Monitoring bathroom water usage is a smart way to cut down on your water bill while conserving a precious natural resource. You're likely to save on more than just the water bill--when less hot water is used, your water heater takes a break, saving you money on your electric bill, too. Federal regulations continue to tighten on showerhead manufacturing, producing lower flow rates. However, these regulations only affect new showerheads; if you're stuck with an old one, an upgrade can save as much as 8 gallons per minute.
Bath Water Usage
Bath water usage is relatively standard per bath, unlike shower water usage. Most baths use an estimated 30 to 50 gallons. If you're the type to drain some of the cooled water and add more hot water during the course of the bath, add another 5 to 10 gallons to that total.
Shower Water Usage
Any measure of how much water you use while taking a shower depends on how long you're in it as well as the type of shower head you have. The California Energy Commission estimates that showerheads made after 1992 use around five gallons per minute. Without water-saving features, older shower heads can put out 7 to 10 gallons per minute. However, if you have or install a brand-new showerhead, federal regulations limit the flow to 2.5 gallons per minute.
Sample Calculations
If you have a post-1992 showerhead and take a 10-minute shower, you're using 50 gallons of water. If you have a pre-1992 showerhead, that figure swells to between 70 and 100 gallons. If you have a brand-new low-flow showerhead, however, that figure drops to 25 gallons. Compare these numbers with a 40-gallon bath and you'll see the results are mixed.
Conclusions
If you limit the amount of time you're in the shower to five minutes, it will almost always use less water than a bath. If you're prone to 20-minute showers, even with a water-saving shower head, you're better off taking a bath to luxuriate. If you try and hit the middle ground with a moderately timed shower of around seven minutes, you're likely to break even, using roughly the same amount of water as a bath.
Low-Flow Recommendations
The Environmental Protection Agency estimates that each U.S. home uses 30 gallons per day to shower, for a grand total of 1.2 trillion gallons of shower water per year. To help cut that number, the EPA has created the WaterSense program. The program designates products designed specifically to help people cut their water usage. To be a certified WaterSense showerhead, the unit must meet a strict 2 gallons-per-minute flow rate, as tested by an independent lab. Showerheads meeting the criteria bear a WaterSense label on their packaging. With that flow rate, even a 20-minute shower could likely break even with a bath's water usage.
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