Third Party - Host/Developer - Allocation of electricity export

Hi Paul, NREL Team,
My colleagues and I have been using SAM in our engineering team for quite a while now and have become big fans of the software.
We're now trying to replicate our financial model in SAM to make it our end-to-end platform for solar production estimates and running the financials.
One thing we are still struggling with, is having the revenue of exported solar power allocated to the developer. That's how our company's model works but it seems that SAM makes the assumption that the host buys 100% of the solar power from the developer and therefore also owns the export. Is there a way we can reflect having the host only buying the self-consumption part of the solar production and the revenue from exported (excess) power being owned by the developer?

Many thanks,
Alex Fischer
solarZero New Zealand

Hi Alex,

SAM's Third Party / Host Developer model assumes that the host sells all of the power generated by the system to the developer at an agreed-upon power prices (PPA price). The developer builds, owns, and operates the system and benefits from all incentives and tax credits. The host uses the power to reduce their electricity bill. The project is only economically viable to the host if the electricity bill savings are greater than the cost of purchasing electricity. The "host indifference point" is the PPA price at which the cost of purchasing power is the same as the value of the electricity bill savings.

I can't think of a way to force SAM to only consider purchases for self consumption. You could use the time series "Electricity from grid" output data to calculate that cost.

If you have a financial model implemented in Excel, you could write an LK script to calculate the cost in SAM and automatically export the data to Excel. LK is SAM's scripting language , which you can use to set the value of inputs, run simulations, export data, and for Windows versions of SAM, interact with an Excel workbook.

Best regards,
Paul.

Hi, So is there a way to model an on-site PPA in the traditional sense, where the host is purchasing only self-consumed energy from the developer? Or, do I need to model that separately using the outputs?

Hi Allison,

Are you looking at the host or developer perspective? Can you tell me more about the questions you are trying to answer?

Best regards,
Paul.

Hi Paul,

I am trying to look from the Host perspective. I want to understand the PPA price that they could expect. The problem as I understand it is that the PPA price calculated in this model is assumed that all the energy produced onsite is being sold to the developer, when in reality some would be self-consumed, some would go back to the grid, and some energy would be purchased from the grid. 

I'm still a bit confused as to whether I can accomplish these goals with the Host/Developer model, and if so, which metrics to use.