Water Heater Installation Cost
£300–£800
typical UK range
Updated
Installing a water heater in the UK costs £300–£800 for an electric immersion heater or small water heater. Hot water cylinders (unvented or vented) cost £800–£2,500 installed. Costs vary significantly by type, size, and whether you're replacing an existing unit or installing from new.
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How much does each option cost?
| Type / scope | Typical cost | Notes |
|---|---|---|
| Electric immersion heater replacementReplacing a faulty immersion heater element — 1–2 hours including draining down and electrical reconnection | £150–£300 | Replacing a faulty immersion heater element — 1–2 hours including draining down and electrical reconnection |
| Small point-of-use water heater (under-sink or over-sink)Supply and install of a 10–15L under-sink electric water heater; useful where there's no hot water supply point | £200–£500 | Supply and install of a 10–15L under-sink electric water heater; useful where there's no hot water supply point |
| Vented hot water cylinder replacement (like-for-like)Replacing an existing indirect vented cylinder with a new one in the same location; cylinder cost plus labour | £500–£1,200 | Replacing an existing indirect vented cylinder with a new one in the same location; cylinder cost plus labour |
| Unvented hot water cylinder (G3) installationUnvented cylinders provide mains-pressure hot water; higher specification, must be installed by a G3-qualified plumber | £1,000–£2,500 | Unvented cylinders provide mains-pressure hot water; higher specification, must be installed by a G3-qualified plumber |
| Thermal store hot water cylinderCombined heat store and hot water cylinder; often used with renewable heat sources; specialist installation | £1,200–£3,000 | Combined heat store and hot water cylinder; often used with renewable heat sources; specialist installation |
| Instantaneous (combi) water heater installationElectric flow-through water heater for instant hot water at a single point; requires adequate electrical supply | £300–£700 | Electric flow-through water heater for instant hot water at a single point; requires adequate electrical supply |
What affects the price?
- Type of water heater — point-of-use electric heaters are cheapest to install; unvented cylinders are the most expensive and require a G3-qualified plumber
- Replacement vs new installation — replacing an existing water heater in the same location is significantly cheaper than installing one where none existed
- Cylinder size — larger cylinders (200L+ for family homes) cost more in materials and take longer to install
- G3 qualification requirement — unvented cylinders must be installed by a qualified G3 plumber; this specialist skill commands a premium
- Whether electrical work is needed — some water heaters require electrical connection by a Part P electrician (additional cost)
- Location — London and South East rates are 20–30% higher than average
- Existing infrastructure — if new pipework or structural support is needed, costs increase
What's included in the price?
- Supply and installation of the water heater or cylinder
- Connection to hot and cold water supply
- Safety valve installation (unvented cylinders — mandatory)
- Expansion vessel and pressure relief valve (unvented)
- Thermostat and temperature control setup
- Testing and commissioning
- Building Regulations compliance notification (required for unvented cylinders under Part G)
- Handover instructions for safe and efficient use
How long does it take?
An immersion heater replacement takes 1–2 hours. A vented cylinder replacement takes 3–5 hours. An unvented cylinder installation takes 4–8 hours including all associated safety equipment and regulatory compliance. New water heater installations from scratch (where none existed before) may take longer depending on pipework requirements.
Do I need one?
You may need a new water heater if: your existing cylinder is more than 15–20 years old and developing leaks or corrosion; recovery time has significantly increased; energy bills have risen unexpectedly (older cylinders lose heat rapidly); or you're converting from a combi boiler back to a hot water storage system for high-demand applications. Unvented cylinders must be installed under Part G of the Building Regulations and must be inspected annually. Only G3-qualified plumbers may install unvented hot water storage systems.
How do you avoid overpaying?
- Replace a like-for-like cylinder in the same location to avoid additional pipework costs
- Consider whether your hot water demand justifies an upgrade to an unvented cylinder (mains pressure) — the higher install cost is offset by better performance in multi-bathroom homes
- A well-insulated modern cylinder loses significantly less heat than an older model — the energy savings partially offset the replacement cost over time
- Ask your plumber if your existing expansion vessel and safety valves can be reused — on a recent cylinder, this saves £100–£200
- Get multiple quotes for unvented cylinder work — G3-qualified plumbers vary in price
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Frequently asked questions
We’re happy to answer all your questions.
How much does it cost to install a hot water cylinder in the UK?
A vented hot water cylinder replacement costs £500–£1,200 installed. An unvented (mains pressure) cylinder costs £1,000–£2,500. A small point-of-use electric water heater costs £200–£500 installed. Costs vary with cylinder size, type, and the complexity of the installation.
What is an unvented hot water cylinder?
An unvented cylinder stores hot water at mains pressure, providing a powerful flow at all outlets simultaneously — ideal for homes with multiple bathrooms. Unlike a traditional vented cylinder (which uses gravity pressure from a cold water tank in the loft), an unvented cylinder connects directly to the mains. It must be installed by a G3-qualified plumber due to the safety requirements of pressurised hot water storage.
Do I need a G3 certificate for a hot water cylinder?
G3 certification is required for the installation of unvented hot water storage systems. The installer must be G3-qualified, and the installation must be notified to Building Control under Part G of the Building Regulations. Vented cylinders do not have this requirement but should still be installed by a qualified plumber.
How long does a hot water cylinder last?
A well-maintained hot water cylinder typically lasts 20–30 years. Unvented cylinders with annual servicing of safety valves can last 20–25 years. Signs of end-of-life include corrosion or pinhole leaks, significantly increased heat loss (cold water within hours of heating), or heavy limescale buildup in hard water areas.
Sources & References
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