Immersion Heater Replacement Cost (2026)
The immersion heater is the simplest heat source in the house — a kettle element in your cylinder — and its repair pricing is correspondingly tidy. What complicates the picture is water hardness, which decides whether your element lasts twelve years or two, and occasionally the electrics feeding it. The 2026 numbers, and the decisions attached to them:
Element and thermostat pricing
A standard immersion element replacement typically runs £90–£180 including the part — drain-down (or wet-change where the cylinder design allows), old element out with the correct immersion spanner, new element sealed and torqued, rewired at the head, tested. A thermostat-only replacement lands £70–£120. Combined element-and-stat, the sensible default when either fails on an older install, sits £110–£200. Unvented cylinders can add cost where access and G3 considerations apply.
The hard-water element decision
In hard-water areas, scale jackets the element, forcing it to run hotter for the same output — which is both your electricity bill and the element's early death. A basic copper element in hard water commonly lasts 2–5 years; an incoloy or titanium-sheathed element costs £15–£40 more and lasts substantially longer. In soft-water regions the basic element is fine for a decade or more. This is the rare plumbing upgrade with clean payback arithmetic: in hard water, always specify the better element.
When the fault is the electrics
An immersion draws around 13 amps continuously — real current through decades-old flex and switches. Scorching at the isolator, a warm switch plate, or repeated tripping that survives a new element all point at the circuit rather than the heater. That's electrician territory, and a plumber who reconnects a new element onto heat-damaged wiring is doing you no favour. Budget the possibility: a replacement isolator or flex outlet is modest money against the alternative.
Running-cost context
Per unit of heat, an immersion on standard-rate electricity costs more than gas-heated water — its economic role is backup heating and off-peak duty. On time-of-use tariffs, heating the cylinder overnight changes the arithmetic entirely, and a £15 timer or smart switch is the cheapest efficiency upgrade in this whole category. If the immersion is your only water heating, tariff choice matters more than any hardware in this guide.
| Job | Typical cost | Notes |
|---|---|---|
| Element replacement | £90–£180 | Incl. part; drain-down typical |
| Thermostat replacement | £70–£120 | Includes safety cut-out stats |
| Element + stat together | £110–£200 | Sensible default on older installs |
| Upgraded incoloy/titanium element | +£15–£40 | Hard-water areas: always |
How to use these price bands
Treat the ranges above as calibration, not quotation: your job sits somewhere in the band depending on access, parts and region, and a written quote from a vetted engineer is the only number that binds anyone. The practical use of national bands is spotting outliers — a quote far above the range deserves a written justification, and one far below usually has the missing money hiding in exclusions. Ask what's included, how extra time is charged, and whether parts are cost or cost-plus, and the band does its job.
Frequently asked questions
Why does my immersion keep tripping the RCD?
A breaking-down element leaking current to earth, almost always — the RCD is doing its job. Repeated resetting turns a safe fault into an unsafe one; isolate and replace the element.
How long does replacement take?
Typically 1–2 hours including drain-down. Top-entry elements above the waterline, or wet-change-suitable cylinders, can be quicker.
What temperature should the immersion be set to?
60–65°C — hot enough for hygiene, controlled enough for safety. Scalding output usually means a failed thermostat, which modern stats back up with a safety cut-out.
Is it worth having two immersion elements?
Twin-element cylinders (boost + off-peak) suit time-of-use tariffs well — the lower element heats the full cylinder overnight cheaply, the upper boosts a usable amount fast at standard rate.
Where this guide's advice ends
Written guidance has a natural limit: it can tell you what usually causes a symptom, but only eyes on your actual pipework can confirm it. If what you're seeing doesn't quite match any pattern described here, or matches several at once, that ambiguity is itself diagnostic information worth giving an engineer. Our vetted local plumbers do this triage daily — and an honest one will tell you on the phone if your problem sounds like a cheap fix, a bigger job, or (occasionally) not a plumbing problem at all.