Shower Water & Energy Calculator
By Santaji GadepatilinUpdated October 27, 2026
Showers use water and the energy to heat it. Shorter showers and low-flow heads cut both bills and emissions. This free shower water & energy calculator solves for whichever value you leave blank and shows the formula and steps.
How to use the shower water & energy calculator
Enter the shower length, flow rate and showers per week. Water per shower, per year and the energy to heat it are calculated.
Example
8-minute showers at 10 L/min, 21 per week:
- 80 L per shower
- 87 m³ per year
- About 2,530 kWh a year to heat (25 °C rise)
Switching to a 7 L/min head cuts water and heating energy by 30%.
Water per shower
| Flow rate | 5 min | 8 min | 10 min | 15 min |
|---|---|---|---|---|
| 6 L/min | 30 L | 48 L | 60 L | 90 L |
| 8 L/min | 40 L | 64 L | 80 L | 120 L |
| 10 L/min | 50 L | 80 L | 100 L | 150 L |
| 12 L/min | 60 L | 96 L | 120 L | 180 L |
| 15 L/min | 75 L | 120 L | 150 L | 225 L |
Typical flow rates: low-flow heads 6–8 L/min, standard 9–12 L/min, power showers 15 L/min or more.
Shower vs bath
A typical bath uses about 80–150 L. A short shower with a low-flow head uses a fraction of that, but a long power shower can use more than a bath.
Saving water and energy
- Install a low-flow shower head — often cuts water by 30–50% without much change in feel.
- Cut shower time by 2 minutes.
- Lower the water heater setting slightly (keep it at least 60 °C in storage tanks to control Legionella).
- Fix dripping taps — see the water leak calculator.
Heating energy
Heating water takes about 4.186 kJ per litre per °C. Warming 80 L by 25 °C uses about 2.3 kWh. With an electric heater at 0.15 per kWh, that is about 0.35 per shower.
Frequently asked questions
How much water does a shower use?
About 8–12 litres per minute for a standard shower head and 6–8 for a low-flow head.
How much energy does heating shower water take?
Raising water by 25 °C takes about 0.03 kWh per litre — about 2.3 kWh for an 80-litre shower.
How do I measure my flow rate?
Time how long it takes to fill a 5-litre bucket. 30 seconds means 10 L/min.
How much water does a 10-minute shower use?
About 60–120 litres, depending on the shower head flow rate.
How do I measure my shower flow rate?
Time how long it takes to fill a 5 L bucket. If it takes 30 seconds, the flow is 10 L/min.