Immersion Heater Not Working? Replacement Cost & Running Costs in 2026

Immersion heater not working? Quick answer and cost summary

If your immersion has stopped heating, the fix could be free (a reset) or could run into the hundreds (a new cylinder). Working out what failed before you call anyone is the difference between a £0 fix and a £200 bill.

Here is the 2026 cost picture at a glance, before we help you triage the fault. Figures are indicative UK ranges; always get a quote for your own job.

Job	Indicative fitted cost (2026)
Element-only swap	£130–£280
Thermostat-only replacement	£100–£170
New element + thermostat together	£180–£320
Full new hot-water cylinder (corroded/leaking)	£450–£900+

First, work out what has failed (triage before you pay)

Most "dead" immersions fall into a handful of patterns. Match your symptom below — it tells you whether to reset, or to budget for a part.

• Nothing at all, switch does nothing: check the consumer unit for a tripped MCB or RCD. Reset it once. A breaker that trips again the moment you switch on usually means an element earth fault — that element needs replacing.
• Was working, now stone cold: look for the overheat cut-out. There is a small reset button (often red or white) on the thermostat head, behind the round cover plate. Press it firmly until you feel a click.
• No hot water and the reset will not hold: most likely a burnt-out element. This is the single most common immersion failure.
• Lukewarm or slow to heat: usually a limescale-coated element (it insulates the element and wastes power) or a failing thermostat that cuts out too early.
• Trips repeatedly on reset: a live-to-earth fault in the element. Do not keep resetting it — replace the element.

If the cylinder is heated by your boiler rather than the immersion, the problem may sit on the heating side instead. See our guides on why an unvented cylinder isn't producing hot water and what to do when there's no hot water but the heating still works.

Repair or replace — element, thermostat or whole cylinder?

Once you know roughly what failed, the decision is usually simple.

• Replace the element and thermostat together. The parts are cheap and they share the same labour (the cylinder is drained and the head is off either way), so doing both at once avoids a second call-out later.
• Replace just the thermostat only if the element tests sound and the fault is clearly the stat cutting out early.
• Replace the whole cylinder if it is leaking, heavily corroded, foam-lagged and 15–20+ years old, or simply undersized for your household. At that age a new element in an old tank is throwing good money after bad.

Immersion heater replacement cost 2026 (the money table)

Parts are inexpensive; labour is the bulk of the bill. Here is the full breakdown — indicative ranges that vary by region, access and trade.

Item	Indicative 2026 cost
Copper element (part)	£20–£30
Incoloy element (part)	£25–£40
Titanium element (part)	£30–£45
Thermostat (part)	£10–£25
Labour (electrician/plumber)	£50–£80/hr, job 1–2 hrs
Many tradespeople: fixed price	£120–£180
Emergency / out-of-hours surcharge	+£80–£150

Putting that together: an element-only swap is typically £130–£280 fitted, an element-plus-thermostat job £180–£320, and many straightforward jobs land around £180 fitted. London and the South East typically add 20–35%. Always confirm the price with the tradesperson before work starts.

For context on how that compares with other repairs, see our typical boiler repair costs guide.

What affects the price

Two identical-looking jobs can differ by £100 once the engineer is on site. The usual culprits:

• Access. A tank boxed into a cramped airing cupboard takes longer to reach and work on.
• Draining. Many cylinders must be partly or fully drained to swap the element safely; that is dead time you pay for.
• A seized old element. Decades of corrosion can need a special box spanner and real muscle — sometimes the only way out is to replace the cylinder.
• Heavy scale. A scaled-up tank slows everything down and may justify a flush.
• Region. London and the South East are dearest.
• System type. Economy 7 dual-element vented cylinders are straightforward; an unvented cylinder is a Building Regulations G3 system and must be worked on by a suitably qualified (G3-registered) installer, which costs more.

Types of immersion element — buy the right replacement

If you are sourcing your own part, match it to your tank and water type.

• Length. Common sizes are 11", 14" and 27" (longer for tall, top-entry cylinders). It must reach near the bottom without touching it. Measure the old one.
• Single vs twin (dual). A twin-element cylinder has a long bottom element for cheap overnight heating and a short top "boost" element for daytime top-ups.
• Material:
  • Copper — cheapest, best for soft-water areas, typically lasts 5–10 years.
  • Incoloy — nickel-chromium alloy, resists scale and corrosion, around 10–15 years, fine in hard water.
  • Titanium — best in hard-water areas, resists limescale and corrosion, around 15–20 years and usually the most economical over time where the water is hard.

Immersion heater running costs in 2026

Here is where some competitors get it wrong (one widely-shared guide prints an absurd "£6,835/year" for a 3kW element — ignore it). The maths is simple: power (kW) × hours × unit price.

The July–September 2026 Ofgem price cap puts electricity at 26.11p/kWh on a single-rate tariff (the exact rate you pay varies by region, tariff and payment method). So a 3kW element uses 3 kWh per hour, costing about 78p per hour.

Usage (3kW element @ 26.11p/kWh)	Cost
Per hour	~78p
2 hours/day	~£1.57/day
Per month (2 hrs/day)	~£47
Per year (2 hrs/day)	~£570

Heating a full 120–160L tank from cold takes roughly 1.5–3 hours depending on size. A 6kW element heats twice as fast but costs the same per unit of heat delivered — it just front-loads the spend.

For how this stacks up against gas, see electric vs gas water heating running costs and how gas central heating running costs compare.

Slash the cost — Economy 7 and timers

The immersion's reputation as an expensive way to heat water comes almost entirely from running it on peak-rate electricity. Shift it off-peak and the picture changes.

• Economy 7 off-peak rates typically sit around 11–16p/kWh overnight (rates vary by supplier and region) — so a 3kW element drops to roughly 35–48p/hour, often around half the single-rate cost. Note that Economy 7 daytime (peak) units are usually dearer than the standard rate, so it only pays off if you shift most use to the night window.
• Dual-element cylinders heat the large bottom element overnight on the cheap rate, leaving the small top element for a quick daytime boost.
• An immersion timer or programmer (roughly £15–£60 fitted) automates the overnight window so you never heat on peak rate by accident.
• Set the thermostat to 60–65°C — hot enough to help control legionella, not so hot you scald or waste energy. There is no benefit to running it maxed out.
• Lag the tank with an insulating jacket so the heat you paid for at night is still there in the morning.

More wins in our guide on practical ways to cut your energy bill.

Should you keep the immersion at all, or move to your boiler?

If your immersion is a backup to a boiler-heated cylinder, keep it — it is cheap insurance for the day the boiler fails. Just check it works occasionally.

If it is your primary water heating and your bills sting, it may be worth costing a combi boiler or a heat pump, which can deliver hot water more cheaply per litre. That is a bigger decision and worth a proper quote rather than a rushed swap.

Is the immersion heater covered by boiler or central heating cover?

This is the question almost no cost guide answers — and it matters, because the right cover could turn a £200 bill into a £0 call-out.

• Boiler-only plans usually exclude the immersion heater and the hot-water cylinder entirely.
• Central-heating or "boiler & home" tiers may include the cylinder and immersion — but typically only if it is listed on your schedule. Read the policy document or plan terms; do not assume.
• Pre-existing faults, wear and limescale are common exclusions, so a long-failing element may not be claimable.

Cover terms differ between providers, so check the specific policy wording or plan terms before you rely on it. Our guides on central heating cover that can include the hot-water cylinder, what boiler cover typically excludes, and electric boiler and immersion cover explain what to look for.

How to find an engineer, and when it is an emergency

A standard immersion element or thermostat swap is electrical work — a qualified electrician (or a plumber who carries out the swap) is who you want. An unvented cylinder needs an installer with the relevant G3 qualification.

If the fault is on a boiler-fed cylinder — anything involving the gas boiler, burner, flue, sealed heating circuit, gas valve, PCB or pressure-relief valve — that is a Gas Safe registered engineer only. Never attempt that work yourself. You can check an engineer on the Gas Safe Register before they start.

If you ever smell gas or suspect a leak, call the National Gas Emergency line on 0800 111 999 immediately (free, 24/7).

This article is general information, not financial or gas-safety advice. We compare a selected panel of providers, not the whole market, and may earn a commission if you buy through our links. Always have gas appliances checked and repaired by a Gas Safe registered engineer; in a gas emergency call 0800 111 999. Prices are indicative UK guides for 2026 — confirm current prices on the provider's own site.