Showering is one of the leading ways we use water in the home, accounting for nearly 17 percent of residential indoor water use—for the average family, that adds up to nearly 40 gallons per day. That's nearly 1.2 trillion gallons of water used in the United States annually just for showering, or enough to supply the water needs of New York and New Jersey for a year!
Did you know that standard showerheads use 2.5 gallons of water per minute (gpm)? Water–saving showerheads that earn the WaterSense label must demonstrate that they use no more than 2.0 gpm. EPA worked with a variety of stakeholders—including consumers who tested various showerheads—to develop criteria for water coverage and spray intensity. All products bearing the WaterSense label—including water–efficient showerheads—must be independently certified to ensure they meet EPA water efficiency and performance criteria.
The average family could save 2,900 gallons per year by installing WaterSense labeled showerheads. Since these water savings will reduce demands on water heaters, they will also save energy. In fact, the average family could save more than 370 kilowatt hours of electricity annually, enough to power a house for 13 days.
On a national scale, if every home in the United States installed WaterSense labeled showerheads, we could save more than $2.2 billion in water utility bills and more than 260 billion gallons of water annually. In addition, we could avoid about $2.6 billion in energy costs for heating water.
Source: http://www3.epa.gov/watersense