A friend asked me to help him approximate monthly electricity spend/usage using data from prepaid electricity purchases over irregular dates a period of time. The data contains: Date Amount spent (including tax) Amount of electricity purchased Price Before Tax The purchases were made on irregular intervals based on need. My approach using MS Excel is on this link, involves allocating the purchases to months based on the days in between the purchases to extract monthly and quarterly usage. I believe I would have to ignore the first and last purchases because: The first is not from the beginning of the month There is still some unused electricity from the last purchase. I would appreciate any comments on a better approach. Additionally, I noticed there was no purchase in Oct 2022 and this shows as no purchase (or electricity use) which is obviously wrong. Thanks
