Dear Rana,
There are a few things going on here:
First, I think there is a bug in how SAM calculates the Energy Yield (kWh/kW) with subhourly simulations. For one-minute data, if you multiply the number SAM reports by 60 minutes, you should get the correct value. You can see the value with more significant digits on the Data Tables tab of the Results page by displaying the "First year kWh/kW)" variable under Single Values. We are investigating that and will fix it the next time we update SAM.
Is your weather file for a location near Knoxville, TN? If so, the longitude should be negative 84.3 rather than positive 84.3.
In order for SAM's bill calculations to be accurate, when you use subhourly weather data, you should also use subhourly load data. In your case, you are using one-minute weather data with 60-minute load data.
I think the net present value and payback period values are reasonable given the project costs you have defined. You may want to experiment using hourly data first (perhaps the TMY2 file for Knoxville that comes with SAM for the weather file) to find a combination of financial assumptions that produce the results for payback period and net present value that you expect, and then switch to the subhourly data once you have results that make sense.
Thanks,
Paul.
