I have a tendency to start pondering deep thoughts in the shower, and as such my water usage increases inappropriately. My wife (a staunch environmentalist) once quipped, "how much money would we save if you didn't take such a long shower?"
My short answer was "How much are we spending now?" Our water bill is about $32 every two months and our gas bill is $20/month. Guess what, it is less than that amount.
Both of those numbers were basically the base rate. Reducing our consumption would not reduce our bill.