How much does it cost to replace a hot water cylinder in the UK?

A vented copper cylinder replacement (the traditional type fed from a cold water tank in the loft) costs £400–£900 installed. The cylinder costs £150–£400; labour is £250–£500 for an experienced plumber.

An unvented (pressurised) cylinder is fed directly from the mains and provides better pressure. Supply and installation costs £800–£2,000 depending on cylinder capacity and location. Unvented cylinders can only be installed by a G3-qualified engineer — this qualification adds to the labour cost but is a legal requirement.

Cylinder sizes are measured in litres. A 1–2 person home: 120–150L. Family of 3–4: 180–210L. Larger families or high-demand homes: 250–300L. Undersizing a cylinder is a common mistake — the extra cost of going one size up is small.

Heat pump compatibility: if you are planning to install a heat pump in future, choose a cylinder specifically designed for heat pump use — these have a large coil to work with the lower flow temperatures heat pumps produce. Cost is £50–£200 more than a standard cylinder.

Immersion heaters: most cylinders include an immersion heater as a backup. Replacing just the immersion heater element costs £80–£150 — useful if the cylinder is otherwise sound.

Indirect cylinders (heated by the boiler via a coil) are the standard for homes with a separate boiler. Direct cylinders (heated by an immersion only) are used where there is no boiler — less efficient for daily use.