How much does a new boiler cost in 2026?

We do not publish a price for a new boiler, and there is a good reason for that. A number on a page becomes the number you expect, and the installer who has actually stood in your house then has to argue with it. What we can do is tell you what the price is made of, so you can read a quote and judge whether it is fair.

A straight combi swap in the same position is the cheapest version of the job. Replacing a system boiler and keeping the cylinder sits above it. Converting a conventional system to a combi, where the cylinder and loft tanks come out, is the most expensive by a clear margin. The boiler itself is often the cheaper half of any of them: the rest is labour, parts and the awkwardness of your particular house.

What are you actually paying for?

A quote that is one line and one number is hiding four separate costs. Any installer will break them down if you ask, and the ones who hesitate are usually the ones worth avoiding.

• The boiler itself, at trade price rather than the RRP you see online, which almost nobody pays.
• Labour. One day for a straight swap, two or three for a conversion. London and the south east run noticeably higher than the north.
• Parts and controls. Flue, filter, thermostat, and the chemical flush.
• The extras that are easy to miss: scaffolding if the flue is high up, a new gas supply pipe if the existing one is too narrow, making good the plasterwork.

Why do two quotes for the same job differ by hundreds?

Because they are usually not the same job. The most common reasons, in rough order of how often they come up:

• A different boiler. A 12-year warranty premium brand against a 5-year budget one is a real swing on its own, before anyone picks up a spanner.
• One quote includes a system flush and the other does not. A proper power flush is one of the larger lines on any quote and it is genuinely necessary on an old, sludgy system. A chemical flush is cheaper and often enough on a newer one.
• One installer has spotted that your gas supply pipe is 15mm and a modern combi needs 22mm. That is a real cost and the quote that ignores it will become a variation later.
• A magnetic filter, a new thermostat, or new radiator valves included in one and not the other.
• VAT. Some smaller installers are not VAT registered, which makes them 20% cheaper on paper for the same work.

What does the law require, and does it cost extra?

Since Boiler Plus came in, a new gas boiler fitted in England has to be at least 92% ErP efficient and must be installed with at least one additional energy-saving measure. In practice that usually means a smart thermostat, load compensation or flue gas heat recovery.

This is not an upsell. If a quote does not mention any of them, ask which one is being fitted, because the installation is not compliant without it. It is also why a like-for-like swap of a fifteen-year-old boiler still comes with controls you did not have before.

All gas work must be done by a Gas Safe registered engineer, and the installation must be notified to Building Control, which your installer does through Gas Safe. You should receive a Building Regulations Compliance Certificate afterwards. If you do not, chase it, because you will want it when you sell the house.

Source: Gas Safe Register; Building Regulations Approved Document L

Is a cheaper boiler a false economy?

Not always, but the warranty is where the difference shows. Budget boilers typically come with 2 to 7 years. Premium brands offer 10 to 12, and occasionally more.

Two things to know about those long warranties. They usually require the boiler to be registered within 30 days and serviced annually by a Gas Safe registered engineer, with the paperwork kept. Miss a service and the warranty can be void. And the longest warranties are often only available when the boiler is fitted by an installer accredited by that manufacturer, which is a question worth asking before you choose.

Spread across twelve years, a price difference between two boilers comes down to very little each year. If it buys you a warranty that would actually cover a heat exchanger failure in year eight, which is the dearest part in the boiler, it is cheap. If it buys you a badge, it is not.

How much will it save on your bills?

Replacing an old, inefficient boiler with a modern condensing one can save a household up to around £840 a year, depending on the property and the boiler being replaced. That figure is a market average from the Energy Saving Trust, not a promise about your house.

The honest version: the savings are largest when you are replacing something genuinely old and inefficient, in a larger detached home, and smallest when you are swapping a ten-year-old combi that still works. Anyone who tells you a new boiler pays for itself in three years does not know your house.

Source: Energy Saving Trust

How do you avoid overpaying?

Get three quotes, in writing, and make sure each one lists the boiler make and model, what flushing is included, whether the gas supply pipe is being upgraded, and what the warranty is.

Then compare them line by line rather than on the headline number. The cheapest quote that omits a required gas pipe upgrade is not the cheapest quote, it is the one that will change price halfway through the second day.