Immersion Heater

An electric heating element inserted directly into a hot water storage cylinder, used as a backup to or replacement for a gas boiler. Immersion heaters are common in properties without gas or as emergency hot water when a combi boiler fails. They are relatively expensive to run (typically 3 kWh per hour) but can heat a full cylinder of hot water in 1–2 hours. The element and thermostat can be replaced without changing the cylinder.