Three boiler types, three different price brackets
Before any number means anything, it helps to know which type of boiler you're actually pricing up, because the three main types solve different problems and cost differently as a result.
A combi boiler heats water on demand straight from the mains — no tank, no cylinder, hot water whenever you turn the tap on. It's the most common choice for smaller households and properties without much space for a cylinder cupboard. A system boiler works with a hot water cylinder but doesn't need a separate tank in the loft, making it a common choice for houses with higher hot water demand — more bathrooms, more people. A regular boiler (sometimes called conventional or heat-only) needs both a cylinder and a loft tank, and tends to suit older properties that already have that setup and aren't looking to change the whole system.
As a general guide to typical UK price ranges for the unit and installation combined:
- Combi boiler: roughly £1,500 to £3,000
- System boiler: roughly £2,000 to £3,500
- Regular boiler: roughly £2,000 to £4,000, often more if an old cylinder or tank needs replacing at the same time
These are broad national ranges, not quotes — the final price depends heavily on the brand, output size, and how much work is needed beyond simply swapping the boiler itself. Our boiler installation page has more detail on what tends to move a quote up or down.
What actually changes the price
The biggest single factor isn't usually the boiler brand — it's whether the job is a straightforward swap or a system change. Replacing a combi with another combi in the same spot, on the same pipework, is about as simple as boiler installation gets. Switching from a regular boiler to a combi, or moving the boiler to a different room, involves rerouting pipework, possibly removing a redundant cylinder and tank, and generally adds a day and a meaningful chunk of cost.
Other things that move the number:
- Flue length and route — a straight run through an external wall is simple; snaking a flue through multiple rooms costs more
- Boiler output size — bigger houses need higher kW output, which costs more
- Access — older rural properties, particularly ones with tight lofts or awkward airing cupboards, can add time
- Removing an old system — taking out an old cylinder, tank, or pipework isn't free labour
If you're on oil rather than mains gas, the installation itself follows a similar pattern but needs an OFTEC-registered installer rather than a Gas Safe one — worth checking on our oil boiler services page if that's your situation.
What install day actually involves
A straightforward like-for-like combi swap typically takes one day. A system change — different boiler type, different location, removing old tanks — commonly runs to two or three days. Neither of those is unusual or a sign something's gone wrong; it's just the difference between swapping a part and reconfiguring a system.
On the day, expect the installer to isolate the gas and water, remove the old boiler, fit the new one, connect the flue, pressure test the system, and commission the boiler — meaning they set it up correctly for your specific home rather than leaving it on factory defaults. A good installer registers the boiler with the manufacturer for you as part of the job, since a lot of extended warranties depend on registration happening within a set window after installation.
Warranties: read what you're actually getting
Boiler warranties vary a lot by manufacturer and by whether an installer is accredited to offer an extended term. Standard manufacturer warranties on a new boiler commonly start around 2 to 5 years, but installers accredited by certain manufacturers can often register you for considerably longer — sometimes up to 10 or 12 years — at no extra cost, simply because the installer's accreditation qualifies the customer for the manufacturer's extended scheme.
This is worth asking about directly before you agree to a quote: "What warranty length do I get with your installation, and is that because of your accreditation?" If two quotes are similar in price but one comes with double the warranty, that's not a marginal difference — it's years of potential free parts and labour if something goes wrong.
Keep the boiler serviced annually regardless of warranty length — nearly every manufacturer warranty is conditional on annual servicing, and a missed year can void it even if the boiler's only three years old. Our boiler servicing page covers what that annual check should include.
Choosing an installer, not just a price
The cheapest quote isn't automatically the wrong choice, but it's worth being cautious of a number that sits well below everyone else's without an obvious reason. Ask what's actually included — is the old boiler removal and disposal in the price, or an extra? Is a magnetic filter included, since it's cheap at install time and expensive to add later? Does the quote include a benchmark commissioning checklist, which some warranty claims require as proof the boiler was installed correctly?
Any installer working on gas boilers must be Gas Safe registered — check the ID card and, if you want to be thorough, verify the licence number on the Gas Safe Register site before signing anything. Our Gas Safe registration guide explains exactly what to check and why it matters legally, not just as good practice.
If you're not on mains gas
Everything above the pricing brackets applies broadly whether you're gas or oil, but if you're on an off-grid property without a gas main, it's worth at least getting a heat pump quote alongside a boiler quote, particularly if your existing system is old and due for full replacement anyway. It won't suit every property without further work, but for the right rural home it can be a genuinely better long-term option than another oil boiler. Our heat pump installation page explains what a suitability survey looks for.