A liquid heater is described including a chamber for receiving a liquid, pairs of electrodes located within the chamber for applying electric current to the liquid, input terminals for connection to a power supply, a plurality of bridge arms connected in parallel to the input terminals, and a control unit for controlling switches of the bridge arms. The plurality of bridge arms include a respective bridge arm for each pair of electrodes and a common bridge arm, and each bridge arm includes a pair of switches and a node located between the switches. A first electrode of each pair of electrodes is connected to the node of the respective bridge arm, and a second electrode is connected to the node of the common bridge arm. The switches have a plurality of different states for selectively connecting pairs of electrodes to the input terminals in one of a plurality of electrode configurations, the electrodes having a different total electrical resistance in each electrode configuration.