A combi boiler (combination boiler) is one of the most popular heating solutions for modern homes in the UK. By providing central heating and instant hot water from one compact unit, combi boilers offer space-saving design, efficiency, and great value.
Whether you’re replacing an old boiler, upgrading from a conventional system, or fitting heating in a new property, understanding combi boiler installation helps you choose the right setup. At RJG Heating & Plumbing Ltd, we specialise in boiler installation across Surrey and help homeowners upgrade to reliable, efficient heating systems.
What Is a Combi Boiler?
A combi boiler provides both heating and hot water from one unit. Unlike traditional systems, there’s no hot water cylinder or cold water storage tank. Water is heated on demand, so you get instant hot water whenever you turn on a tap or shower.
Cold water enters directly from the mains, passes through a heat exchanger inside the boiler, and is heated instantly. A separate circuit supplies hot water to your radiators for central heating. Heating and hot water can be controlled independently for better efficiency.
Benefits of Combi Boiler Installation
- Space-saving design – No cylinder or loft tank, freeing up valuable space.
- Instant hot water – No waiting for tanks to heat up.
- High efficiency – Modern combi boilers achieve 90%+ efficiency.
- Lower running costs – You only heat water when you need it.
- Mains-pressure hot water – Good shower and tap flow rates.
- Flexible installation – Fits in kitchens, utility rooms, or cupboards.
- Lower installation cost – Simpler than system or conventional boilers.
- Reduced maintenance – Fewer components than traditional systems.
- Better water quality – No open storage tanks.
- Ideal for smaller homes – Flats and homes with one or two bathrooms benefit most.
Limitations to Consider
Combi boilers aren’t perfect for every home:
- Multiple showers at once can reduce pressure and temperature.
- Low mains pressure can affect performance.
- Large homes with multiple bathrooms may be better suited to system boilers or unvented cylinders.
- High demand use may exceed what a combi can comfortably deliver.
We’ll advise if a combi boiler is suitable for your home or recommend a better alternative if needed.
Combi Boilers vs Other Systems
Combi vs System Boiler
System boilers handle multiple bathrooms better but need a hot water cylinder. Combi boilers save space and cost less to install.
Combi vs Conventional Boiler
Conventional systems need both a cylinder and loft tank. Combi boilers are more compact and modern.
Combi vs Unvented Cylinder
Unvented systems deliver better performance for multiple showers but cost more and need more space.
Combi vs Heat Pump
Heat pumps are more efficient but cost more upfront and need outdoor space. Combi boilers suit most properties and budgets.
Is a Combi Boiler Right for Your Home?
Combi boilers are ideal for:
- Flats and smaller homes
- 1–2 bathroom properties
- Homes with limited space
- Moderate hot water demand
- Properties without loft tanks
They may be less suitable for:
- Large homes with multiple bathrooms
- Heavy simultaneous hot water use
- Very low mains pressure
The Combi Boiler Installation Process
- Survey & Assessment
We inspect your current system, water pressure, pipework, flue, and space to confirm suitability and size. - Recommendation & Quote
We recommend the right boiler model and provide a fixed-price quote with no hidden costs. - Installation Day
We protect your home, remove the old boiler, and install the new unit with all connections, flue, and safety systems. - Commissioning & Testing
We fill the system, bleed radiators, test safety devices, and ensure correct operation. - Handover
We explain how to use your boiler, provide documentation, and answer any questions.
All work is carried out by Gas Safe registered engineers and fully compliant with building regulations.
Important Installation Considerations
- Mains water pressure must be adequate.
- Pipework condition may affect cost if upgrades are needed.
- Flue positioning must meet safety rules.
- Correct boiler size ensures efficiency and comfort.
- Gas and electrical supply must be suitable.
Combi Boiler Sizes (kW Output)
- 24–28 kW – Small homes, 1 bathroom
- 30–35 kW – Most average homes
- 36–40 kW – Larger homes or higher demand
We calculate the right size based on your property and usage.
Trusted Combi Boiler Brands
We install boilers from reliable manufacturers including:
- Worcester Bosch – Premium reliability and warranties
- Baxi – Strong mid-range performance
- Ideal – Great value and efficiency
- Navien – Modern, high-efficiency designs
We recommend the best option for your needs and budget — not the most expensive.
Cost of Combi Boiler Installation
Typical installed cost: £1,500–£2,500
Includes:
- Boiler unit
- Installation labour
- Standard flue work
- Commissioning and certification
Additional costs may apply for:
- New flue routes
- Pipework upgrades
- System flushing
- Converting from conventional systems
We provide fixed-price quotes with full transparency.
Maintaining Your Combi Boiler
- Annual servicing (often required for warranty)
- Monitor performance for noises or warning lights
- Bleed radiators if needed
- Use genuine parts for repairs
Regular maintenance improves reliability and lifespan.
Why Professional Installation Matters
- Gas safety and carbon monoxide protection
- Warranty protection
- Full building regulations compliance
- Optimised performance and efficiency
- Legal certification and documentation
Only Gas Safe registered engineers can legally install gas boilers.
Why Choose RJG Heating & Plumbing?
- Gas Safe registered engineers
- Specialists in combi boiler installations
- Fixed-price quotes with no surprises
- All major boiler brands supplied
- Full testing and clear handover
- Local Surrey-based service
- Ongoing servicing and support
- Fair, competitive pricing
Get Your Combi Boiler Installation Quote
Every home is different. The best way to get accurate advice and pricing is a professional survey.
Call 01932 885735 or request a free quote online.
We cover Addlestone, Shepperton, Chertsey, Esher, Walton-on-Thames, and surrounding Surrey areas.
Upgrade to a modern combi boiler and enjoy reliable heating, instant hot water, and improved efficiency.