Create a spreadsheet like above with the following formula in each of these cells:
In C5 enter this: =SUM(C2:C4)
In D5 enter this:=SUM(D2:D4)
In A7 enter the first Kwh Consumption noted on your old bill
In B7 enter the rate on the first amount usage from the old bill
In C7 enter this: =C5-A7
In D7 enter this: =C7*B7
In B8 enter the rate from the old bills on the rest of your consumption
In C8 enter this: =C5-C7
In D8 enter this: =C8*B8
In C9 enter this: =SUM(C7:C8) (it should be the same value as C5 when it displays)
In D9 enter this:=SUM(D7:D8)
In D11 enter this:=D9-D5
D11 will be the difference between TOU on your bill compared to what your bill would have been had TOU not applied. If positive TOU is saving you money, if negative, it's costing you.
You can copy all these cells and do a month on each worktab and follow what happens over the winter.
I would be most interested in gathering cases from anyone over the next months and come March post the results here.
If you are having problems setting this up I can email you a template to work with.