Dear James,
The adjust:factor input is for the "curtailment and availability" factors that you can see in the SAM user interface on the PVWatts System Design input page. Only the "Constant adjustment factor" adjust:factor is required, and you can set its value to 1 to model a system with no losses. This is true for versions of the SDK that you download before January 30, 2015.
We are preparing to release an update to SAM and the SDK in which we've changed those from factors to losses to be consistent with the rest of the mode. In that version, you would want to set the adjust:factor value to zero instead of one.
Please use SDKtool with your version of SSC to make sure you know whether your version is modeling the input as a set of loss factors with values between 0 and 1 or as a set of losses with values between 0 and 100%.
The purpose of this input is to model operational and other losses such as system curtailment, equipment downtime for maintenance, etc.
Best regards,
Paul.
