NaN Pay back period

Hello,

I was trying to do an analysis for residential Solar PV. I am using SAM for the first time and i am still trying to understand the terms and ways of providing inputs.
I get a NaN value on the pay back period and my NPV is negative. What does it mean and am I making a mistake?

Also, the Electric load tab has something called Energy Usage with edit data option. What energy usage does this represent? And I have not noticed a way of entering the usage of the building where I intend to install solar panels. How does it calculate then? i do not understand what mistake I am making..

Someone help!

A value of "NaN" for the payback period means that the payback period is longer than the analysis period. ("NaN" stands for "not a number.") A negative net present value indicates that the project's total savings are less than its costs. Both are an indication that the project is not financially feasible given your assumptions.

The data on the Electric Load page describes the building or facility electric load. The energy usage input allows you to provide SAM with a table of data describing the building's electric load. You can find more details in the Help system.

Best regards,
Paul.