacity is equal to the array DC capacity, so it is inherently oversized by the inverter's conversion efficiency.

The Flat Plate PV model may be a better option for this kind of analysis. That model has a DC-to-AC ratio input (on the Array page).

Best regards,
Paul.