LCOE changes with different PPA values, even without debt, taxes, etc

Hi NREL forum (aka probably Paul!),
For my thesis project, I need to calculate the LCOE for a PV system, and be able to compare these costs across different sized systems.

SAM seems like the right tool for this. However, I am getting different LCOE values if I set different PPA values, regardless of whether there is debt financing or not. I understand that debt costs factor into the LCOE calculation in SAM, and have read the help documentation in SAM as well as anything on the forum having to do with LCOE. To isolate this factor, I set the debt percentage to zero, and I’ve even tried removing all taxes and depreciation income and the LCOE will still change when I change the PPA price. 
How can I calculate an LCOE that is not dependent on the PPA price and is instead purely dependent on the non-financing costs of the system?
If it helps, the project is a single owner photovoltaic system, and I am running it on a mac.

Thank you,
- Colin Schimmelfing

Hi Colin,

I've set up the attached file with no debt and no income taxes so that the LCOE does not change with PPA price with the following results:



If you continue to see different results, please send me a copy of your .sam file so I can investigate.

Best regards,
Paul.

Ah - looks like PVWatts - Single Owner does what I expect, but Photovoltaic - Single Owner does not (see attached). Weird! I should have been more specific as to which type of model I was using in my question.
I'll move my stuff over to PVWatts - Single Owner.
Thank you,
- Colin

Ah - I see - I was using the 'DSCR' value instead of fixed payments. Setting the debt to use fixed payments gave me consistent LCOE values.

Hi Colin,

Yes, using the "DSCR" option for debt sizing means that the size of debt depends on revenue available for debt service. Changing the PPA price changes revenue,  which in turn changes the size of debt. The resulting change in the initial investment and debt payments causes changes in the LCOE.

Best regards,
Paul.

Hmm - ok, I think I spoke too quickly last night.
I think it is a difference between PVWatts and PV-SingleOwner, and unfortunately I do need the functionality of PV-SingleOwner.
If you look in the attached file, even with no DSCR there is still a change in the real LCOE with a change in the PPA. 
For instance, I chose a PPA of $0.10 / kWh which gave a real LCOE of 4.58 cents / kWh, but when I chose a PPA of $0.05 / kWh I get a real LCOE of 3.44 cents.
Can you check this out to see if I'm missing something basic?
Thank you,
- Colin