How much does it cost to supply and install a combination boiler in London?

how much boiler cost

Are you trying to find out cost of new boiler? In this article I will give you a fully comprehensive answer as to how much new boiler installation should cost.

To answer this question we need to take a number of things into consideration. These are the most important factors that affect the cost of installation:

  1. Type of existing system – Boiler installations tend to fall into two categories: ‘direct swap’ and ‘change of systems. Direct swap (from existing combination boiler to new combination boiler) is usually the cheapest and can be completed relatively quickly. Change of systems means converting a vented system into a sealed system. This requires more work, which is why it is more expensive than a direct swap. How do you know what kind of system you have? If you have cold water storage tanks and hot water cylinder then most likely you have a unvented system which will be much more expensive than direct swap when installing your new combination boiler.
  2. Location of new boiler – For both direct swap and change of systems, it is usually cheaper to keep your new boiler where the old one was, rather than move it elsewhere.
  3. Gas supply upgrade – Some installations will require an upgrade of your gas pipework going from the meter to the boiler. It is more likely that an upgrade is required when changing systems. On direct swaps it will be only required if the new boiler is more powerful than the existing one, or if the pipework going to the existing boiler is undersized. Since combination boilers are heating water on demand, they require bigger gas input and bigger pipework compared with conventional or system boilers found on unvented or vented installations with hot water storage.
  4. kW rating of the boiler – Generally boilers with a bigger kW rating will cost more. Physical size is the same with most manufacturers. Your boiler size won’t be based on the number of radiators but on the required hot water flow. The smallest and cheapest combination boilers start at around 24kW and should give around 8 litres a minute flow of hot water. The biggest boilers will be 40kW with around 16 litres per minute.
  5. Condensate drainage – New condensing combination boilers require connection to drainage to drain away condensate. If, due to location, it is not possible to connect condensate drainage a condensate pump installation is required to pump condensate away. This makes the installation more expensive.
  6. Flue runs – Depending on the location of boiler installation longer flue runs may be required with flue boxing with access for inspection. This is why it is usually best to locate the boiler on external walls. Longer flue runs will make installation more expensive.
  7. Size of existing central heating system – This is important for two reasons. As power flushing to an existing installation is required on all new installations, it will be cheaper to flush smaller systems than bigger ones. Also, bigger systems may require additional external expansion vessels, adding to the cost.
  8. Boiler manufacturers and warranty options – There are a number of boiler suppliers offering products in different price brackets and with warranties ranging from one to 10 years. More reputable brands will offer longer warranties but will cost more to supply.
  9. Additional costs– Thermostatic radiator valves, new thermostats and controls, in line water softeners and magnetic filters all add to the cost of installation.
cost of new boiler installation

Let’s have a look at the figures:

  1. Type of system. Direct swap installation (labour and installation materials only) will cost between £400 – £800. System swap labour and installation materials should cost around £700 – £1500. As mentioned, it is cheaper to keep the new boiler in the same place as the old one.
  2. Location of the boiler. As a general rule add between £300 – £700 for moving the boiler.
  3. Gas supply upgrade – Depending on the distance from the gas meter and complication of the installation this should cost between £200 – £500.
  4. Size of the boiler. The cheapest 24kW boilers on the market cost around £400 to supply while the biggest ones 40kW from reputable suppliers can cost up to £1600 to supply.
  5. If condensate needs to be pumped a supply and installation of a suitable pump may cost between £180 – £300
  6. If longer flue runs are required I would suggest an allowance of £100 per meter to cover supply and installation of flue, flue boxing and access panels.
  7. Power flushing – small systems (up to 10 radiators) will cost around £200 to be flushed during the installation with £15-£30 extra per every additional radiator. If additional expansion vessel is required (usually on systems above 10-15 radiators) those cost about £80 to supply and install.
  8. Depending on manufacturer there may be an option of extended warranty (5, 7 or even 10 years) at an additional cost of between £150-£300 on appliance price. It is worth remembering when paying extra for an extended warrantythat boiler manufacturers require boilers to be serviced annually. Not servicing your appliance will invalidate your warranty. Cost of service will vary with region and servicing company but it should be in the area of £60-£100.
  9. Other costs to keep in mind:
  • Water softener or scale reducer – required for hard water areas. The cheapest in line ones will cost £40-£60 going well over £1,000 for proper water softening appliances
  • Thermostats and programmers – basic room stat will cost around £20 with around £200-£300 for WiFi controlled and programmable digital versions
  • Magnetic Filters – These are becoming more and more popular as they are believed to protect appliances and extend the life of components such as pumps and heat exchangers. They are optional and are regarded as good practice. Cost of supply and installation is around £80 – £150 depending on make and model. From my experience it is best to go for reputable manufacturers and avoid cheaper copies.

Here are some working examples of the fully inclusive cost of a new combination boiler installation based on the options describe. Feel free to ask questions or leave comments.

Example 1 – Direct swap, same location installation on small system on external wall with budget 24kW boiler. No magnetic filter or in line scale reducer required. Keep existing room thermostat, radiators already fitted with thermostatic valves.

  • Labour and installation materials – £400.00
  • Power flush – £190.00
  • 24kW budget boiler and flue – £560.00

Total of £1,150 + Vat

Example 2 – Direct swap, same location installation on large system, installation on external wall with budget 28kW boiler. Supply and install: in line water scale reducer, magnetic filter and no.12 thermostatic radiator valves.

  • Labour and installation materials – £420.00
  • Power flush – £250.00
  • 28kW budget boiler, flue and clock – £650.00
  • Scale reducer and magnetic filter – £200.00
  • 12 thermostatic radiator valves – £240.00

Total of £1,760 + Vat

Example 3 – Direct swap, same location, minor alteration to pipe work required, medium size system, gas upgrade not required, installation on external wall, good quality 24kW combination boiler with 7 years warranty. Supply and fit in line water scale reducer, magnetic filter and new programmable room thermostat

  • Labour and installation materials – £480.00
  • Power flush – £250.00
  • 24kW boiler with 7 years warranty and standard flue – £800.00
  • Supply and fit: scale reducer, magnetic filter, thermostat – £250

Total of £1,780.00 + Vat

Example 4 – Change of systems, different location for new boiler, gas upgrade required, installation on internal wall with 5 meter flue run. Supply and install: Nest controls, in line water softener and Magna Clean magnetic filter. New 40kW combination boiler with 10 years warranty. Large system with additional expansion vessel required.

  • Labour and installation materials – £750.00
  • Power flush – £350.00
  • 35kW boiler and flue with 10 years warranty – £1190.00
  • Nest controls, scale reducer and magnetic filter – £450.00
  • Additional expansion vessel – £80.00
  • Gas supply upgrade on long run – £400.00
  • 5 meter flue run with boxing and access panels – £425.00
  • 15 new thermostatic valves – £280.00

Total of £3,925.00 + Vat

If you are looking for a new installation in London please go to online booking to book a free no obligation quote.