New Boiler Cost UK 2026: What You'll Really Pay

A new boiler cost in the UK in 2026 typically falls between £1,800 and £3,500 installed for a straightforward combi swap. System and heat-only boilers usually come in at £2,000 to £4,000 installed, while converting from a regular boiler to a combi can run £3,000 to £5,000 or more depending on the pipework involved.

Those are typical UK market ranges drawn from published installer price guides in 2026, not one fixed number, because two identical boilers can cost very different amounts to fit in two different houses. The boiler itself is often less than half the bill - the rest is labour, materials, flue work, system cleaning and controls. Below we break down what you should expect to pay for each boiler type and property size, what drives a quote up, and how to compare quotes so you don't overpay. We're CAF Heating, a family-run Gas Safe firm covering Surrey and South London since 1996, and everything below is what we tell customers on the phone every week.

Typical new boiler prices in 2026 by boiler type

The single biggest factor in your quote is which type of boiler you need and whether you're replacing like for like or changing system type. A like-for-like swap - combi to combi in the same spot - is the cheapest job. A conversion, where the engineer changes your system type or moves the boiler, costs more because it involves new pipework, a new flue position and often a day or two of extra labour. If you're not sure which type your home needs, our guide to combi vs system boilers walks through the decision in plain English.

These are installed prices - boiler, labour, flue, standard materials and VAT where the installer charges it. Treat anything at the very bottom of a range with caution: a £1,500 "fully installed" combi usually means a budget boiler, a short warranty and corners cut on system cleaning.

New boiler cost by property size

Bigger homes need higher output boilers, and higher output boilers cost more to buy. Output is measured in kilowatts (kW), and the right size depends on your radiator count, bathroom count and hot water demand - not just floor area. Oversizing wastes money twice: you pay more upfront and the boiler cycles inefficiently for years afterwards.

A proper installer will size the boiler from a heat loss assessment or at minimum a room-by-room walkaround, not from a postcode and a photo. That's one of the reasons we always survey in person before quoting - more on that below.

What drives a boiler installation quote up

When customers get three quotes and one is £800 higher than the others, the difference is almost never the boiler. It's the extras - some essential, some optional, some padding. These are the extras that legitimately add to the price.

Moving the boiler to a new location

Relocating a boiler - say from the kitchen to the loft or garage - typically adds £300 to £800 to the job. The engineer has to extend or reroute the gas supply, run new flow and return pipework, reposition the condensate drain and fit a flue in the new location. Loft installations also need boarding, lighting and a fixed ladder to comply with regulations, which adds more if they're not already there.

Flue changes and extensions

A standard horizontal flue through the wall behind the boiler is included in most quotes. Anything beyond that costs extra: a vertical flue through the roof typically adds £200 to £500, flue extensions add £75 to £150 per section, and a plume kit to redirect steam away from a neighbour's window adds £100 to £200. Flue positioning is regulated - there are minimum distances from windows, doors and boundaries - so this isn't something to trim from a quote.

System cleaning, filters and inhibitor

Fitting a new boiler onto a dirty system is the fastest way to wreck it. Sludge in old radiators circulates through the new heat exchanger and clogs it. A chemical flush and inhibitor is the minimum on any install, and a power flush - typically £300 to £500 extra - is worth it on older systems with cold spots. A magnetic system filter (£100 to £200 fitted) catches debris before it reaches the boiler, and most manufacturers now require one for their longest warranties.

Controls and thermostats

Boiler Plus regulations require time and temperature controls on new combi installations in England, so a basic programmable thermostat should be in every quote. Smart controls like Hive, Nest or Vaillant's own sensoCOMFORT add £150 to £300 but pay for themselves in tighter control of your heating. Weather compensation, which adjusts the boiler output to outdoor temperature, is often a cheap add-on that noticeably improves efficiency on Vaillant boilers.

Conversions and pipework upgrades

Converting from a heat-only system to a combi means removing the cold water tank, the feed and expansion tank and the hot water cylinder, capping off redundant pipework and often upgrading the gas supply pipe to feed a higher output boiler. That's a two to three day job rather than a one day swap, which is why conversions sit £1,000 or more above a like-for-like replacement. Upgrading an undersized gas run on its own typically adds £150 to £400.

Supply-only vs installed boiler prices

You'll see boilers advertised online at supply-only prices that look temptingly low: a mid-range 30kW combi might be £900 to £1,400 on its own. Installed prices are higher because they include the parts you can't see on a product listing - flue kit, filter, chemicals, fittings, controls - plus a day or more of skilled labour and the commissioning, registration and certification that make the installation legal and keep the warranty valid.

• ◆Gas boiler installation is not a DIY job. It is illegal for anyone who isn't Gas Safe registered to fit a gas boiler in the UK, and an uncertified install can invalidate your home insurance.
• ◆Manufacturer warranties require installation and commissioning by a Gas Safe engineer, and registration within a set window - usually 30 days. Buy supply-only and fit it badly, and the warranty is worthless.
• ◆Building Regulations require the installation to be notified to your local authority. A registered installer does this automatically and you receive a certificate - you'll need it when you sell the house.
• ◆The installed price includes making good: draining down, removing the old boiler, disposing of it, and leaving the system cleaned, inhibited, balanced and working.

Supply-only figures are useful for spotting whether an installer has marked the boiler itself up heavily, but they are not a price you can actually buy a working installation for.

Running costs: why a new boiler pays some of its way

Every gas boiler sold in the UK today is a condensing boiler running at over 90 per cent efficiency. Boilers from the early 2000s and before are often running at 70 to 80 per cent, which means for every pound you spend on gas, 20 to 30 pence goes up the flue. The Energy Saving Trust has good independent guidance on boiler efficiency and what replacing an old, inefficient model can save on a typical home's heating bill.

The savings are real but they're rarely a reason to replace a healthy boiler on their own. Where they matter is when your existing boiler is already costing you money in repairs, or it's over 12 to 15 years old and a major part fails. At that point the repair-vs-replace maths usually favours replacement: you stop pouring money into an appliance near the end of its life, you cut your gas use, and you get a long parts and labour warranty that makes your heating costs predictable for a decade.

If you want to squeeze the most from a new boiler, ask your installer to set the flow temperature correctly at commissioning and fit weather compensation where the boiler supports it. Small settings make a noticeable difference over a winter.

Boiler warranties in 2026: what 10 years requires

Warranty length is one of the biggest hidden differences between quotes. The same Vaillant boiler can come with a 5 year guarantee from one installer and 10 years from another, at a similar price. The difference is the installer's accreditation. Vaillant's extended 10 year parts and labour guarantee is only available when the boiler is fitted by an approved installer, registered within 30 days, installed with a boiler protection kit, and the system is flushed and inhibited to the British Standard. It also requires an annual service to stay valid.

We're a Vaillant Approved Installer, so our customers qualify for that 10 year cover as standard on eligible models - we explain exactly how the scheme works in our guide to what a Vaillant Approved Installer is. We also install Worcester Bosch and Ideal where they're the better fit for the house or the budget. Whatever brand you choose, a 10 year parts and labour warranty means your only planned boiler cost for a decade is the annual service.

• ◆Check the warranty is parts AND labour - parts-only cover leaves you paying an engineer's time on every claim.
• ◆Check who registers it. The installer should register the guarantee for you within the manufacturer's window; ask for confirmation.
• ◆Check the service requirement. Missing an annual service is the most common reason warranty claims get rejected.
• ◆Check the small print on the protection kit and system cleaning - if the installer skipped the filter or the flush, the long warranty may never have been valid.

How to compare boiler quotes properly

Three quotes for "a new boiler" are only comparable if they cover the same work. Before you compare the bottom-line numbers, line the quotes up against this checklist and make sure each one states, in writing:

• ◆The exact boiler make, model and output (kW) - not just "a 30kW combi".
• ◆The warranty length, whether it's parts and labour, and who registers it.
• ◆System cleaning: chemical flush or power flush, plus inhibitor.
• ◆A magnetic system filter, named, not "filter if required".
• ◆The controls included, and whether they meet Boiler Plus requirements.
• ◆Flue work, condensate drain and any pipework alterations.
• ◆Removal and disposal of the old boiler and any redundant tanks.
• ◆Building Regulations notification and guarantee registration.
• ◆A fixed total price, not an estimate that can grow on the day.
• ◆How long the job will take and who is actually doing the work.

On timing: a like-for-like swap should take a single day, and anything longer needs a reason - a conversion, a relocation, a full system upgrade. Our guide on how long a boiler installation takes sets out realistic timescales job by job, so you can sanity-check what you're told.

Red flags when getting boiler quotes

• ◆A price given without anyone seeing the property or asking detailed questions about it.
• ◆Pressure tactics: "this price is only valid today" is a sales technique, not a heating survey.
• ◆No Gas Safe registration number on the quote, the van or the website - you can verify any engineer on the Gas Safe Register before they start.
• ◆"Estimate" instead of "fixed quote" - an estimate can grow once the boiler is off the wall and you have no heating and no leverage.
• ◆No mention of flushing, inhibitor or a filter. The install may be cheap because the system protection is missing.
• ◆A warranty that sounds long but is parts-only, or depends on a paid service plan with the same company.
• ◆Cash-only pricing with no written paperwork. No paperwork means no Building Regulations certificate and no warranty registration.

Online instant quotes vs a fixed written quote

Online boiler companies will give you a price in 90 seconds from a postcode and a few multiple-choice questions. For a standard swap - modern combi, same position, straight flue, sound system - those prices can be fair, and the convenience is real. The problem is that a large share of homes in our patch aren't standard, and the questionnaire has no way of knowing that.

Victorian terraces with original pipework, flats with awkward flue runs near a neighbour's window, homes with undersized 15mm gas supplies, systems full of sludge, boilers boxed into kitchen cupboards that are 40mm too small for the modern equivalent - none of that shows up in a drop-down menu. When it surfaces on installation day, one of two things happens: the price goes up, or the corner gets cut. Either way, the instant quote you compared against was never the real number.

A proper survey catches all of it before you commit. The engineer measures the space, checks the gas run, looks at the flue options, assesses the state of the system and asks how you actually use your hot water. The quote that follows is fixed because there's nothing left to discover. That's the approach we take at CAF Heating: a free survey at your home, then a fixed written quote with the boiler model, warranty, flushing, filter and controls all itemised. The price we quote is the price you pay.

What a new boiler from CAF Heating looks like

We're Carlton Fuller and Sons - Carlton founded the firm in 1996, and his sons Simon and Stephen are Gas Safe engineers alongside him. We install Vaillant as our first choice, plus Worcester Bosch and Ideal, across Surrey and South London from our base in Horley. Most standard boiler swaps are completed in one day, we register your guarantee and Building Regulations notification for you, and as a Vaillant Approved Installer we can offer the 10 year parts and labour guarantee on eligible boilers. If you're weighing up which brand to go for first, start with our best boiler for 2026 guide, then have a look at our boiler installation service and pricing pages for how we work.

Expect £1,800 to £3,500 for a straightforward combi swap in 2026, more for system boilers, conversions and relocations, and be suspicious of any number produced without someone standing in your kitchen. A fixed written quote from a Gas Safe firm costs you nothing and removes every surprise from the job.

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