Help calculating electricity home usage

[TenTwenty]

Hi

The program I'm working on is to help me determine my monthly electricity usage taking into account the cost 4 tables in the excel file.
If I make a payment then usually it will span over 2 months. I just can not find how to get it right as what I have is not correct. The single payment should thus be splint between 2 months to be able to calculate the average usage a month. Then, to screw myself further, there are a few payments where there was more than one payment made on the same month.

The data is there, pivot and graphs but the results is not what I want. Created a new sheet to change values and formulas but keep running into a wall now.

Hope this Dropbox link to the Excel file will help. To explain here is impossible.

Regards to those who take a dab at this. It's much appreciated.

https://www.dropbox.com/s/to2h0otsal7mtvw/Eplain.xlsx?dl=0

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