What Does a New Boiler Actually Cost?
If you've been told you need a new boiler, the first question is inevitably: "How much?" The answer depends on several factors — the type of boiler, the brand, the complexity of the installation, and whether additional work like pipework changes, a power flush, or system upgrades are needed.
London prices are typically 10–20% higher than the national average due to higher labour costs, congestion charges for engineers, and the complexity of working in older buildings. Here's an honest, transparent breakdown of what you can expect to pay in 2026.
Boiler Prices by Type
Combi Boiler Installation
The most common boiler type in London, especially for flats and smaller homes. A combi boiler heats water on demand — no cylinder or tanks required.
- Like-for-like replacement (same position, same type): £1,950–£3,200
- Converting from a regular/system boiler to combi: £2,500–£4,500 (includes removing cylinder/tanks and rerouting pipework)
System Boiler Installation
Best for larger homes with 2+ bathrooms. Includes a hot water cylinder but no loft tank.
- Like-for-like replacement: £2,500–£4,000
- Including new cylinder: £3,000–£5,000
Regular (Conventional) Boiler Installation
The traditional system with a cylinder and loft tanks. Usually fitted as a replacement in properties with existing conventional pipework.
- Like-for-like replacement: £2,200–£3,800
What's Included in the Price?
A standard boiler installation quote from a reputable installer should include:
- The boiler unit itself
- Removal and disposal of the old boiler
- Standard flue kit (horizontal flue through an external wall)
- System filter (magnetic filter to protect the new boiler)
- System inhibitor (chemical treatment to prevent corrosion)
- All labour — typically a full day's work for a straightforward like-for-like swap
- Gas Safe notification (legally required for any new gas installation)
- Manufacturer warranty registration
- Commissioning and testing
Factors That Affect the Price
1. Boiler Brand and Model
The boiler itself is the single biggest cost component. Here's how the major brands compare for a mid-range combi:
- Worcester Bosch Greenstar 4000: £800–£1,200 (supply price). The UK's best-selling brand with excellent build quality and up to 12-year warranties.
- Vaillant ecoTEC Plus: £750–£1,100. A close second in popularity, known for reliability and efficient condensing technology.
- Ideal Vogue Max: £700–£1,000. Great value with compact dimensions — ideal for tight London cupboards. Up to 12-year warranty.
- Baxi 800: £650–£950. Solid, reliable, and well-priced. Good for budget-conscious homeowners. Up to 10-year warranty.
We fit all four brands and can recommend the best option for your specific needs and budget.
2. Location Changes
Moving the boiler to a different location (e.g., from a kitchen to a utility cupboard, or from the loft to the ground floor) significantly increases costs due to the additional pipework, flue routing, and labour involved. Budget an extra £500–£1,500 depending on the distance and complexity.
3. Flue Routing
A standard horizontal flue through an external wall is included in most quotes. However, if the boiler is on an internal wall, you may need a vertical flue through the roof (£200–£400 extra) or an extended horizontal flue run (£150–£300 extra for each additional metre).
4. Power Flush
If your heating system has sludge or debris (common in systems over 5 years old that haven't been maintained), a power flush is strongly recommended before connecting a new boiler. Fitting a new boiler onto a dirty system is one of the most common causes of early boiler failure. A power flush adds £400–£600 to the total cost but protects your investment.
5. System Upgrades
Your installation may require additional work such as:
- New controls/thermostat: £150–£350
- TRV (thermostatic radiator valve) upgrades: £15–£25 per radiator
- Pipework modifications: £100–£500 depending on scope
- Gas pipe upgrade: If the existing gas supply pipe is undersized for the new boiler, it may need upgrading (£200–£400)
- Chemical flush (if power flush isn't needed): £100–£150
6. Access and Complexity
London properties often present installation challenges that add time and cost:
- Upper-floor flats with restricted access (scaffolding, long flue runs)
- Listed buildings or conservation areas with planning restrictions
- Shared flues in blocks of flats (requires specialist Type C or balanced flue systems)
- Tight cupboards or awkward boiler positions that require precise engineering
Average Total Costs in London (2026)
Based on our experience installing hundreds of boilers across London each year, here are realistic all-inclusive prices:
- Budget combi installation: £1,950–£2,500 (entry-level boiler, straightforward replacement)
- Mid-range combi installation: £2,500–£3,500 (premium brand, standard replacement with power flush and smart thermostat)
- Premium combi installation: £3,500–£4,500 (top-spec boiler, relocation, full system upgrade)
- System boiler installation: £3,000–£5,000 (including cylinder)
How to Finance Your New Boiler
We understand that a new boiler is a significant investment. That's why we offer several ways to spread the cost:
- 0% finance: Available on all installations over £1,000, subject to status. Spread the cost over 12–24 months with no interest.
- Low-rate finance: Longer terms (up to 60 months) available at competitive rates for those who prefer smaller monthly payments.
- Pay on completion: No deposit required — you pay the full amount when the installation is complete and you're happy.
How to Get the Best Price
- Get at least 3 quotes: Prices vary significantly between installers. Make sure each quote includes the same scope of work for a fair comparison.
- Check Gas Safe registration: Never use an unregistered installer, regardless of how cheap their quote is. It's illegal, dangerous, and will void your warranty and insurance.
- Beware of very cheap quotes: If a price seems too good to be true, check what's included. Some installers quote low and then add extras once they've started the work.
- Ask about warranty: The warranty length is directly related to the quality of installation. We register every installation with the manufacturer to ensure maximum warranty coverage.
- Consider a service plan: Pairing your new boiler with a service plan ensures annual servicing (required for the warranty) and covers repairs, protecting your investment from day one.
Get a Fixed-Price Quote
At Heat-Plex, we provide transparent, fixed-price quotes with no hidden fees. The price we quote is the price you pay — guaranteed. Our quote includes a home survey to assess your specific installation requirements, a recommendation for the best boiler type and model, and a fully itemised breakdown of all costs.
Request a free quote online or call us on 020 7622 0444. We serve every London borough, from Fulham and Chelsea to Lewisham and Greenwich.