The honest answer to “how much does a new boiler cost?” is that it depends on the boiler you choose, the size of your home and how much work the installation involves. As a rough guide, most UK homeowners pay somewhere between £2,000 and £4,500 for a new boiler fully installed, with straightforward like-for-like swaps at the lower end and bigger or more complicated jobs at the top.
That is a wide range, and it is wide for a reason. Two houses on the same street can need very different installations. One might be a simple combi swap done in a day. The other might need the boiler moved, a new flue run and a full system flush.
This guide walks through what actually drives the price, so you can read any quote with confidence. And if you are in Cornwall or Devon, DCI Boilers will give you a fixed price up front, so the number you agree is the number you pay.
What drives the cost of a new boiler?
Five things account for most of the difference between a cheap installation and an expensive one.
1. The type of boiler
Combi boilers heat water on demand and need no tank or cylinder, which usually makes them the cheapest to install. System boilers work with a hot water cylinder and suit homes with more than one bathroom. Regular (heat-only) boilers use both a cylinder and a loft tank, and tend to appear in older properties. Changing from one type to another costs more than replacing like for like, because pipework, cylinders and tanks may need to be added or removed.
2. The size of the boiler
Boiler output is measured in kilowatts (kW). A small flat might only need 24kW, while a large four-bedroom house with two bathrooms could need 35kW or more. Bigger boilers cost more to buy, but fitting an undersized one is a false economy. It will struggle on cold mornings and wear out faster. A good installer sizes the boiler to your home, not to the price list.
3. Whether the boiler is moving
Keeping the new boiler where the old one sits keeps costs down. Moving it, say from an airing cupboard to the kitchen, or from the kitchen to the garage, means extending gas, water and condensate pipework, and often a new flue route. Relocation can add a meaningful amount to the bill, so it is worth asking whether the move genuinely improves your home or is just a nice-to-have.
4. The flue
A simple horizontal flue through the wall behind the boiler is the cheapest option. If the flue has to run vertically through the roof, needs extensions, or must be repositioned to meet current regulations on distances from windows and boundaries, the price rises. Older installations often fail modern flue rules, and a proper quote accounts for bringing everything up to standard.
5. Controls and extras
Modern installations usually include a wireless or smart thermostat, and building regulations require certain efficiency measures such as a system cleanse and a magnetic filter to protect the new boiler. Smart controls, thermostatic radiator valves and a full power flush all add cost, but they also cut running costs and protect the manufacturer warranty, so they tend to pay for themselves.
Typical price ranges as a rough guide
Treat these as broad estimates rather than promises, because every home is different:
| Job | Typical range (installed) |
|---|---|
| Like-for-like combi swap | £2,000 to £3,000 |
| Combi swap with relocation or flue work | £2,500 to £4,000 |
| System or regular boiler replacement | £2,500 to £4,500 |
| Conversion to a different boiler type | £3,000 to £5,000+ |
The brand and model you choose matters too. Premium boilers cost more up front but often carry longer warranties. DCI Boilers installs boilers with up to 12 year manufacturer warranties, which changes the maths considerably. A boiler guaranteed for over a decade costs far less per year of cover than a budget model with a short warranty.
If your home runs on oil rather than mains gas, which is common across rural Cornwall and Devon, the picture is a little different. Our guide to oil boiler replacement covers what to expect.
Why a fixed quote beats guesswork
Online calculators and national averages can only ever guess at your home. They cannot see your flue position, your pipework, your water pressure or the state of your radiators. That is why estimates gathered online so often bear little resemblance to the final bill, and why “from” prices in adverts rarely survive contact with a real house.
A fixed quote for a gas boiler replacement works differently. An engineer looks at your actual system, sizes the boiler properly, spots the complications before the job starts and gives you one number. At DCI Boilers that number is fixed up front. No hourly drift, no surprise extras on the invoice, no awkward conversation at the end of the job.
It is also worth remembering that installation quality matters as much as the boiler itself. A well-fitted mid-range boiler will outlast a badly fitted premium one. All DCI Boilers engineers are Gas Safe registered for gas work and OFTEC registered for oil, so the installation is done properly and your warranty stays valid.
Should you repair instead of replace?
Not every struggling boiler needs replacing. If yours is under ten years old and the fault is minor, boiler repairs are often the sensible choice. Replacement starts to make sense when the boiler is old, inefficient, out of warranty and breaking down repeatedly, or when parts are becoming hard to find. An honest engineer will tell you which side of the line you are on. Once a new boiler is in, annual boiler servicing keeps it efficient and keeps the warranty intact.
How DCI Boilers can help
DCI Boilers installs, services and repairs boilers across Cornwall and Devon, from our base near Saltash. Every gas boiler replacement starts with a proper survey and ends with a fixed, upfront price, and we install boilers backed by up to 12 year manufacturer warranties. If you are weighing up a new boiler, we will give you a straight answer on whether you need one at all.
Need help now? Call DCI Boilers on 07888 862 603 or get a free quote.
Frequently asked questions
How long does a new boiler installation take?
A straightforward like-for-like swap is usually done in a day. Relocations, flue rework or conversions between boiler types can take two to three days. Your quote should tell you how long to expect before work starts.
Is a more expensive boiler worth it?
Often, yes, but for the warranty rather than the badge. A boiler with a 10 or 12 year manufacturer warranty spreads its cost over far more years of guaranteed cover. Just remember most long warranties require an annual service to stay valid.
Can I get a new boiler on finance or through a grant?
Some grant schemes exist for certain households and property types, but eligibility rules change and not everyone qualifies, so never assume you are covered without checking. Ask us and we will point you honestly at what may apply to you.
What size boiler do I need?
It depends on the number of radiators, bathrooms and the size of your home. Most homes fall between 24kW and 35kW, but the right answer comes from a survey, not a rule of thumb. Oversizing wastes money and undersizing leaves you cold.