Payback NaN and LCOE

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Payback NaN and LCOE

Hi SAM Community

I'm trying to reproduce in SAM a Pre-Feasibility Study of a Small-Scale Concentrating Solar Power Plant in Sacramento.
I'm using CSP empirical as study demands.

The result that I consider the most important is the "payback" that according to the article is 28 years, but in my simulation it gives as a result NaN. I have entered all the data that the article demands but I think there are missing information that must be entered into the model.

I hope you could help me fixing this. I attach the model and the article.
My best regards.

Paul Gilman


A payback period of NaN ("Not a Number") often means that the payback period is longer than the analysis period. That combined with the negative net present value is an indication that the project costs outweigh its benefits. In this case, the cost of installing and operating the project is less than the electricity bill savings. This is being modeled using the Commercial financial model, which means that electricity generated by the system is used to reduce a building owner's electricity bill as defined by the load data on the Electric Load input page and the electricity rate structure defined on the Electricity Rates page.

According to the information in the article, the results published there were generated using SAM 2014.1.14 (the authors say 2014.4.1, but I think that may be a typo). If your goal is to exactly replicate those results, then you should use that version of SAM. You can download legacy versions of SAM from You must log on to the website to see the list of legacy versions.

The current version of SAM has new electricity bill calculations that I think are contributing to the difference in results you are seeing. It also looks like the solar field area in your file is different from the area shown in the article.

Best regards,

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