Shower water usage calculator
Enter the flow of your showerhead, how long a shower lasts and how many showers your household takes. You get litres and gallons used, and the cost of the water and of heating it using your own prices.
Runs in your browser: nothing you enter is sent anywhere.
How to use it
- Choose metric or imperial units.
- Enter the showerhead flow, minutes per shower, the number of showers per day for the whole household and the number of days.
- Enter your water price and energy price. Set the temperature rise and the heater efficiency to estimate heating.
- Read the water used, the water cost and the heating cost.
How it is calculated
- Water per shower = flow × minutes. Total = per shower × showers per day × days.
- Water cost = total litres ÷ 1,000 × price per m³ (or gallons ÷ 1,000 × price per 1,000 gallons).
- Heating energy (kWh) = litres × temperature rise (°C) × 4.186 ÷ 3,600 ÷ efficiency.
- Heating cost = kWh × energy price.
Worked example
9 L/min for 8 minutes uses 72 L. Two showers a day for 30 days is 60 showers, so 4,320 L. At 2 per m³ the water costs 8.64. Heating by 25 °C needs 4,320 × 25 × 4.186 ÷ 3,600 = 125.58 kWh, which is 18.84 at 0.15 per kWh.
Tips
Reducing shower time by two minutes cuts both water and heating use by a quarter in this example. Check your own flow rate before trusting the defaults.
Frequently asked questions
How do I find my showerhead's flow rate?
It is often printed on the showerhead or in its manual. You can also measure it: run the shower into a bucket for 10 seconds, measure the water and multiply by six to get litres or gallons per minute.
How is the heating energy calculated?
Heating one litre of water by one degree Celsius takes 4.186 kJ, and a kWh is 3,600 kJ. The calculator multiplies litres by the temperature rise and divides by the heater's efficiency. A resistance electric heater is about 100 percent; a heat pump can be well above that.
What is the temperature rise?
The difference between the cold water entering your home and the water you shower in. Use your own estimate: 25 °C (45 °F) is only a default, and cold water is colder in winter.
Are gallons US or UK gallons?
US gallons (3.785 litres). The results show litres as well.
What currency are the prices in?
Whatever you type in; there is no conversion. Use the same currency for water and energy prices.