I don't know how much my current shower flows at... I just take quick showers - and that's that. My water bill is usually around $10 to $13 each month - which is the lowest that they can bill me for.
But - it triggered a memory of long ago - when I rented my first apartment. There was a 5 gallon water heater that plugged into a 120-volt outlet. It heated the water, but if I took too long in the shower - I was getting blasted with cold water. In the summer - that might feel nice - but in the winter... nope!
So, I had to learn how to turn on the water (no time to let it warm up) - get wet - and turn it off. Then - soap up - and turn on the water again to rinse off. If I took too long doing this - I would get an instant ice-bath. (I remember my girlfriend and I taking a quick shower together one time - and her squeeling when the cold water hit.)
I guess that was my 'training' for taking quick showers.
I didn't like the fact that the water heater was always 'on' and heating the water - even when I didn't need it - and so purchased an electric timer, which I plugged in and had the heater turn on about an hour before I got up in the morning. It would heat the water for about 2 hours or so - which was adequate for me. If I needed hot water for washing the dishes - I would bypass the timer and plug the heater directly into the wall.
Needless to say - my electric bill dropped quite a bit.
Regards,
Jim TX