Values for "DC to AC ratio" and "Losses"

I need help with putting correct input values in SAM.

Question 1:
If my system has DC to AC derate factor of 85%, then what should I use for DC to AC ratio in SAM? Default value in SAM is 1.2 and it confuses me whether I have to put 1.15 or 0.85 or some other value.

Question 2:
If I knew my solar panel efficiency is 15%, how can I input that into the SAM model? Would I set total system losses to 85%? Or is there some other way to input this?

Hello,

The DC-to-AC ratio for a photovoltaic system is the ratio of the photovoltaic array's nameplate DC capacity in kW to the inverter's nameplate AC capacity in kW. Here is an example:

Nameplate capacity of one module (maximum power rating at STC): 0.335 DC kW
Number of modules in array: 14
Nameplate capacity of array: 0.335 DC kW * 14 modules = 4.69 DC kW
Nameplate capacity of one inverter (maximum AC power) = 3.800 AC kW
Number of inverters in system: 1
Total inverter nameplate capacity: 3.800 AC kW * 1 inverter = 3.800 AC kW
DC-to-AC ratio : 4.69 DC kW / 3.800 AC kW = 1.23

The photovoltaic module rated efficiency is an input only for the Simple Efficiency Module model. For the CEC Performance Model with Module Database module model, you provide parameters to describe the properties of the module, and SAM calculates the resulting efficiency. If you want to model a system that uses modules with 15% nominal efficiency, you can either use the Simple Efficiency model, or you can use the CEC model and choose a module with about 15% efficiency like one of the Canadian Solar CS6K modules.

Best regards,
Paul.