I need my half hourly electricity consumption data totalling for two different time periods to evaluate total costs for peak and off peak usage.

I am looking for assistance to analyze my electricity consumption data. Specifically, I need the data from 2 different time periods tallied up and evaluated in terms of total cost for peak and off peak usage. The data I have is in spreadsheet format, and I have a clear method of evaluation. Your role will be to take this data, calculate the total kWh's used between 05:30am-23:30pm & 23:30pm-05:30am, create these two separate total kWh's so that when I import a years worth of data, it will automatically give me the corresponding values in total kWh's used, so I can create a cost comparison between peak/off peak usage.