I am using the Single Owner financial model. Why does the IRR not change when I change system parameters like the solar field size?
The Single Owner and other PPA financial models provide an option on the Financial Parameters input page to either calculate the IRR as a result or provide the IRR as an input. If you choose the "Specify IRR target" option, then SAM will adjust the PPA price to mantain the IRR that you specify. With that option, as you change system design parameters, the IRR should remain the same, but the PPA price should change.
If you choose the "Specify PPA price" option, then the IRR should vary as you change design parameters and the PPA price should remain constant.
