Cost guide
How much does boiler installation cost?
A combi boiler replacement costs £1,900 to £3,600 fitted. A system conversion, where a cylinder and loft tanks come out, runs £3,200 to £5,500. Labour is typically £700 to £1,400 of the total.
Typical prices
Ranges, not quotes. A quote depends on your room.
| Work | Typical UK price |
|---|---|
| Combi swap, same position | £1,900 to £3,600 |
| Combi swap, boiler relocated | £2,600 to £4,300 |
| Conventional to combi conversion | £3,200 to £5,500 |
| System boiler with unvented cylinder | £3,800 to £6,500 |
| Back boiler removal and replacement | £3,000 to £5,000 |
| Labour only, customer supplies boiler | £700 to £1,400 |
Get the mains flow rate measured before committing to a combi. It is a five minute test with a weir gauge and it is the single fact that decides whether the house will be happy with the boiler you are about to buy.
What moves the price
- Whether the boiler stays where it is. Moving it means new gas, water, flue and condensate runs.
- Brand and warranty length. A ten-year warranty boiler costs more up front and needs an annual service to stay valid.
- Whether the incoming water main needs upgrading to 22mm for a combi to perform.
- Removing a cylinder, loft tanks and the old vent pipework.
- Controls. A smart thermostat and TRVs add £200 to £500 and are now required on most new installs.
- System cleaning. A chemical flush is included on most quotes; a power flush is £350 to £700 extra.
What the money buys: swapping a combi boiler like for like.
Who quotes for it
20 of the 61 plumbers and heating engineers listed on this site take on boiler installation.
Most of them in one place: Birmingham (5), Leeds (4), Manchester (4), Glasgow (4), Liverpool (3).
Questions about boiler installation
What size boiler do I need?
Output is matched to the heat loss of the house and, for a combi, to the hot water demand. Most three-bedroom houses land between 24kW and 30kW. Oversizing wastes gas and makes the boiler cycle.
Is my old boiler worth repairing instead?
If parts are still available and the repair is under about a third of a replacement, repair usually wins. Once a boiler is past fifteen years and the heat exchanger is the problem, replacement is the cheaper answer over five years.