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How much does a boiler cost?

If you’re on the hunt for a new boiler, there’s a good chance that you’re confused by all the options out there and are wondering how much it’s likely to cost. There are a lot of factors that contribute to the cost of a new boiler, but this handy guide will explain why the cost can vary and will help you to understand how much you can expect to pay.

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If you’ve decided it’s time for a new boiler; there’s a good chance you’re feeling daunted by all of the different makes and models, and are wondering how much it’s likely to cost.

There are lots of factors that contribute to the cost of a new boiler, but this handy guide explains why the cost of a new boiler can vary. And will help you to understand how much you can expect to pay.

You might like our related blog: Boiler FAQs.

To start with, you’ll need to consider why you’re looking for a new boiler, and what type of boiler you need…

Why are you looking for a new boiler?

There are many reasons why you might be looking for a new boiler. And ultimately, the cost of a boiler will depend on what your heating and hot water needs are; and what you’re hoping to achieve from your new heating system.

Although we only tend to think about our boilers when they’re on the blink, there are lots of benefits of replacing an operational boiler, so you might be planning ahead.

But whether you’re replacing a boiler because your old one has stopped working; or you’re looking to improve your energy efficiency; remember that a cheaper initial outlay could cost you more down the line in fuel bills.

Although some modern boilers can be pricey, they could potentially save you money in the long run, by improving the energy efficiency of your home.

What type of boiler do I need?

Diagram of the 3 types of boiler.The next question to help determine cost, is what type of boiler you need. And whether this is a different type of system from what you already have.

Naturally, it will cost more to overhaul a whole heating system, rather than replacing like for like.

There are three main types of boilers: heat-only or conventional boilers; combination or ‘combi’ boilers; and system boilers.


Heat-only boilers

Diagram of a heat-only boiler system.‘Conventional’ or ‘regular’ boilers are sometimes known as ‘heat-only’ because very simply; the boiler provides the heating and a cylinder provides hot water.

These boilers have both a hot water cylinder (usually in the airing cupboard) and a cold-water storage tank in the attic or loft.

Heat-only boilers need a large feed tank which is usually stored in an attic or loft. This tank receives cold water from the mains and feeds it down to your boiler.

Once the fuel has been ignited, the heat exchanger warms water which is then transported to the hot-water cylinder by a pump.

This stored hot-water is then sent to your taps and radiators when you need it.

The main advantage of this system is that they work well in large households with multiple bathrooms because they can supply large amounts of hot water to multiple outlets at the same time.

They can also be fitted with an additional electrical immersion heater to provide you with back-up hot water in case your boiler ever suffers a breakdown.

The price of installing a conventional system will vary depending on your current situation and needs, but as a rough guide, the three cost scenarios are:

  • Replacing a heat-only boiler with a new heat-only boiler will cost between £1800-3000.
  • Upgrading from a heat-only boiler to a combi boiler will cost between £2200-£3500.
  • Switching from a heat-only to a system boiler will cost between £1800-3000.

Combi Boilers

Diagram of a combi boilerCombis are the most popular boiler type in the UK. They get their name because they provide both your heating and hot water from one all-in-one (combined) unit, with no need for external cylinders or tanks.

Combis can heat water directly from the mains when you turn on a hot tap. They typically have two heat exchangers, one for your heating (radiators) and the other for your hot water supply.

The primary heat exchanger focuses on your radiators and carries hot water around your home. The secondary exchanger is for heating the water that comes out of your taps.

The main advantages of combi systems are that they are space saving, due to there only being one component part, and they never run out of hot water. 

The price of installing a combi boiler will vary depending on your current system and needs, but as a rough guide, there are two main cost scenarios here:

  • The new combi boiler is replacing an existing combi boiler – this will cost between £1800-3000.
  • Upgrading from a conventional boiler to a Combi boiler will cost between £2200-£3500.

System Boilers

Diagram of a system boilerSystem boilers feature aspects of both a conventional boiler and a combi.

Like a heat-only boiler, a system boiler needs a hot water storage cylinder to heat and store hot water for your taps.

But it doesn’t need a tank in the attic because, like a combi, it takes its water supply directly from the mains.

This cold water is then heated via a heat exchanger, which transfers energy from the gas jets to the water. Once heated, the water is pumped into a large hot water cylinder, where it is stored until required.

Since there is a large store of hot water always available, a steady supply can be maintained even if multiple taps or showers are in use at the same time.

Similarly, to heat-only boilers, a main advantage of system boilers is that they work well in large households as they can supply hot water simultaneously to multiple bathrooms as it’s stored in the hot water tank.

It is unlikely that someone would wish to swap their existing system boiler for a combi or heat-only boiler, so the main cost scenario for a system boiler would be:

  • Replacing a system boiler with a new system boiler will cost between £1800-3000.

You can read about the pros and cons of system boilers here.

What brand of boiler?

A confused woman next to a Vaillant boiler.Just like with anything you buy, be it a mobile phone, or a pair of trainers; the brand (or manufacturer) of boiler that you choose can make a difference to the price that you’ll pay.

We often get asked: ‘which brand is best?’ by people looking for a new boiler.

People will often seek out the big brands when it comes to buying mobile phones and other gadgets, and want to know whether this is a tactic they should use when getting a new boiler.

But just as there’s no ‘one-size-fits-all’ boiler for everybody, there’s no ‘right’ boiler brand either. Each brand (and individual model within the brand) has their own pros and cons, which need to be weighed up for your particular needs.

But it’s definitely a good idea to do a bit of research into what options are available, so that you can make an informed choice on what will be the hardest working appliance in your home for at least the next decade.

The Heating People are not tied to any manufacturer and can work with the brand of your choice. But we have our favourites!

We are:

  • Vaillant Advance Installers;
  • Worcester Bosch Accredited Installers;
  • ATAG Selected Partners;
  • Viessmann Trained Installers.

Generally our favourites for the three different types of boiler system are as follows:

  • Vaillant ecoTEC Exclusive 835 with Green iQ and the ATAG iC Economiser Plus for combi boilers – due to their in-built FGHRS.  
  • ATAG for system boilers due to the advanced control options available; high build quality; and relatively low cost.

To find out more about our top 5 combi boilers of 2022, check out our related blog here.

What size boiler do I need?

When people talk about how powerful your boiler needs to be they are referring to the kW (kilowatt) output, rather than the physical size of the appliance itself.

The higher the kW output of a boiler, the more it can cope with your heating and hot water demands.

You need to choose a boiler that can cope with the heating demands of your home.

But this isn’t as easy as it sounds. It’s vital that you don’t oversize or undersize your boiler.

If you choose a boiler that’s too big, you’ll be wasting energy and paying over the odds on your bills.

But if it’s too small, it might not be powerful enough to heat your home, or give you enough hot water.

Size with a heat loss calculation

Worcester Bosch Greenstar 8000 next to a ruler and a question mark.But don’t worry – The Heating People will find the perfect size boiler for your needs by conducting a whole house heat loss calculation. This is included as standard as part of your free quotation, and it is industry best practice under The Building Regulations.

Beware of any engineer that wants to size a boiler by counting your radiators – this is completely inaccurate!

A heat loss calculation only takes about ten minutes on site. We use heat engineer software, as this gives us an accurate enough calculation to be able to size a gas or oil boiler.

For more detailed calculations for renewable energy systems or if your house is borderline between two boiler sizes, we can complete a room-by-room cross calculation for a more accurate result.

Rough guide to boiler size

But since we get asked this a lot, here is a very rough guide on the kW boiler that will cater to your home.

  • 24 – 30 kW Combi

Suitable to provide heating and hot water to a home with one bathroom. If you have an en suite with an electric shower, this size of boiler will still be suitable.

  • 30-36 kW Combi

Suitable for homes with two bathrooms. 

  • For larger homes with more than two bathrooms, a storage combination boiler or stored hot water should be considered. Although larger combi boilers are available, they’re often not the best solution.

How much does it cost to install a new boiler?

The price of replacing a boiler costs less than you might think. It obviously depends on what you are changing from, and what you are changing to. But as a rough guide, at The Heating People:

  • Replacing an existing combi boiler with a new combi boiler will cost between £1800-3000.
  • Upgrading from a heat-only boiler to a combi boiler will cost between £2200-£3500.
  • Replacing a heat-only boiler with a new heat-only boiler will cost between £1800-3000.
  • Switching from a heat-only to a system boiler will cost between £1800-3000.
  • Swapping a system boiler with a new system boiler will cost between £1800-3000.

Contact The Heating People today to arrange your free quotation.

What’s involved in a new boiler installation?

Once you have decided you need a boiler replacement, you may be wondering what process you can expect from The Heating People.

Although all homes and heating systems are different, this is a rough guide to the work included in the cost of an installation with us:


When you get in touch, we’ll arrange a convenient time to carry out a survey of your home.

On this visit we will discuss your wants and needs from your new heating system, review your existing system, and discuss the options available to you.

We’ll also take some technical measurements such as water flow rate, and we’ll measure your home for an estimated heat loss calculation. This enables us to determine the correct boiler for your home.


After visiting your home, we’ll send you a fixed price quotation. This will have details of the boilers we recommend based on your survey, together with any accessories and options that you may wish to add to your quotation.


Once you’ve decided to go ahead with the work, we’ll take a small deposit and confirm your installation date.

Arrival of the engineer at your home

On installation day, your engineer will discuss the planned work with you. They’ll explain where they need access to, and for how long, so that you can plan your day.

Protecting your home

Rest assured that your engineer will take good care of your home, and will put down floor coverings in all work areas and transit routes, so that your carpets will be protected from any debris.

Draining your old system

Your engineer may need to switch off your water for a short period while they drain down your old system.

Test the gas for leaks

Your engineer will complete a let by and gas tightness test to ensure that your gas emergency control valve is working correctly, and that there are no leaks on your gas pipework.

Removal of the old boiler

Your engineer will remove the old boiler and any old redundant equipment.

Flush and clean

Before and after a power flush.Depending on what we have discussed during the quotation stage, we will use the flushing method agreed upon, to ensure that your heating system is clean for your new boiler.

This will help to preserve the guarantee on your new boiler; extend the life of your boiler; help to prevent future breakdowns; and improve the efficiency of your heating system.

Upgrade and change pipework if required

To fit your new boiler properly, your engineer may need to alter or upgrade pipework. The Heating People use only copper or professional press fit systems; we do not use DIY style push-fit systems.

Making good

Where your new boiler’s flue is in a new position, we will make good the existing flue hole, with bricks that are of a close match to your home.

Fitting the boiler

Your engineer will then install your new boiler, the boiler flue, and make all the pipework connections.


Your engineer will then fit controls and accessories as agreed, such as: temperature sensors; thermostats; timers; system filters; and filling loops.

Commissioning of the system

Your engineer will then fill; test; set to work; and commission your system; filling out all commissioning test results in your benchmark log book.

This will document all safety test results and confirm that the installation complies with safety regulations.


Your engineer will then complete a handover with you when all the work is complete. This ensures that you are as informed as possible on how to operate the boiler, how to use all the controls, and how to get the best efficiency from your system.

Register the boiler

Once The Heating People have installed your new boiler, we will register it with the manufacturers to activate its guarantee and we will notify your local building control via the Gas Safe Register.

How long does it take to install a new boiler?

How long a boiler replacement will take, will vary depending on what work is needed, if your boiler is moving location or if you have a like-for-like boiler. It usually takes between 1-3 days.

Final thoughts…

We hope that you’ve found this blog useful.

If you would like to talk to someone about the cost of replacing or upgrading your heating system, please contact one of our team at The Heating People, who will be happy to help you.

You might like our related blog: 6 Top tips for replacing your boiler.