Replacing a water heater is a common home maintenance task. The total cost of installation in the UK in 2025 will depend on the type of water heater you choose and the complexity of the installation.
For a standard electric immersion heater replacement in an existing hot water cylinder, the cost is relatively low, typically ranging from £150 to £300, including the part and labor.
If you are replacing the entire hot water cylinder, the cost will be higher. A standard vented cylinder replacement can cost between £500 and £900, while a more modern, energy-efficient unvented cylinder will cost between £1,000 and £2,000 to supply and install. Unvented systems provide better water pressure but are more complex to fit.
For homes with a gas supply, replacing a gas storage water heater will typically cost between £800 and £1,500. A more popular option is a combi boiler, which provides both hot water and central heating. Replacing an old combi boiler with a new one costs, on average, between £2,500 and £4,500.
The main cost factors are the price of the unit itself and the labor involved. If the new water heater is a like-for-like swap in the same location, the labor costs will be lower. If you are changing the type of system (e.g., from vented to unvented) or moving the unit to a new location, the plumbing work will be more extensive and therefore more expensive.
It is crucial that any work involving gas is carried out by a Gas Safe registered engineer. For unvented cylinders, the installer must have a specific G3 qualification. Always check a professional's credentials before hiring them.