Heating water is one of the biggest energy uses in a home. A low-flow head or one minute less makes a measurable difference.
How to use the Shower Water and Energy Calculator
- Shower length
- Flow rate
- Showers per week
- Water heated by
- Energy price per kWh
Results update as you type, and every field accepts the units shown in its menu.
How it works
Water volume comes from time and flow; the energy to heat it comes from its specific heat and the temperature rise.
Inputs explained
| Field | What to enter |
|---|---|
| Shower length | In minutes |
| Flow rate | Units: L/min, US gal/min |
| Showers per week | A number |
| Water heated by | In °C |
| Energy price per kWh | Amount in your currency |
What each result means
- Water per shower = [Shower length]×[Flow rate]
- Energy per shower = [Water per shower]×4.186×[Water heated by]÷3600
- Water per year = [Water per shower]×[Showers per week]×52
- Heating cost per year = [Energy per shower]×[Showers per week]×52×[Energy price per kWh]
Example values
How the main result changes when Shower length changes and everything else stays at the example values above:
| Shower length (minutes) | Water per year (L) |
|---|---|
| 4 | 13,104 |
| 6 | 19,656 |
| 8 | 26,208 |
| 10 | 32,760 |
| 12 | 39,312 |
| 16 | 52,416 |
Formula
Water = minutes × flow rateEnergy = water × 4.186 kJ/kg·K × temperature riseWorked example
Inputs — Shower length: 8 minutes; Flow rate: 9 L/min; Showers per week: 7; Water heated by: 30 °C; Energy price per kWh: $0.18.
Results — Water per shower = 72 L; Energy per shower = 2.51 kWh; Water per year = 26,208 L; Heating cost per year = $164.56.
Frequently asked questions
What flow rate is typical?
Older showers 10–15 L/min; low-flow heads 6–8 L/min.
Does this include heater efficiency?
No; divide energy by your heater efficiency for a closer estimate.
What formula does the Shower Water and Energy Calculator use?
Water = minutes × flow rate.