The Ultimate Guide to Boiler Installation Costs

By | 18th February 2017

76% of homeowners reported that final bills from tradesmen were more than the initial quote (research by Powered Now).

Dodgy tradesmen are costing us, £600 each – that gets under my skin.

And it gets worse.

1 in 6 homes have an unsafe Gas appliance. Between you and 5 friends, there is one family at risk and that’s just scary.

I’ve developed this boiler installation cost guide using research (I work at a plumbing merchants), as well as help from my brother and cousin (both Gas Safe engineers).

I’m going to show you how to think like a Gas Safe engineer. To make sure you get the best price but more importantly, to make sure your family are safe.

But, before we go any further, it’s always worth getting 2-3 quotes from Gas Safe boiler engineers. Listen to their advice regarding fitting magnetic system filters, and the type of boiler that is suitable for your property.

Here is what our boiler guide is going to allow you to do.

  • Get a fixed priced quotation, knowing there will be no hidden extras.
  • Typically save £800-£1,000 in comparison to British Gas quotes.
  • Find a Gas Safe engineer that is legally allowed to complete your installation.

What’s included in this guide:

  • What type of boiler do you have?
  • 16 common factors that increase boiler installation cost
  • Typical boiler replacement costs
  • How do these prices compare to British Gas?
  • Should I buy parts direct from a merchant to save money?
  • How to check your installer is Gas Safe registered.

What type of boiler do you have?

Before you can get an accurate quote, you’ll need to figure out which type of boiler you have. As an example, a cheap combi boiler is around £600, whereas if you can find an oil boiler for less than £1,000 (here’s an example). I’d like to know where from.

Combination boiler (Combi)

The most popular and efficient boiler on the market.

You will NOT have a hot water cylinder.

Heating and hot water are provided through the same boiler unit (i.e. there are no storage tanks).

Oil Boiler

It’s likely you’ll have an oil boiler if you are not connected to mains gas (or mains gas was not connected when the last boiler was installed).

System boiler

You WILL have a hot water storage tank (or cylinder). They are fitted in larger properties where a combination boiler would not be able to heat enough water on demand.

Regular boiler

If you have a hot water storage tank, a cold water storage tank (usually in a loft) and a boiler. It’s likely yours is regular (or “heat only”). These are usually fitted in larger properties (2-3+ bathrooms).

Not sure what boiler you have, or whether it’s really the right one for your property? Email us now and we’ll let you know.

16 common factors that increase boiler installation cost

Here’s the scenario.

You get an online estimate. After a home survey, the price spikes.

The work goes ahead, the engineer finds “more problems”, and adds to the final bill.

I feel your pain.

The table below this list highlights the estimated cost for each issue.

  • Mains water pressure – It’s uncommon, but some properties don’t have enough water pressure. They’ll have boiler problems, and think it’s the boiler, not the mains water pressure. Some common culprits for low water pressure include corrosion on supply pipes and faulty pumps (usually used in flats). Your property should have over 1 bar of pressure.

Quick test: Turn off all the taps in your property. Using one. Fill a 4.5L/9L container. If your pressure is reasonable, you should fill the container in 30/60 seconds. Your flow should be aiming for the 9 litres per minute mark.

  • Hot flush or power flush – As a minimum, when installing a new boiler, you’ll need a hot flush. It breaks down and removes the build up of sludge in the system. A hot flush is usually enough to get rid of this build up. A power flush is much more intense.

There are two big problems with power flushes (especially for old systems).

Firstly, they put an immense amount of pressure on soldered joints, and sometimes leaks occur.

Secondly, for the extra cost, it usually makes a lot more sense to add more energy efficient (and more aesthetically pleasing) radiators.

  • Premium boilers – Worcester Bosch is the perfect example. The like-for-like equivalent boiler from another brand (such as Ideal), is going to be £150-400 cheaper.
  • Type of boiler – Combination boilers are the cheapest. Systems are slightly more expensive, and oil boilers are the most expensive.
  • Scale inhibitor – “Hard water” contains particles that will see a build up of lime scale. To combat this, a scale inhibitor is fitted. This is not needed in all areas. You can see a list of hard water areas here.
  • Magnetic central heating filter – Check this is included in the quote. See this as the oil for your car. It protects your boiler. For Worcester Bosch boilers, a Worcester branded filter will actually add a years warranty.
  • Extended warranties – Worcester Bosch boilers come with a standard 5 year guarantee (this can be increased to 10 in some cases). Ideal boilers they offer boilers with a 2, 7 and 10 year guarantee.
  • When an installation is actually an upgrade – Base installation costs are usually derived from a straight swap (removal of old boiler, and installation of a new one in the same place). An upgrade (such as swapping a heat only for a combination boiler) or moving the boiler to a new location, will incur extra costs.
  • Ease of installation – Although Worcester are a leading brand, they are not particularly easy to install. They take longer. That means more labour and extra costs.
  • Use of existing controls – Boiler controls cost money. You’ll have a mechanical timer and a room thermostat. If you don’t have controls (or need new ones). It will cost. Basic controls can be under £100. But high-tech setups are available that cost up to £400 (i.e. turn your heating on from your phone when you leave work – check out Nest – made by Google).
  • Location of the gas main – The Gas Safe engineer will need to run copper pipe from the gas main, to your system. We find around 1/5 properties exceeds the threshold in terms of distance and difficulty.
  • Boiler in a new location – This is going to take time, and will cost in materials.
  • Gas run upgrade – Due to new Gas Safe regulations, many gas runs need to be re-piped.
  • Addition of a condensate pump – A condensate pump gets rid of waste water (which can be acidic and needs to go through the existing drainage system).
  • Excessive building works required – In general, an engineer will cover up an existing flue hole, and that’s about it. Any other works (removing and relaying floors, new brickwork etc) will incur an extra cost.
  • Type of flue – Most installation quotes will be inclusive of a standard horizontal flue. But, you may need a vertical flue (more expensive), a couple of extensions, and a flashing kit.

Summarising above, here is what you should expect to pay.

Factors that increase the price of a boiler installation

Likely extra cost in comparison to a standard installation

Upgrade mains water supply/pressure It’s a legal requirement that water suppliers supply us with at least 1 bar of pressure to the boundary of the property. If your pressure is low, speak to your supplier before doing anything else.
Hot flush or power flush £225-350
Premium boilers £150-400
Type of boiler £300-1,500
Scale inhibitor installation £55-85
Magnetic central heating filter £130-250
Extended warranties £100-200 for each upgrade in warranty (i.e. going from 2 to 7 years, or 7 to 10 years)
When an installation is actually an upgrade £500-1,250
Ease of installation £80-120
Boiler controls £100-400
Location of the gas main £50-100
Moving a boiler to a new location £250-400
Upgrading a gas run £80-100
Addition of a condensate pump £90-120
Excessive building works £100+
Type of flue package needed £30-200

It’s easy to see how one quote (even using the same boiler) can vary.

Should I buy parts direct from a merchant to save money?

I’m telling you right now. Don’t do it.

A good Gas engineer will charge you for:

  • Researching the best system for your property.
  • Time spent ordering parts.
  • Time spent collecting parts.
  • Risk of parts being fault (leading to time spent returning parts).

Rightly so.

You will not save money by ordering parts directly. Why?

Plumbing and heating merchants give preferential rates to their loyal customers. Online prices for boilers might be competitive, but the reduced cost of fittings a gas engineer will get usually outweighs the saving of buying a boiler online.

Trust me. I work at one.

But there are some bigger issues to consider.

#1 The parts are wrong

You misinterpret what the gas engineer lists for parts. He turns up at the job. And he has to stop work because of lack of, or incorrect fittings.

Guess who is paying for this? You.

If you’re on a fixed price (parts and labour) and the same thing happens guess who pays for it? The engineer.

#2 Parts are defective – need to be returned

This is my pet hate. Returning items. It’s never easy. But usually it’s a £15 lamp shade on Amazon, not a £700 boiler.

If you supply a boiler to your installer and it’s defective. Guess what happens?

You need to get it returned, and a replacement sent out. Good luck with that.

I can tell you right now that we install a lot of trust in the gas engineers that buy from us.

If they walk through the door saying a boiler is defective. They walk out with a new one, no questions asked – within 5 minutes. We deal with the returns procedure. And we still feel like we owe them.

Why? Because this just cost them. Big time.

They ripped out a boiler. Installed a new one. Had to remove it. Go and fetch a new one. And then re-fit.

But wait. You supplied the boiler? Guess what.

You WILL have to pay your engineer a refit charge. After all, they agreed to install one boiler with functional parts supplied. Not to install, remove, then install again.

Like I said. It’s not worth the hassle.

If you are looking for a new boiler installation, you can get quotes from up to 3 engineers here.

Installation Costs

The four most common types of boilers are:

  • Oil boilers
  • Combination boilers
  • System boilers
  • Back boilers

After consulting a few local Gas Safe engineers, and taking into account our own prices, we’ve come up with some estimates of labour costs.

The prices below give you a ball park as to what you’re installation or upgrade for your central heating system is going to cost.

Here is what we have based our figures on:

  • 30kw Ideal boiler with a 7 year warranty
  • Magnetic system filter
  • Basic controls and room thermostat
  • Hot flush

Cost Guide

Work required Boiler Type Cost
Replace boiler, using the existing location Regular £1,700
Combination £1,750
Replace boiler, moving to a new location Regular £1,950
Combination £2,000
Central heating system upgrade to a combination boiler (including removal of hot water tanks)


Regular £2,750
Back boiler £2,850
Upgrade to a system boiler (retaining hot water tanks) Back boiler £2,400
Upgrade to a combination boiler Back boiler £2,700

How do these prices compare to British Gas?

Many of the people we offer boiler quotes to have already had one, usually by British Gas.

Typically, a like-for-like quote (exactly the same fittings, controls and boiler) will be £700-1,000 cheaper than British Gas.


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