Where the money actually goes in a boiler quote
A line-by-line breakdown of a typical £2,500 installation, so you can read a quote properly and spot what has been left out.
14 July 2026 · 5 min read
Two quotes, both £2,500, can be completely different jobs. Here is roughly where the money goes on a typical combi swap, so you can compare like with like.
The boiler: £700 to £1,600
Trade price, not the RRP you see online. A mid-range 30kW combi is around £900 to £1,200. A premium brand with a 10-year warranty is more.
Installers buy at trade and mark up, which is entirely normal and how they make a living. What matters is the total, not the mark-up.
Labour: £500 to £1,200
One or two days for one or two engineers. Higher in London and the south east. This is the number that varies most by region and by how busy they are.
Flue and fittings: £100 to £300
More if the flue run is long, goes through a roof, or needs a plume kit because it would otherwise vent onto a neighbour's window.
System flush: £100 to £500
A chemical flush is the cheap end. A full power flush on a sludged-up system is the expensive end. This is one of the most common places for two quotes to diverge, and the cheaper one is not always wrong - it depends on the state of your system.
Magnetic filter: £80 to £150
Required by most warranties now. If it is not on the quote, ask why.
The extras that appear later
New radiator valves. A new thermostat, and whether it is a smart one. Making good the plasterwork. Removing the old cylinder and tanks on a conversion. Scaffolding, occasionally, for a flue on a high wall.
None of these are scams. All of them are things a vague quote can quietly exclude.
How to compare two quotes properly
Line them up side by side and check four things: same boiler model, same flush, filter included, warranty length. Once those four match, you are comparing prices rather than guessing.