You can count on less
Instantaneous water heaters heat the water directly at the point of use – and only when the water flows. That means in contrast to conventional storage heaters no hot water is stored. That avoids expensive heat losses. As a result instantaneous water heaters are more economic than conventional storage heaters, although they have a three-phase power connection. Electronically controlled instantaneous water heaters are particularly energy efficient, because they automatically adapt the power output to actual requirements.
The electronic instantaneous water heater CFX-U with a set power output of 11 kW (flow rage: 5 l/min at 45 °C) was compared with a 5-litre storage heater (standby power consumption 0.25 kWh / d at 65 °C) and a requisite mixed-water flow of 7.5 l/min in a three-person household with the following parameters: duration of use per person per day: two minutes: temperature at point of use: 45 °C; number of days in use: 340 days (source: CLAGE).