When your hot water fails, a quick repair is a top priority. The cost of a water heater repair in the UK in 2025 can vary significantly based on the type of heater and the nature of the fault.
For electric immersion heaters, common issues include a faulty thermostat or a burned-out heating element. Replacing either of these parts is a relatively quick job for an electrician or plumber, and you can expect the total cost, including the part and labor, to be between £100 and £250.
For gas water heaters or combi boilers, repairs are generally more complex and expensive. A simple fix, like replacing a faulty thermocouple or pressure relief valve, might cost between £150 and £300. More complex issues, such as a problem with the gas valve or the heat exchanger, can be much more costly to repair, potentially ranging from £300 to £600 or more.
The plumber or engineer's labor rate is a major part of the cost. Expect to pay a call-out fee of £50-£100, plus an hourly rate of £50-£100. These rates will be higher for emergency, out-of-hours call-outs. The cost of the replacement parts will be added to the labor charge.
When deciding whether to repair or replace your water heater, a good rule of thumb is to consider its age. If your water heater is over 10 years old and the repair cost is more than half the price of a new unit, it is often more economical in the long run to invest in a replacement.
Crucially, any repairs to a gas appliance must be carried out by a Gas Safe registered engineer. For unvented hot water cylinders, the professional must hold a G3 qualification. Always verify their credentials before allowing them to start work.