How long should an unvented stainless steel immersion heater last

A good quality immersion heater fitted to an unvented stainless steel hot water cylinder will typically last 5 years though many last a lot longer, although its lifespan depends on several factors, including water quality, usage and whether it has been installed correctly. In hard water areas, limescale can build up on the heating element. This acts as an insulator, making the immersion heater work harder and reducing its efficiency, which can shorten its life. Frequent heating cycles and poor electrical connections can also contribute to premature failure. Signs that an immersion heater may be reaching the end of its life include: The water takes much longer than normal to heat up. The water never gets fully hot. The immersion heater repeatedly trips the electrics. There is no hot water at all. The thermostat frequently cuts out or fails. It's worth remembering that the thermostat is a separate component from the heating element. If your water isn't getting hot, the thermostat may simply need replacing rather than the entire immersion heater. If your immersion heater is over 15 years old and has started to become unreliable, replacing it is often more cost-effective than repeatedly diagnosing intermittent faults.