Boiler installation – How much should it really cost?

Posted in Boilers | Planned Preventative Maintenance (PPM) | Plumbing | Property Maintenance
Published on May 22, 2019

How much should boiler installation really cost?

The cost of purchasing and installing a new boiler can vary enormously, even between boilers of the same type. Here, we take a look at what you should really expect to pay for your new boiler to be installed, and why. Boiler installation is a complex task and should only be undertaken by a qualified, Gas Safe Registered engineer.

How much is a new boiler itself?

Depending on the type, boilers can range from £500-600 for a small domestic boiler, to £2,000 for premium domestic models, all the way up to £6 or 7k for a large commercial unit. Combi or system boilers are, as a rule, cheaper than conventional heat-only boilers.

Why do boiler installation costs vary?

Installation costs depend to some extent on the boiler you’re getting, as well as the installation location. A straight replacement in the same spot, for example, will cost far less to install than a completely new, different boiler in a different location. This is because new pipework will need to be fitted, on top of any necessary modifications to the location itself.

So what can you expect to pay for boiler installation?

Here are some typical prices for a variety of boiler replacement scenarios. Costs include boiler, labour, parts and VAT – and we’ve included a power flush as standard.

Conventional (heat only) boiler

Regular boilers are heat-only. The boiler provides the heating and a cylinder provides hot water. The scenarios below show costs for replacing a regular boiler in its existing location, and for installing a new regular boiler in a new location.

The cost for moving the boiler will depend on whether it will be in the same room or moved to another room. Both of these prices assume that the cylinder and other equipment not directly related to the boiler remain in the same place.


  • Replacing a heat only boiler, same location: £2,350 (2 days)
  • Replacing a heat only boiler, new location: £2,750 (2.5 days)

Assumed mid-range boiler cost of £800.

Old boiler - Kiasu Workforce;

Combi boiler

Combination boilers provide both heating and hot water via the boiler, with no need for a cylinder. Usually, a combi boiler installation will consist of either replacing an existing combi boiler, or replacing a conventional boiler and hot water cylinder.

Replacing an existing combi boiler

Here, we show approximate costs for a new combi boiler in situ, and in a new location.

  • Replacing a combi boiler, same location: £2,350 (2 days)
  • Replacing a combi boiler, new location: £2,950 (2.5 days)
  • Replacing a regular boiler & hot water cylinder with combi boiler: £3,400 (3 days)

This kind of replacement might need extensive additional works to remove the cylinder and redirect pipes to the new boiler location.

  • Replacing a conventional boiler & tank with combi boiler: £3,250 (3 days)

Assumed mid-range boiler cost of £900.

System boiler

System boilers use an unvented tank to provide hot water, as well as providing heating. System boilers offer excellent performance and are good for buildings with multiple bathrooms in use.

Common scenarios involve replacing an old system boiler in the same location, replacing a conventional boiler & vented cylinder with a system boiler & unvented hot water tank, and replacing a combi with a system boiler/unvented hot water tank (common for property extensions).


  • Replacing a system boiler, retaining the unvented hot water tank: £2,300 (2 days)
  • Replacing a conventional boiler/hot water tank with system boiler/unvented hot water tank: £4,450 (3-4 days)
  • Replacing a combi boiler with system boiler/unvented hot water tank: £4,650 (3-4 days)

Assumed mid-range boiler cost of £850.

Back boiler

Back boilers are now no longer installed, so these costs are for replacing a back boiler with a newer model. A conventional boiler can be installed, retaining the hot water tank, or a combi boiler can be installed without the tank.

  • Replacing a back boiler with a new heat only boiler, retaining the hot water tank: £3,150 (3 days)
  • Replacing a back boiler and hot water tank with a new combi boiler: £3,450 (3 days)

Assumed mid-range boiler cost of £850.

What are the extra costs?

Costs include boiler, labour, parts and VAT. They are typical for a mid–range boiler, three-bed house and standard boiler installation set up. Most companies now include a power flush at no extra cost when fitting a new boiler. We assume this is included – as it is when we carry out boiler replacements.

Fittings, fixtures and pipework add onto the total cost, as do the materials and consumable tool parts required to complete works. Extra costs can be added if, for instance, the gas pipe needs to be re-run, a condensate pipe needs installing, the system needs sealing, TRV installation is required, or more extensive building works are required.

Boiler Plus

Any combi boiler replacement needs to be Boiler Plus compliant. Boiler Plus, which came into effect in April 2018, sets out revised energy efficiency and technical requirements for any new or replacement gas boilers being fitted in England.

The scheme stipulates that timing and temperature controls are required in new or replacement combi boilers An additional energy efficiency measure is required, such as weather compensation, load compensation, Flue Gas Heat Recovery, or smart heating controls. Each compliance method can be tailor-made for the customer’s requirements.

Summing up

The cost of each boiler installation depends on the individual building, the existing setup and the new boiler’s requirements. Additional factors such as construction costs and individual access requirements can also drive up costs.

Expect to pay upwards of £1,000 in any circumstance, plus the cost of the boiler itself, and block out 2 or 3 days for the installation. If you’re a low-income family, you might be eligible for a government boiler grant.

With that in mind, it’s important to ensure your boiler is living its best life. Hashtag blessed. Watch out for the telltale signs that your boiler is on its way out.

Most importantly, please make sure your boiler replacement is carried out by a qualified, Gas Safe registered engineer!

Article by Barney Scott, Kiasu Group

© 2019 Barney Scott, Kiasu Group