# Shower cost and water-saving calculator | EcoBack

> Estimate shower water and energy costs using measured flow, duration and your tariff. Compare a lower-flow showerhead and check compatibility first.

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## Calculate with your own values
Defaults are illustrative scenarios, not current tariffs or measured savings. Use one currency for every amount; no exchange-rate conversion. Units are litres, °C and kWh.

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## Method and example
Heat = litres × temperature rise × 0.001163 kWh; input energy = heat ÷ system factor. Add variable water and wastewater cost. Example: 12 litres/minute × 8 minutes = 96 litres; 10 to 38 °C requires 3.126144 kWh of heat. With factor 1, energy at 0.35/kWh and water at 5/m³, cost is about 1.57 per shower; at 8 litres/minute, about 1.05.

## Measure what comes out
If safe, collect water at your normal shower setting for a timed interval. Litres collected divided by seconds, multiplied by 60, gives litres per minute. Avoid burns and slippery floors. Repeat the measurement: supply pressure and settings affect it. A nominal product flow is not necessarily the flow in your bathroom.

## Use the right energy factor
Heat demand equals litres × temperature rise × 0.001163 kWh. Divide by useful heat delivered per unit of input energy. A factor of 1 is an illustrative direct-heating case, not a measured system efficiency. Use an appropriate factor for the actual equipment; hot-water heat-pump performance is not necessarily its space-heating rating. Distribution and storage losses are excluded.

## Check compatibility before reducing flow
Some instantaneous water heaters require minimum flow, and low-pressure arrangements may restrict which fittings can be used. Read both showerhead and heater instructions. Do not lower stored-water temperature or alter hygiene cycles because this calculator uses a lower mixed shower temperature; those are different settings.

## Compare variable costs honestly
Enter only the variable water, wastewater and energy rates in one currency. Standing charges remain outside the calculation. Equal duration and mixed-water temperature are assumed. If a lower flow makes you shower longer, update the minutes too. Payback does not include installation, maintenance or financing.

## Common questions
Does mixed shower temperature set the storage tank?No. Mixed outlet temperature and safe hot-water storage are different. Follow system hygiene requirements.
Can a water-saving head fit any heater?No. Minimum-flow and fitting requirements must be checked for the actual system.

## Sources and limits
Technical sources below are in German, checked for the original guide on 4 October 2026. These adaptations do not establish local rental law, installation rules or tariffs. Follow local requirements and the instructions for your actual system.

- co2online: Sparduschkopf und Durchlauferhitzer (DE)
- Verbraucherzentrale: Warmwasser und Hygiene (DE)

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