mismatching night consumption at same AC capacity

[mohaned]

Hi PVsyst support team,

While running different scenarios (different DC/AC ratio) for the same inverter, I noticed that the hourly night consumption for each run is a different, ranging from 2.335 for one simulation down to 1.9945 for another simulation. 

My understanding is that the night losses are mainly related to the transformer iron losses. but my inverter quantity and all the losses I maintained constant. 

[André Mermoud]

Probably you have defined your transformer by a generic relative loss, i.e. proportional to the transformer nominal power.  And this nominal power - evaluated by PVsyst on the basis of the PNomPV at STC, or the PNomac  (this is your choice in the Project's settings) - has been changed in your different runs. 

This should not arise if you define an explicit transformer from the datasheets, the nominal power of the transformer will always remain the manufacturer's value. In this case the "generic" relative values will be updated as a function of this  real Transformer nominal power.