The invention relates to a construction of accumulative combined heater of flowing through water and possibilities to heat water by various power sources. The proposed water heater comprises a tank (1) suitable for connecting to a water-supply line (10) or a heated water-feeding equipment or outer heating network (15). The novelty is that a heat exchanger (6) having an inlet (7) and an outlet (11) arranged outside of the tank (1) is placed in an inner space (5) of the tank (1). The inlet (7) is connected to the water-supply line (10) through a feeding unit (9). The space (5) of the tank (1) also is connected to the feeding unit (9).
