What this calculator does
Cost of a shower works out water and water-heating energy cost for one shower. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaWater cost = volume × water price; heating energy = volume(kg) × 4.186 kJ/kg·K × temperature rise ÷ 3600 ÷ heater efficiency
The inputs explained
| Field | What to enter |
|---|---|
| Shower length (minutes) | A number, measured in minutes. Starts at 8. |
| Flow rate (L/min) | A number, measured in L/min. Starts at 8. |
| Water price ($/1000 L) | A number, measured in your currency/1000 L. Starts at 2.5. |
| Electricity price ($/kWh) | A number, measured in your currency/kWh. Starts at 0.3. |
| Temperature rise needed (°C) | A number, measured in °C. Starts at 25. |
| Water heater efficiency | A number. Starts at 0.9. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with shower length
Every other input is held at the calculator’s starting values while shower length varies. Select any row to load that scenario into the calculator.