Rising energy prices have prompted many UK homeowners to consider upgrading to more efficient heating systems, like combi boilers. People often ask, “How much does it cost to install a combi boiler?”That’s actually a good sign—showing they’re doing their homework on procedures and costs beforehand.
The cost of installing a combi boiler depends on multiple factors. To plan your budget accurately, you need to understand what influences these costs and stay informed about current prices. In this guide, we’ll break down everything you need to know about combi boiler installation costs. Let’s dive in.
What is a combi boiler and what does it do?
A combi boiler is shorthand for a combination boiler, a compact, all-in-one unit that supplies both central heating and hot water straight from the mains. Newer models often achieve top energy ratings like A and have efficiencies exceeding 90%.
How It Works
The core parts of a combi boiler include the heat exchanger, burner, expansion vessel, and controls. Whenever the thermostat signals for warmth or a hot water tap is opened, the boiler ignites the gas burner located inside the chamber. Cold water from the mains is then heated by the heat exchanger and sent out to the central heating system and taps as hot water.
Suitable For: small to medium homes, small flats, terraced houses, properties with a single bathroom, or households with average hot water demand.
How much does it cost to install a combi boiler in 2025?
The total cost to install a combi boiler usually ranges from £1,650 to £4,200, inclusive of supply and labour. The labour charges alone are typically between £1,000 and £2,000, excluding the boiler unit or any extra work. Prices can vary depending on factors like your location, the complexity of the installation, and the specific model chosen.
Additional costs might also be incurred if extra services are needed, such as relocating the boiler, updating existing pipework, or making structural modifications.
For a simple replacement of an existing combi boiler with a new one, costs tend to be lower because the work is less invasive—this is often called a “like-for-like” swap—and usually involves fewer complications.
Combi Boiler Installation: Complete Cost Breakdown
Installing a combi boiler generally involves the unit price plus labour costs. Additional costs may arise if any additional components are required. Let’s take a detailed look at the complete cost breakdown of a combi boiler:
✔ Installation Cost by Combi Boiler Type:
| Combi Boiler Type | Boiler Cost Range(Supply) | Installation Cost Range(Labour Cost) | Average Cost | |
| Gas Combi Boiler | £650-£3000 | £1000-£2000 | £3000 | |
| Electric Combi Boiler | 12kW Electric combi boiler without built-in Cylinder | £1200-£1800 | £1000-£2000 | £3000 |
| 12kW Electric combi boiler with built-in 140L Cylinder | £2600-£3800 | £1000-£2000 | £4200 | |
| 12kW wall-mounted Electric combi boiler with built-in 40L Cylinder | £2100-£2500 | £1000-£2000 | £3500 | |
| 12kW floor-standing Electric combi boiler with 120L built-in Cylinder | £2600-£3800 | £1000-£2000 | £4200 | |
| Oil Combi Boiler | £2500-£4000 | £1000-£2000 | £4000 | |
✔ Installation Cost By Installation Type:
| Installation Type | Average Cost (supply and install) |
| Combi-to-combi Straight Swap in the same location as the previous one | £2500-£4000 |
| Replacing a combi boiler with a new one, in a different location | £2650 |
| Replacing a system boiler with a combi boiler | £4000 |
| Replacing a conventional boiler with a combi boiler | £4000 |
| Replacing a back boiler with a combi boiler | £4000 |
✔ Additional costs:
| Cost Type | Average cost |
| Power flushing | £1000(including VAT) |
| Magnetic Filters | £60-£160(supply only) |
| Thermostat | £150(supply only) |
| Moving the Previous Boiler | £1000 |
Factors that affect the combi boiler installation cost
Multiple factors can influence the cost of installing a combi boiler. The common factors are:
Boiler Size and Output:
The more hot water and heating demand your house has, the higher the power output you’ll need. For a single bedroom with one bathroom, a 9-18kW combi boiler is sufficient. For 2 bedrooms with 2 bathrooms, a 24-27kW boiler is recommended. Larger output and bigger boilers generally lead to higher installation costs.
Fuel Type:
Combi boilers can run on gas, oil, LPG, electric, or hydrogen. Not all fuels cost the same—gas boilers are usually more cost-efficient than other fuel types.
Brand and Model Type:
Well-known brands tend to be more expensive. Additionally, different models within a brand vary in price, with premium models costing more.
Features and Efficiency Ratings:
A-rated models are highly efficient (above 90%) and often include advanced features like smart controls and longer warranties. These high-efficiency boilers tend to have higher upfront costs.
Complexity of the job:
Installation costs increase with complexity. For example, a straightforward replacement (combi-to-combi) is usually cheaper than replacing a different type of boiler with a combi. More complex jobs, such as adding new pipework or upgrading the system, also increase costs.
Boilers Accessibility:
If your existing boiler is located in a hard-to-reach place, it is difficult for the gas engineer to replace, convert, or relocate it. Plus, the job will take longer, which will eventually add to labour costs.
Geographic location:
The cost of installing a combi boiler heavily depends on where you live. In London and the South East, prices are generally higher compared to other UK regions.
Choice of Installer:
Opting for local Gas Safe-registered heating engineers usually results in a lower average rate than hiring national installers.
Additional Components and Upgrades:
If your home needs extra work, like installing a new gas pipe or other components, the overall price will increase. Any missing parts or upgrades will also extend installation time and raise costs.
Pro tips to save installation costs
Some homeowners might have a tight budget and are searching for cost-saving options. Here are some pro tips to save on installations:
- Check for government grants and schemes you’re eligible for to reduce costs.
- Always get and compare at least three quotes before proceeding.
- Investigate if zero-interest financing options are available for your project.
- Choose trusted local installers with a Gas Safety registered certificate, proper licensing, insurance, and verified credentials.
- Planning around festive periods and busy seasons can help you save both money and hassle.
Final Words
While you’ve already figured it out, many are still wondering, How much does it cost to install a combi boiler? Getting a good estimate is crucial. It’s a smart move to budget an additional 10-15% for unforeseen expenses. Investing in a high-quality, efficient combi boiler can save you a lot on energy bills in the long run.
Just remember—choose your installer carefully. Low prices can be tempting, but might hide inexperience or poor quality work. Always check current prices and compare what’s included in each quote.
FAQ About Combi Boiler Installation Cost in the UK
How much is a combi boiler for a 4 bedroom house?
A combi boiler for a 4-bedroom house typically costs between £980 and £2900 for the supply. Labour costs usually range between £1000 and £2000. Keep in mind, these prices can vary depending on your property’s specific situation and any additional work required.
How much should a new combi boiler cost to install?
The total installation cost usually falls between £3000 and £4200, including supply and labour. Extra jobs, like system upgrades, can push this higher.
Can I still replace my gas boiler after 2025?
Yes, the 2025 ban applies only to new builds. The government has pushed back the deadline for existing homes until 2035, so you can still replace your gas boiler legally.
At what age is a boiler considered old?
Most boilers are considered old after 10-15 years, especially if they require frequent repairs or show signs of inefficiency.
How do I know when my boiler needs replacing?
If your boiler is over 10-15 years old, or if you notice leaks, strange noises, yellow flames, higher energy bills, or uneven heating, it’s probably time for a replacement.
Is it worth replacing a 20 year old boiler?
Yes, it’s advisable. Older boilers tend to be less efficient, more costly to repair, and more likely to break down. Upgrading improves efficiency and reliability.
Can I get a government grant for a new boiler?
Yes, you might be eligible for a government grant for a new boiler. First, check your eligibility for the schemes and apply accordingly.
