New Boiler Cost UK: 2026 Prices and what affects them
In 2026, a new boiler installation in the UK typically costs between £2,000 and £4,000 supplied and fitted. Straightforward combi-for-combi swaps sit towards the lower end, while conversions, relocations, and back-boiler replacements can reach £5,500–£7,000 or more.
There's never a great time to find out your boiler's given up the ghost. Whether it's the middle of January or you've just noticed your energy bills creeping up month after month, replacing a boiler is one of those jobs that needs doing — and needs doing properly.
At RCB Plumbing, we carry out boiler installations across Sutton, Carshalton, Epsom, and the wider South London and Surrey area every week. One of the questions we get asked most often is: "how much is a new boiler going to cost me?" The honest answer is that it depends — but this guide will walk you through what to expect, what affects the price, and how to avoid any nasty surprises along the way.
The quick answer: average new boiler cost in the UK (2026)
Before we get into the detail, here's a useful distinction: the boiler unit price (the appliance itself) and the installed price (everything included) are very different numbers. Most online searches return boiler-only prices, which can make the final quote feel like a shock. A realistic planning figure for a fully installed boiler includes labour, flue work, controls, system cleaning, and disposal of the old unit.
Prices vary by property, flue and condensate routes, controls, system condition, and any additional work required.
According to Let's Heat (updated August 2026), the Energy Saving Trust currently uses around £3,700 as a typical installed cost for replacing an inefficient gas boiler with a new A-rated model and thermostatic radiator valves.
If you're in Surrey or South London and want a price based on your actual property rather than a national average, we're happy to help — request a callback here.
What affects the cost of a boiler replacement?
The boiler unit is only one piece of the puzzle. Here's what else moves the price up or down:
Boiler type
A straight combi-for-combi swap in the same location is generally the most straightforward — and most affordable — replacement. Converting from a regular or system boiler to a combi involves removing cylinders and tanks and rerouting pipework, which takes more time and materials.
Boiler size (kW) and hot water demand
Bigger isn't always better. A correctly sized boiler runs more efficiently, so it's worth getting this right. Output is determined by the number of radiators, bathrooms, and your home's heat loss — not just the square footage.
Brand and warranty length
Well-known brands like Worcester Bosch, Vaillant, Ideal, Baxi, and Glowworm (all of which we install) offer warranties ranging from around 5 to 12 years. Longer warranties often come with higher unit prices, but the long-term peace of mind can be well worth it.
Flue position and length
A flue through a nearby external wall is typically simple and inexpensive. Vertical flues, long flue runs, or awkward access all add time and cost.
Condensate drain route
This one trips people up, particularly in older properties. If the condensate pipe needs a long run or external routing, it can add to the job — and it needs to be done properly to avoid freezing in winter.
Controls and upgrades
Adding a smart thermostat or zoning controls is a great time to do it during an installation. We install smart heating controls as a standalone service too, but bundling it into a boiler replacement is often more cost-effective.
System condition
A new boiler won't fix a system full of sludge. If your heating system hasn't been flushed in years, a powerflush may be recommended before or during installation. Expect to add roughly £200–£400 for this.
Property type and access
Flats, Victorian terraces, and 1930s semis all throw up different challenges — awkward boiler positions, limited access, or outdated pipework. These factors can affect how long a job takes and therefore the overall cost.
Installation scenarios and realistic price bands
Rather than abstract price ranges, here are the scenarios we most commonly encounter:
Straight combi swap (same location): £2,000–£3,500. Typically a one-day job.
System boiler replacement (cylinder checks included): £2,200–£4,000, depending on whether the cylinder and controls need updating.
Converting from regular to combi: £3,500–£5,500+. This involves removing loft tanks and a cylinder, rerouting pipework, and more installation time.
Moving the boiler to a new location: £3,000–£5,000+. New gas pipe, heating connections, condensate route, and flue all need sorting.
Back boiler replacement: £4,000–£7,000+. These are some of the more involved jobs — a new boiler position needs to be found and the old appliance safely removed.
Upgrading controls and adding a magnetic filter/flush: Add £200–£600 depending on what's needed.
Hidden costs to watch for
The most common source of frustration isn't the boiler price — it's discovering that the cheapest quote didn't actually include everything. When comparing quotes, always check whether the following are included:
Removal and disposal of the old boiler
Magnetic filter installation
System inhibitor and cleaning
Heating controls (thermostat, programmer)
Building Regulations notification
Manufacturer warranty registration
Commissioning and testing
At RCB Plumbing, we'll always explain what's included upfront so you can compare quotes fairly — no awkward surprises halfway through the job.
How to get an accurate quote: our quick checklist
Before calling an installer, having this information handy will help you get a more accurate quote first time:
Current boiler type and location (combi, system, or regular?)
Number of bathrooms and bedrooms
Any known issues: cold radiators, low pressure, sludge
Preferred controls (basic timer, smart thermostat, or no change)
Mains water pressure (especially relevant for combi boilers)
Urgency — is it an emergency, or are you planning ahead?
Is it worth replacing your boiler in 2026?
Generally, yes — especially if your boiler is more than 10–12 years old, struggling to maintain pressure, or requiring frequent repairs. New A-rated condensing boilers operate at over 90% efficiency, compared to older models that can fall well below 80%. That difference shows up on your energy bills.
That said, not every fault means you need a full replacement. If your boiler is relatively young and a repair is sensible, we'll tell you honestly — that's just how we work. Annual servicing is also the single best way to extend a boiler's life and keep the manufacturer's warranty valid. You can find out more about our boiler servicing and boiler repair services if you're not quite at the replacement stage yet.
Choosing a boiler installer in Surrey and South London
Qualifications matter. Gas boiler work must be carried out by a Gas Safe registered engineer — always check this before hiring anyone. Beyond the legal requirements, look for:
Transparent, itemised quotes
Clear communication about what's included
Tidy workmanship and a proper handover
Realistic timelines (not "definitely done by lunchtime" promises)
Aftercare options like care plans or annual servicing
We're a family-run heating company based in Sutton with over 24 years of experience serving homes across South London and Surrey. We aim to offer same-day appointments where available and can be reached 24/7 for urgent issues. If you're looking for boiler installation in Surrey or South London, we'd love to hear from you.
Frequently asked questions
How much is a new boiler with installation in 2026?
For most UK homes, expect to pay between £2,000 and £4,000 for a straightforward replacement supplied and fitted. Complex conversions, relocations, and back-boiler replacements can cost £5,500–£7,000+. According to Let's Heat (2026), the Energy Saving Trust's typical benchmark is around £3,700 for an A-rated replacement.
What's the average price of a boiler unit only?
Boiler units alone typically range from £600 to £2,000 depending on the brand, model, and output. This figure doesn't include installation labour, flue, controls, or system work — so it's rarely the useful number when you're actually budgeting for a replacement.
Is a combi boiler cheaper to install than a system boiler?
A like-for-like combi replacement is usually one of the least expensive boiler jobs, often completable in a single day. System boiler replacements can be similarly priced if the cylinder and controls are in good shape, but they become more involved if additional components need replacing.
Do I need a powerflush when replacing a boiler?
Not always, but often advisable — especially in older systems or where there's evidence of sludge or corrosion. A powerflush helps protect the new boiler and improves efficiency. We'll assess the system during the survey and advise you honestly on whether it's necessary.
Can I keep my existing radiators when I replace the boiler?
In many cases, yes. Provided the radiators are in good condition and correctly sized for the new boiler's output, they can usually stay. We'll check for any cold spots or signs of corrosion during our survey.
How long does a boiler replacement take?
A standard combi-for-combi swap in the same location typically takes one day. System conversions or boiler relocations may take one to two days or more, depending on the complexity of the job.
Will a new boiler lower my energy bills?
It can, particularly if you're replacing an older, inefficient model. New A-rated boilers run at over 90% efficiency, which can make a meaningful difference. The actual saving depends on your insulation, controls, usage habits, and how inefficient your old boiler was.
What boiler size (kW) do I need?
It depends on your home's heat demand — number of radiators, bathrooms, and property size all factor in. We size boilers properly during our home survey rather than guessing, as an incorrectly sized boiler can reduce efficiency and cause problems over time.
Do you cover boiler installation in Surrey and Sutton?
Yes — boiler installation across Surrey and South London is our bread and butter. We cover Sutton, Carshalton, Epsom, and the surrounding areas. Get in touch via our contact page and we'll arrange a survey at a time that works for you.
How often should a boiler be serviced to keep the warranty valid?
Most manufacturers require an annual service to keep the warranty valid. Skipping a service can void your cover, so it's well worth scheduling one each year. Our boiler care plans include annual servicing as standard.
Ready to get a proper quote?
If your boiler's on its last legs — or you simply want to know what a replacement would actually cost for your home — we're here to help. At RCB Plumbing, we believe in clear, upfront pricing with no hidden extras, and work carried out properly from start to finish.
We cover boiler installation across Surrey and South London, including Sutton, Carshalton, and Epsom. Give us a call or drop us a message at [email protected], or book a free boiler survey online. We'll talk through your options honestly and give you a quote based on your actual property — not a generic national average.
