I also think it would be nice to add water usage to "the charts"
My water bill is split into water usage and sewer fees that are based on water used.
I have a GREAT natural water well that I am not using at this. I believe I can start using it to supply the house and just have a "sewer" bill.
It would be interesting to see if my Electricity bill rose from use of the electric well pump more than my water bill dropped.
All that said to suggest that if you implement water usage....do consider having the ability to split the sewer and water part.