The instantaneous water heater CEX-U / CEX is a electronically controlled, pressure-resistant water heater for a decentralised hot water supply to one or more outlets. Its electronic control regulates the heating power consumption depending on the selected outlet temperature, the respective inlet temperature and the flow rate, thus reaching the set tem perature exactly to the degree and keeping it constant in case of pressure fluctuations. The required outlet temperature can be entered on a keypad and can be read off the digital display.