Cost guide
How much do hot water cylinders cost?
An unvented cylinder installation costs £1,800 to £3,500 fitted. Replacing a vented cylinder like for like is £700 to £1,400, and an immersion heater change is £150 to £300.
Typical prices
Ranges, not quotes. A quote depends on your room.
| Work | Typical UK price |
|---|---|
| Unvented cylinder, supply and fit | £1,800 to £3,500 |
| Vented cylinder replacement | £700 to £1,400 |
| Immersion heater and thermostat | £150 to £300 |
| Annual unvented cylinder service | £90 to £160 |
| Expansion vessel replacement | £180 to £350 |
| Cylinder with heat pump coil, supply and fit | £2,200 to £4,000 |
Ask to see the G3 qualification, which is a separate ticket from Gas Safe registration. Unvented cylinder work by somebody without it is unlawful and the installation will not be notified.
What moves the price
- Unvented against vented. Unvented needs G3 certified installation, a discharge route and building control notification.
- Cylinder size and whether it carries one coil or two.
- Whether a loft tank and vent pipework are being removed.
- The discharge pipe run to a safe visible termination outside.
- Whether the incoming main can supply the flow rate an unvented cylinder needs.
- A heat pump coil, which costs more now and saves a cylinder change later.
What the money buys: unvented cylinder installation and g3 certification.
Who quotes for it
Questions about hot water cylinders
What size cylinder do I need?
Roughly 150 litres for one bathroom, 210 litres or more for two in simultaneous use. A cylinder fed by a heat pump needs a larger coil than one fed by a boiler.
Can I keep my immersion heater as a backup?
Yes, and it is worth doing. Most cylinders take one or two immersion heaters, and they cover a boiler breakdown in the middle of winter.