Shower Cost Calculator
Cost and energy of one shower, the water used, and the yearly cost for a household.
Results
What this tool does
Two minutes less per shower, across three people every day, is the last result — usually a larger saving than anything the thermostat can do. A standard head runs at 9 to 12 litres a minute and a power shower at 15 or more, while an aerating head can halve that without feeling weaker. The temperature rise is from cold mains, so about 27 degrees in winter and less in summer.
Formula
energy = volume × 4.186 × ΔT ÷ 3600
Variables
| Symbol | Meaning | Unit |
|---|---|---|
mn | Minutes | min |
fl | Shower flow rate | L/min |
dt | Temperature rise | K |
pe | Price per kWh | — |
pw | Water price | /m³ |
np | Number of people | — |
CS | Cost | — |
EN | Energy | kWh |
VL | Volume | L |
CY | Total cost per year | — |
S2 | Cost | — |
Worked example
- Minutes8 min
- Shower flow rate9 L/min
- Temperature rise27 K
- Price per kWh0.18
- Water price1.8 /m³
- Number of people3
- Cost0.5365
- Energy2.2604 kWh
- Volume72.0 L
- Total cost per year587.44
- Cost146.86
Limitations
- The result is an estimate based only on the values you type. Real situations often include factors this calculator does not know about.
- The tool works with whatever currency you use for the inputs; it does not convert between currencies.
- The default values are typical reference figures, not measurements of your situation. Replace them with your own data whenever you have it.
Frequently asked questions
Where does the 4.186 come from?
It is the specific heat capacity of water in kilojoules per kilogram per kelvin — the energy needed to warm one litre by one degree. Dividing by 3600 turns kilojoules into kilowatt-hours. Water's heat capacity is remarkably high, which is why heating it dominates a household's energy bill and why the biggest saving in a shower is minutes, not degrees.