Hi Benjamin,
SAM's electricity bill calculator assumes that the first time step in the simulation is in the first hour of Monday, January 1. When you provide time series electricity rate data as input, SAM automatically considers it to be hourly data if has 8,760 rows, 15-minute data if it has 35,040 rows, etc. You do not need to specify time stamps or time resolution in the .csv file.
SAM only accepts electricity rate data for Year 1. If you are providing hourly time series data, it should contain 8760 values.
You can use the electricity bill escalation rate to adjust the rates in future years.
Best regards,
Paul.