Immersion Heater Replacement Costs UK — What to Charge to Fit One in 2026

What an Immersion Heater Replacement Actually Involves

An immersion heater is an electric element that screws into a hot water cylinder — usually through a 2¼" BSP boss — and heats the stored water directly, controlled by a thermostat. On most jobs the customer says "my immersion has gone", but the actual fault could be the element, the thermostat, or the wiring at the connection. Diagnosing which it is before you quote saves you from charging for a full element swap when a £15 thermostat would have done.

A straightforward replacement means isolating the supply, draining enough of the cylinder to drop the water level below the boss, unscrewing the old element with an immersion spanner, fitting a new element with fresh fibre washer and PTFE, refilling, and re-wiring and testing. On a healthy cylinder that's an hour's work. The trouble is that "healthy cylinder" assumption — and it's the assumption that catches operators out.

Immersion Heater Replacement Costs in 2026

Replacing the Element Only

This is the most common job. The element itself is cheap — a standard Incoloy element runs £20–£60 depending on length and brand (Backer, Tesla and Cotherm are the common names; budget no-brand elements exist but are a false economy on a job you'll want to guarantee). Labour is typically 1–2 hours including draining and refilling.

• Element swap, supply and fit, all-in: £120–£250
• Element part cost: £20–£60
• Labour: 1–2 hours

Price toward the top of that range where access is awkward, where the cylinder needs a full or partial drain-down, or where the element is likely to be seized. A loft-mounted cylinder, a boxed-in airing cupboard, or a property with no convenient drain point all push the time up.

Replacing the Thermostat Only

If the element tests fine but the thermostat has failed, you're only changing the stat — a part costing £10–£25 that slides into the element pocket and clamps in place. No draining required. This is a sub-30-minute job for a competent operator, and most trades charge a minimum call-out or a fixed £60–£100 for it rather than billing it as a full element swap. Be honest here: charging element-swap money for a thermostat change is the kind of thing that ends up on a review site.

Fitting a New Immersion to a Cylinder That Didn't Have One

Occasionally you're asked to add immersion heating to a cylinder that only had a coil from the boiler — for example as a backup when the boiler is on its last legs. If the cylinder already has a spare boss, this is a clean element fit plus first-time wiring. If there's no spare boss, the cylinder can't take one and you're into a cylinder replacement conversation. Where a spare boss exists, the labour is similar to a standard swap but you'll add the cost of running a new circuit (covered below).

The Seized-Element Risk — Where Money Is Lost

This is the single biggest reason immersion jobs go over time. On an old cylinder, the element threads corrode into the boss. You apply the immersion spanner, lean on it, and one of three things happens: it comes free (good), it won't budge (frustrating), or — worst case — the element body shears off and you're left with a threaded ring corroded into the cylinder boss.

A seized element can turn a one-hour job into a half-day. The standard escalation is heat, penetrating oil, a longer breaker bar, and a proper immersion spanner rather than a strap wrench. If it still won't move, or if the element snaps, you're often at the point of recommending a new cylinder — because forcing it risks splitting the cylinder boss entirely and turning a hot-water job into a flood.

Protect yourself in the quote. Never promise a fixed element-swap price on a cylinder you suspect is 20-plus years old without a clause: something like "price assumes the existing element can be removed without damage to the cylinder; if the element is seized or the cylinder is found to be unserviceable, replacement of the cylinder will be quoted separately." That one sentence is the difference between absorbing a half-day's loss and being paid for the work you actually do.

When to Recommend a New Cylinder Instead

Sometimes the right call is not to fight the old element at all. If the cylinder is heavily corroded, weeping at the boss, decades old, or the element has already sheared, replacing the whole hot water cylinder is the honest recommendation. A supplied-and-fitted vented copper cylinder typically runs £500–£1,200 depending on size, type and how much pipework needs reworking. Unvented cylinders are more — and require a G3 qualification to install, so don't quote one unless you hold it.

• New hot water cylinder, supplied and fitted: £500–£1,200
• Cheaper single-coil vented copper cylinders sit at the lower end
• Larger, twin-coil or unvented units (G3 required) sit above this range

Framing matters when you have this conversation. A customer who called expecting a £150 fix will not love hearing "£900 for a cylinder" — so explain it in terms of risk and value: a new cylinder comes with a fresh element and thermostat, restores efficiency, and removes the corrosion that caused the failure in the first place. Show them the seized element if you've already got it out. Evidence sells the upsell.

Wiring an Immersion Circuit — The Electrical Side

An immersion heater draws around 13A on a 3kW element, and the regulations require it to be supplied by its own dedicated circuit — not spurred off a ring final or shared with anything else. That means a connection back to the consumer unit on appropriately rated cable, typically 2.5mm² heat-resisting flex from the switch to the element, and a double-pole switch (commonly a 20A DP switch with a flex outlet, or a dedicated immersion switch) so both line and neutral are isolated for safe servicing.

On a like-for-like element swap, the wiring is usually already in place and you're just re-terminating into the new element — no extra circuit cost. The cost arrives when there's no existing supply (the "add an immersion" scenario) or the existing wiring is unsafe. Running a new dedicated circuit from the consumer unit, fitting the DP switch and heat-resisting flex, and testing and certifying it is a separate electrical job — budget a half-day plus materials, and it must be Part P notifiable work, so factor in your registration and certification.

On Economy 7 systems, watch for dual-element cylinders: a long bottom element on the off-peak (night) circuit heating the full tank, and a short top element on a boost circuit for daytime top-ups. These are wired to a timer or an Economy 7 meter, and if you replace one element you need to confirm you've matched the right length and re-wired to the correct circuit. Quote dual-element cylinders as two elements' worth of parts and add time for the extra draining and wiring care.

What Affects the Price

Two element swaps can be £130 apart for reasons that have nothing to do with the part. Before you quote, weigh these factors:

• Access: A cylinder in an open airing cupboard at waist height is fast. One boxed in, in a loft, or behind a bath panel adds time before you've touched a spanner.
• Seized element: The big one. An old, corroded cylinder carries real risk of the element snapping or the boss splitting. Price in the possibility or caveat it.
• Cylinder condition and age: A weeping, ancient cylinder may not be worth fixing — and refilling it could reveal leaks that weren't there before.
• Draining and refilling: If there's no drain cock or convenient outlet, draining the cylinder properly adds time. Some jobs only need a partial drain to drop below the boss; others need a full drain.
• Economy 7 / dual elements: Two elements, two circuits, more care — more time and parts.
• Wiring: Like-for-like is free; a new dedicated circuit with DP switch and certification is a separate job.
• Out-of-hours: No hot water is an emergency to most customers. An evening or weekend call-out carries a premium — typically 1.5× to 2× your standard rate, or a fixed emergency call-out fee on top.

Supply-and-Fit vs Labour-Only

Decide upfront whether you're pricing supply-and-fit or labour-only. Supply-and-fit — where you provide the element, washer, PTFE and any sundries — is the cleaner model: you control the part quality, you mark up the materials (a perfectly normal trade practice), and you carry one clear warranty for the whole job. This is how most trades should quote it.

Labour-only, where the customer has bought their own element off the internet, is worth being cautious about. You've no control over the part, the warranty position gets murky if their cheap element fails in six months, and you may find it's the wrong length for the cylinder. If you do labour-only, charge your full labour rate and make clear in writing that the part is the customer's responsibility and not covered by your guarantee.

Day Rate vs Fixed-Price Quoting

For a single immersion swap, most customers want a fixed price, not a day rate — they want to know the number before they say yes. A straightforward like-for-like swap is best quoted as a fixed £150–£250, which covers your part, an hour or two of labour, and a modest contingency for a slightly stubborn element.

Where you fall back on a day rate is when the job is uncertain — a seized element, a suspect cylinder, or wiring work bundled in. A qualified plumber or electrician's day rate sits at £200–£300 per day in most of the UK (higher in London and the South East). If you genuinely don't know whether the element will come out, it's sometimes fairer to both sides to quote a fixed price for the swap with a clear caveat, and a separate day-rate or fixed quote for the fallback (new cylinder), rather than padding the fixed price so heavily that you lose the job to a cheaper rival who hasn't thought it through.

Quoting Tips — How to Price This Job Properly

• Diagnose before you quote. Establish whether it's the element, the thermostat or the wiring. Charging for an element when it's a £15 stat is how you lose repeat custom.
• Ask the cylinder's age. Over the phone, ask how old the cylinder is and whether it's ever been touched. An honest "it's the original from the 90s" tells you to caveat the seized-element risk.
• Caveat seized elements in writing. One clause protects a half-day of your time. Always include it on old cylinders.
• Quote the cylinder fallback alongside the swap. Give the customer both numbers upfront so the bad news isn't a surprise on the day.
• Separate the wiring. If a new circuit and DP switch are needed, line-item it. Customers understand notifiable electrical work is its own job.
• Set an emergency premium and stick to it. "No hot water" on a Sunday is worth a clearly stated out-of-hours rate — agree it before you travel.
• Mark up your materials. Supply-and-fit lets you do this cleanly and keep one warranty for the whole job.

Quick Reference: Immersion Heater Prices UK 2026