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Low-Flow Showerhead Savings Calculator

Enter your old and new flow rates to see your yearly water and cost savings.

How it is calculated

The saving per person-minute is the drop in flow rate. gallons saved per day = (old gpm − new gpm) × minutes per person per day × people, and the yearly figure is that times 365. cost saved = gallons saved per year × water cost per gallon. Flow rates are in gallons per minute (gpm), the water cost is the price you pay for one gallon, and minutes are the shower time of one person per day. The new flow rate must be lower than the old one; otherwise there is no result. The tool counts only the water bill. Savings on heating the water, sewer charges that are billed separately, and changes in how long people shower are not included.

Worked example

Three people each shower 8 minutes a day. The old showerhead runs at 2.5 gpm and the new one at 1.5 gpm, with water at 0.005 per gallon. Daily saving: (2.5 − 1.5) × 8 × 3 = 24 gallons, shown as 24 gal. Yearly: 24 × 365 = 8,760 gallons, shown as 8,760 gal. Cost saved: 8,760 × 0.005 = 43.80, so about $43.80 a year on the water bill alone.

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Common mistakes

  • Entering the water price per 1,000 gallons or per cubic metre. The tool multiplies by gallons, so the price must be per single gallon, a small number such as 0.005.
  • Entering total household shower minutes in the per-person field. The tool multiplies by the number of people, so enter the minutes for one person only.
  • Using the rated flow of the box rather than the actual flow. The old showerhead may be restricted by low supply pressure, so measure with a bucket and a timer if you can.
  • Entering flow in litres per minute. The labels are gallons per minute, so convert litres first (about 3.785 litres to a gallon).
  • Assuming the same showering time with the new head. If people stay in longer because the flow feels weaker, the real saving is lower.

About this calculator

Water savings from switching showerheads come down to the difference in flow rate: an older standard showerhead often runs at 2.5 gallons per minute (the US federal maximum since 1992) or higher on pre-1992 fixtures, while an EPA WaterSense-certified low-flow showerhead uses 2.0 gallons per minute or less without sacrificing pressure, thanks to aerating or pulsing nozzle designs. Multiplying the flow-rate difference by the minutes of shower time per day, the number of people and 365 days gives total gallons saved annually.

Because a large share of that water was also heated, real savings extend beyond the water bill to the energy cost of heating less water — which is why utilities and water conservation programs often promote low-flow fixtures as one of the highest-return, lowest-effort upgrades a household can make. Heating energy saved is not counted, so actual savings will run somewhat higher than the estimate.

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Comments (1)

  • Editorial team

    This counts water and its price only. The hot water you no longer heat is often the larger saving, and it is not included. Also note that the water cost field is per gallon, so a rate quoted at 6 per 1,000 gallons goes in as 0.006. Time how long a bucket takes to fill to measure your own flow. What flow rate did you find?

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