How this saving is worked out: CAR assumes that each household takes two showers a day, that an average shower lasts seven minutes, uses eight litres a minute and has a temperature of 41C. It says four-minute showers would save an average of 24 litres of hot water, resulting in an energy saving of 1.1 kWh per shower, or around 800 kWh per year for a household. CAR also estimated that a low-flow shower head would save an average of 28 litres of hot water, resulting an energy saving of 1.3 kWh per shower, or around 950 kWh per year for a household.