Formula and example
How it is calculated
Litres per shower = flow rate × minutes; annual volume = litres × showers per week × 52
Worked example
9 l/min for eight minutes uses 72 l per shower. Seven showers per week use 26.208 m³ over 52 weeks.
Things to check
- Energy for hot water and standing charges are excluded. You can measure flow rate with a bucket and a stopwatch.
- Use one currency consistently. Examples use euros; the calculation works with any currency.