A shower is flow × minutes. A typical modern head is about 2.0–2.1 gallons per minute. Eight minutes is about 17 gallons. Ten minutes is about 21. An older 2.5 gpm head or a rain head at 3+ gpm turns the same minutes into a different bill.
Hot water is also energy if the heater is electric or gas. This card is gallons. The water-heater power card is the electric recovery. Both can be true for the same shower.
Two people × daily showers stacks faster than one long weekly bath in many houses. Low-flow heads cut gallons without needing a shorter song in the bathroom.
Whatt starts many shower cards near 2.1 gpm and 8 minutes. Change the head and the time. What-ifs add 5 or 10 minutes.
At a typical 5.00 per 1,000 gallons, 21 gallons is about 0.11 of water volume. That does not include sewer minimums or the electricity to heat it. The point is the minutes, not a mystery fee.
Head vs heater
The shower card is gallons. Electric or gas recovery is how the water is heated — look at the tank, not the head. Two people daily stacks faster than one long weekly bath for many houses.
Related
Usage estimate only — not a utility bill, load calc, or advice.