Estimate the energy and electricity cost of each shower from heater power, duration and daily use.
We multiply heater power by the duration of each shower, the number of daily uses and the number of days in the month.
A 7.5 kW unit uses 0.125 kWh per minute at full power. Cutting two minutes from each shower can make a visible annual difference.
The temperature reached depends on heater power, incoming water temperature and water flow.
Electric showers are high-power appliances, so every extra minute adds a noticeable amount of energy. A 7.5 kW heater uses 0.125 kWh for each minute it operates at full power, before multiplying that by daily showers and days per month.
The heater has to raise the incoming water to a comfortable temperature while water is moving through the unit. Colder inlet water or higher flow can require more heating effort, while reducing flow can change the outlet temperature.
This calculator estimates electricity only. Total shower cost also depends on litres used and the local water and wastewater tariff. If you are comparing habits, time a normal shower rather than relying on a rough guess.
For a worked cost example, read electric shower cost. For the general watts-to-kWh method, see how to calculate electricity consumption.
Editorial review: 11 Oct 2026. High-power fixed electrical equipment should be installed and checked by a qualified professional.
