Hi Blessing,
SAM's PV and battery storage models run a simulation over the project life. If you use an hourly weather file for an analysis period of 25 years, you end up with 1 time step/hour * 8760 hours/year * 25 years = 219000 time steps.
The weather file only contains one year of data, so SAM uses the same weather file for the entire analysis period. This is appropriate when you file contains
typical meteorological year (TMY)
data that uses one year's worth of data to represent the solar resource over a historical period.
SAM displays weather and other time series data that does not vary from year to year under the "Hourly Data" category in tables and graphs on the Results page -- for hourly simulations, these data arrays have 8760 values. It displays data that is calculated over the analysis period under the "Lifetime Hourly Data" category -- for hourly simulations over 25 years, these would have 219000 values.
Best regards,
Paul.