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New boiler installation and replacement costs 2024

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Installing a new boiler will cost you around £1,900 – this covers the unit and installation price, which can account for 37 per cent of the total price. A modern boiler will improve your home’s energy efficiency rating and could save you up to £840 annually on your energy bills. The recent cost-of-living crisis has hiked gas prices up to 10.3p per kWh and electricity up to an eye-watering 34p per kWh. 

With that being said, many homeowners with older boilers can actually reduce energy bills by replacing them. Modern A-rated combi boilers reduce energy loss and carbon emissions, and will generally heat homes more efficiently. Older boilers with lower energy efficiency ratings have an adverse effect on energy bills. Old boilers that are G-rated run at just 70 per cent efficiency (30 per cent heat loss) compared to A-rated boilers, which run at 90 per cent or higher, ensuring your home isn’t wasting energy that can’t be utilised.

How much does a new boiler cost?

A new boiler can be a costly investment, but one that also helps to save money on your energy bills in the long run. There are a lot of contributing factors to the cost of a replacement boiler, with the most obvious being which boiler brand homeowners choose. In addition, boilers come with different capacity sizes and water flow rates, all of which affect the cost.

Typical house size Central heating output Average boiler price Average installation cost Average boiler price including installation
Three bedrooms 28kW £1,200 £700 £1,900

What are the benefits of replacing your boiler?

Purchasing a new boiler has plenty of benefits, including saving money on your energy bills, making it a worthy investment.

  • Increase energy efficiency rating in your home – combi boilers are rated for their efficiency, with A being the most efficient and G the least. A more efficient boiler will save you more on your energy bills 
  • Save up to £840 annually on your energy bills
  • Increase the value of your home by up to £9,000
  • Quieter system – boilers awarded the Quiet Mark have been technically assessed and certified 
  • Reduce carbon emissions – replacing an old G-rated boiler with a new A-rated model and a full set of heating controls could save an average of 1,200kg of carbon dioxide every year
  • A warmer, more comfortable temperature for your home

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How much will a new boiler save you on your energy bills?

Reduced energy bills with a new combi boiler. A person's hand writes the indicated reading from a gas meter in a notebook.
An energy efficient new boiler can help you save hundreds on your heating bills (Adobe)

Installing a new combi boiler has the potential to cut your energy bills by up to £840 per year. Contributing factors like your house size, location, energy consumption and energy rating will determine the exact savings you could benefit from. 

Based on October’s energy price cap, this is how much you could shave off your energy bills per year by replacing your old boiler with an A-rated model, according to Energy Saving Trust.

Old boiler energy efficiency rating
Property type ↓ D (78-82%) E (74-78%) F (70-74%) G (<70%)
Bungalow £250 £275 £310 £445
Flat £125 £140 £160 £230
Mid-terrace house £235 £260 £290 £420
Semi-detached house £305 £335 £380 £540
Detached house £375 £460 £590 £840

Boiler energy efficiency explained

No matter which type of boiler you choose, it will come with an energy efficiency rating. Energy efficiency ratings are a measure of how efficient an appliance is overall. It takes into account how much energy it uses and compares it to other similar appliances.

A boiler’s energy efficiency rating is determined by calculating the percentage of the total energy used to provide useful heating. If a boiler has a 90 per cent energy efficiency rating, that means 90 per cent of the energy is converted into usable heat and 10 per cent is lost in the process. 

Boilers have energy efficiency ratings of A-G, with modern A-rated boilers being the most energy efficient. 

  • A – 90% and above
  • B – 86% to 90%
  • C – 82% to 86%
  • D – 78% to 82%
  • E – 74% to 78%
  • F – 70% to 74%
  • G – below 70%

Modern A-rated boilers are the most energy-efficient, and this has a positive impact on energy bills. You will end up paying higher energy bills  with older G-rated boilers that are just 70 per cent energy efficient.

When should you replace your boiler?

Rusty pipe on a gas boiler close-up. A sign that you need to replace your boiler.
Leaking or rusty pipes are a sign that it is time to replace your boiler (Adobe)

Boilers typically have an average lifespan of between 10 to 15 years but can run for much longer than this. One obvious indicator that it might be time to replace your boiler is its age. A boiler’s energy efficiency decreases significantly when it’s over 10 years old. 

If your boiler is old, it may well present some undesired signs that it is time to replace it. 

What to look for:

  • Frequent breakdowns: If your boiler has repeatedly broken down recently, this is a sign that it needs replacing. On top of your yearly service, if you find yourself needing to call out an engineer more than once per year, chances are you need a new boiler.
  • High energy bills: Although energy bills have increased generally, if you notice your costs increasing unexplainably, this might be a sign that your boiler is not efficient. New A-rated boilers operate at 90 per cent efficiency compared to G-rated boilers, which run at 70 per cent. 
  • Noisy boiler: While some boiler and radiator sounds are expected, changes in the type or volume of noise may indicate that your boiler needs replacing. Pay careful attention to any type of umming, vibrating or banging sounds. 
  • Odd smells: Detecting any unusual odours from your boiler could be a sign of an emergency and you should contact a Gas Safe engineer immediately. Smelling a sulphurous, eggy odour might be a sign of a gas leak; if this is the case you might need to replace your boiler. 
  • Yellow flame: A change to your boiler’s flame or pilot light might be cause for concern if it has changed from its usual bright blue to a yellow or orange colour. A Gas Safe engineer can assess the damage to determine if your boiler needs to be replaced. 
  • Water leak: Boilers should never leak water. If you spot a water leak, turn off your boiler and wait for it to be assessed by a Gas Safe engineer. Whether you need a new boiler will depend on the internal damage.

How to tell if it’s time to replace a boiler – how long does a boiler typically last, and what should I look out for? –
David Hilton, Energy and Renewables Expert

david hilton

In the boiler industry, it is accepted that a new condensing-type boiler will last an average of around seven years. Of course, your boiler might last 15 years, but then there are some that will not last the full seven years. Many factors influence the lifespan of a boiler, such as servicing, water quality (hard water, acid water, alkaline water), proximity to a marine environment and others. When a condensing boiler is operating in an optimised way, it will be producing a lot of condensation on the heat exchanger. Condensation is slightly corrosive, and as such, the irony here is that the more efficient the boiler is, the shorter the life expectancy. Some brands can cope with this corrosion better than others, so it’s best to invest in quality.

Hard water is the enemy of boilers, and this is especially true with combi boilers. You can protect the central heating closed loop system with additives, but with an open (instant heat) heat exchanger, you would need to treat the water at source. The hard water leaves deposits that build up on (and in) the heat exchanger, pipework and fittings and cause problems. The heat exchanger can become blocked or coated and the water volume changes so that the water actually boils in the heat exchanger and makes a banging noise, which stresses the system. Valves can become stuck and, therefore, when you call for central heating, the valve cannot open and then often damages the electrical board in the boiler. When either of these things happen, they can be repaired but it is worth checking the rest of the boiler, as there may be other things that are also damaged, and it then can potentially make much more sense to replace the whole unit.

What to consider when buying a new boiler

House size

One of the most important things to consider when buying a replacement boiler is the unit’s central heating output. The higher the output required, the more costly the boiler will likely be. 

The size of your household determines which type of boiler is needed. As a general rule of thumb, homes require one radiator for every 5 cubic metres that need to be heated. The average UK house has 10 radiators, and it’s recommended that homes of this size install a boiler with a 28kW to 34kW central heating output range.   

Based on the size of the boiler required for each house size, this is the average price you can expect to pay for a new boiler. The average cost for a boiler installation is £400 to £500 for one day’s work, £700 to £1,200 for two days, and £1,000 to £2,000 for three days.

House size Flat Bungalow Terraced house Semi-detached house Detached house
Boiler average price £1,039.98 £1,179.99 £1,292.99 £1,399.99 £1,722.99
Average cost with one-day installation £1,439.98 – £1,539.98 £1,579.99 – £1,679.99 £1,692.99 – £1,792.99 £1,799.99 – £1,899.99 £2,122.99 – £2,222.99
Average cost with two-day installation £1,739.98 – £2,239.98 £1,879.99 – £2,379.99 £1,992.99 – £2,492.99 £2,099 – £2,599.99 £2,422.99 – £2,922.99
Average cost with three-day installation £2,039.98 – £3,039.98 £2,179.99 – £3,179.99 £2,292.99 – £3,292.99 £2,399.99 – £3,399.99 £2,722.99 – £3,722.99

Number of bathrooms

As well as heating homes, boilers also have much to do with heating water for showers and taps. The water flow rate is measured in terms of your gallons per minute (GPM) – it measures how many gallons of water could flow out of your shower or taps every minute; the higher the GPM, the higher your water pressure. 

Like with central heating output, boilers have what’s called a water flow rate. Homes with one bathroom should have their hot water demands met by boilers that have a water flow rate of between six and 12l per minute. Homes with more than one bathroom should consider a unit with a water flow rate of higher than 12l – the higher the better.   

Boiler brand

Like with any sizable purchase, it’s advisable to not only understand the product, but also to know how trustworthy a particular brand is. There are plenty of boiler brands to choose from, and most of them are good, but it’s worth taking the time to read customer reviews on sites like Trustpilot. Our researchers have reviewed combi boilers from all of the major brands to find the best options for various households.  


Boilers should last between 10 and 15 years, and are something we rely on to heat our homes and supply hot water. Like with any type of technology, a boiler can sometimes need repairs or replacement well before its lifespan is spent. All replacement boilers come with warranties, and different manufacturers and models carry different lengths, all of which you’ll want to carefully consider. 

Energy efficiency

Although most new boilers are A-rated, it is worth checking that your chosen replacement is too. Replacing your boiler is something that you’ll hopefully only do once every 10 years, which is why ensuring it is A-rated is so important. Boilers which are rated lower than this have a lower efficiency rate, resulting in higher energy bills.   

Smart controls

With the energy crisis in full swing, keeping energy bills low is a top priority for many homeowners. A boiler that is compatible with smart controls gives homeowners full control of their central heating. It’s a way of monitoring heat consumption as well as setting, adjusting and turning off heating, even if you’re away from home, via your smartphone.

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What type of boiler is right for you?

Combi, system and regular boiler types for home water heating outline diagram.
There are different types of boilers that suit different types of houses (Adobe)

There are several different types of boiler to choose from, and determining which one is right for your home has much to do with your house size and the number of bathrooms. 

Combi boilers

A combi boiler provides both central heating and hot water from the same unit, so it is the most compact option. Combi boilers do not require a hot water tank, which makes them ideal for homes lacking in space. 

Best for:

  • Smaller homes
  • Homes with one bathroom
  • 10 radiators or less
  • No loft or space to store a hot water tank
Pros Cons
Space saving Don’t work well in areas with poor mains water pressure
Instant heating – hot water when you need it without waiting for it to heat up in a tank W pressure drops considerably when more than one shower is being used
Energy efficient Not compatible with power showers
Easy installation with just one unit to fit Combi boilers have moving parts, which means there is more potential for things to go wrong
Easily serviced due to their popularity – most engineers are trained to work on combi boilers Not compatible with solar water heating systems

Electric combi boiler

Electric combi boilers work exactly the same as gas combi boilers, except they run on electricity rather than gas. While their running costs are higher – which is a major factor in their lower energy efficiency ratings – electric boilers can be considered more environmentally friendly, particularly if you power your home with solar panels or get your electricity from a provider that uses renewable energy sources such as wind and solar farms.

Best for:

  • Smaller homes
  • Homes with one bathroom
  • 10 radiators or less
Pros Cons
Electric combi boilers can be more environmentally friendly than those powered by fossil fuel More expensive to run
No risk of carbon monoxide leaks or poisoning Most electric boilers aren’t powerful enough for larger homes
No chimney or flue is required More expensive to purchase than a gas boiler
Tend to be quieter than gas boilers A power cut may impact access to both heating and hot water

Is an electric combi boiler greener than a gas combi boiler? –
David Hilton, Energy and Renewables Expert

david hilton

An electric combi boiler can potentially run on green electricity, whereas gas is always going to have a carbon footprint. However, the main criteria for me is the flow rate. To heat water instantly takes a fixed amount of heat per litre. Gas can practically deliver more heat energy than electricity. A 24kW gas boiler will heat 11l per minute by 35C, whereas a 35kW boiler will heat 14.4l by 35C and a 42kW boiler will heat 17l by 35C. An electric boiler is limited to around 8kW on a single-phase electric supply (that is what most houses have), so you get between three and four litres per minute.

Delivering less heat may indeed also be seen as a green solution, as you are using less water and also therefore less energy, but make sure you are happy that the solution meets your expectations.

Conventional boilers

Also known as heat-only boilers or regular boilers, a conventional boiler is powered by gas and heats up radiators directly. To heat hot water, conventional boilers are connected to a separate tank or cylinder, which heats up and stores hot water. With a conventional boiler, a pump transports hot water to radiators or to taps when switched on.

Best for:

  • Larger homes
  • Homes with more than one bathroom
  • Low mains pressure
  • An older house
Pros Cons
Good for homes with a high water demand -– hot water can run to several taps at once A finite amount of hot water – you may need to wait for the cylinder to refill and reheat if it is empty.
Conventional boilers are the least expensive to replace Not as energy efficient as combi boilers – heat is lost from hot water in the cylinder
Works well with low mains water pressure If you don’t already have cold water and expansion tanks, it can be costly to install
Solar compatible Requires space for the tank and boiler system
Back up – if the boiler breaks, and you have an electrical immersion heater installed in the cylinder, your home will still have access to hot water

System boilers

Similar to conventional boilers, system boilers need a hot water cylinder. Unlike conventional boilers, there isn’t the need for a cold water tank, and pumps and valves – which are separate in conventional boilers – are built-in with a system boiler. Both types work in similar ways, but system boilers are essentially a more modern unit.   

Best for:

  • Homes already suited to conventional boilers
  • Don’t have low mains pressure
  • Have a modern central heating system
Pros Cons
Space saving when compared to conventional boilers Doesn’t work well if the water pressure isn’t reasonable
No need for any components to be installed in the loft Take up more space in the home compared to a combi boiler
Easy installation when compared to conventional boilers since there are fewer parts to fit Hot water supply is limited to how much hot water is in your cylinder – when it runs out you will have to wait for the tank to heat back up

What size boiler do you need?

Installing the right size boiler will ensure there’s enough hot water supply and central heating to heat all your rooms efficiently. It’s important to know the system size that will suit your home, which you can work out by counting the number of radiators that your home has. 

  • 24kW to 27kW for up to 10 radiators
  • 28kW to 34kW for 10 to 15 radiators
  • 32kW to 40kW for 15 to 20 radiators

Based on the house size and the average number of radiators, these are the recommended system sizes.

House size Central heating output needed
Flat 24kW or below
Bungalow 24kW to 27kW
Terraced 26kW to 29kW
Semi-detached 28kW to 34kW
Detached 32kW to 40kW

What’s the best type of combi boiler? –
David Hilton, Energy and Renewables Expert

david hilton

This is entirely dependent on your household’s requirements. Combi boilers work by lifting (heating) water by 35C at a given flow rate. For example, a 24kW boiler will lift 11l per minute by 35C. If there is low water pressure at the property or resistance in the pipes, or the boiler has to push the water to a higher floor, then the flow rate will be affected. A combi boiler should not be installed so that the outlet water (shower or bath taps) is any more than one floor above the boiler.

Your choice of combi boiler can be down to brand, installer or budget. In hard-water areas, I prefer simple boilers with fewer parts. They may potentially be very slightly less efficient on paper, but the total cost of ownership over its life may be a lot more affordable.

Another influence on the choice could be the compatibility with home controls. Many boiler manufacturers have their own room controls. If you already have those, then you will need to stay on brand and make sure the new boiler is still fully compatible with the existing controls. There is, however, a generic control software called OpenTherm. Many boiler manufacturers and control manufacturers have adopted this open-source software so the boiler and the controls can ‘speak’ to each other. If you have OpenTherm controls, then you ideally need an OpenTherm-compatible boiler.

How to replace your boiler

Replacing your boiler can seem like a daunting task if you don’t know what to expect or where to begin. To start off with, you’ll want to consider the size, type and even price range for your new boiler. It’s best to compare as many quotes as you can to get the best deals; this also includes considering warranties and other features like smart controls. Here’s our step-by-step guide to replacing your boiler from quote to installation. 

  1. First, you’ll want to choose your new boiler. It’s important that you go with a model with the right capacity for heating output and water flow for your home. With that being said, you’ll want to refer back to our boiler size section. 
  2. Next, you’ll want to get a free quote. You can find free quotes on most UK boiler brands – we advise that you get between three and five quotes to make sure you have the best deal for you. 
  3. Once you’ve selected the quote that you’re happy with, someone will contact you to arrange an installation date and explain what the process will involve – on average it usually takes three days after this phone call for installation to take place.  
  4. On the day of installation, water, electricity and gas supplies are isolated. Gas Safe engineers will lay down a protective cover to preserve your flooring and carpets. 
  5. Remove your old boiler – the old boiler fittings are removed and there will be no extra cost for this, providing there are no issues. 
  6. Install the new boiler – engineers will test the gas supply and suitability of the wall for the boiler fitting. Pipework will be altered if needed and extra brackets fitted if required. The new unit is then fitted and electrical work is carried out to connect it to your central heating. 
  7. Cleansing your system – the new system undergoes a chemical cleanse, getting rid of unwanted waste materials and deposits; this takes a few hours to complete. 
  8. If you’ve chosen to have a smart thermostat, it’s installed at this stage. Once installed, your engineer will demonstrate how to use it.
  9. The last safety checks are now performed by your engineer to make sure your boiler is safe and ready to use. 
  10. Lastly, your engineer will register your manufacturer’s guarantee – make sure you check this step has been completed.

How long will it take to install a new boiler?

The time that it takes to install a new boiler will largely depend on if it’s a straightforward like-for-like switch (meaning your old boiler is the same type as the replacement).

If your replacement boiler is the same type as your old one and you are having it installed in the same location, then it should take between one and three days, but most likely it will be completed in one to two days if there are no problems. 

If you are switching types and your new boiler requires additional parts like a water cylinder, then it could take upwards of three days. Changing the fuel type generally takes between two and three days, and if you want to change the location of your boiler, you’re looking at between three and four days. Your installer will explain how long they expect it to take before they get started.

What are the best boiler brands?

The UK has a number of leading boiler brands that manufacture combi boilers, system boilers and conventional boilers. 

Market leader Worcester Bosch is one of the UK’s better-known boiler brands and is best known for its high-end quality units and long product warranties. Worcester Bosch, with over 60 years of experience, manufactures combi, system and conventional boilers and covers all fuel types. Worcester’s boilers have a range of system sizes, and the brand receives a 4.6-star rating on Trustpilot.   

German manufacturer Viessmann is a reliable brand with long-lasting and energy-efficient products. The widely respected brand was founded in 1917 and has since grown into an international household name. The brand scores a four-star rating on Trustpilot. Viessmann’s combi, system and conventional boilers support different fuel types and the company has strongly emphasised smart controls, which are part of its bid to reduce environmental impact.  

Vaillant is one of the UK’s leading boiler brands that is known in 20 countries and has a history of providing heating systems for more than 141 years. Vaillant’s products are energy efficient and aim to keep energy bills low and carbon footprints to a minimum. The brand has developed a range of ecoTEC boilers with built-in smart features that automatically reduce heating when needed. Vaillant achieves a 4.5-star rating on Trustpilot

Ideal Heating has provided good quality boilers in the UK for over 100 years and receives an impressive 4.8-star rating on Trustpilot. Ideal Heating’s combi, system and heat-only boilers all come with long warranties of between seven and 12 years. Its products are manufactured in the UK and are sleek and modern by design.  

Baxi is a UK manufacturer with a range of combi, system and heat-only boilers powered by mains gas or LPG. Its warranties range from two to 10 years, so this isn’t an area in which we’d say it excels. However, its boiler ranges are some of the most affordably priced on the market and this applies to multiple system sizes. Customers who’ve chosen Baxi have contributed to its 4.5-star Trustpilot rating.

New and replacement boilers Q&A

The average cost of a replacement boiler is £1,200 without installation costs, or £1,900 with installation. This is the average price for straightforward installations – if you are changing the location of your boiler in your house or switching system types, you will likely pay more than this.

If your replacement unit is a like-for-like switch, it should take between one and three days to install. If you’re installing a new boiler that is a different type, then it could take upwards of three days depending on the complexity of the job.

New A-rated boilers are cheaper to run than older models with lower energy efficiency ratings. This is because less energy is lost – with an A-rated unit you can be sure that 90 per cent or more of the energy is being used to heat your home.

Boilers have an average lifespan of between 10 and 15 years, although they can last longer than this. Once past their lifespan, their efficiency will begin to decrease, so it’s advised that you replace your boiler every 10 to 15 years. You should replace it as soon as possible if you notice your energy bills increasing unexpectedly, water leaks, or if it’s suffering from frequent breakdowns.

A modern A-rated boiler could shave up to £840 off your energy bills annually. By replacing your old boiler with a new one, your home will be more energy efficient and benefit from less energy loss.

New boilers are more energy efficient than older ones; you only have to look at their energy efficiency rating to find this out. Most modern units are rated A, which means their energy efficiency is 90 per cent or higher. When compared to older G-rated boilers, which suffer from up to 30 per cent heat loss, new models come out on top.

Your boiler should be serviced once a year. Having it serviced regularly can help identify any major problems before they manifest into a system breakdown. Servicing also gives you peace of mind and will tell you if it is running safely and efficiently.

It’s not advisable to install your own boiler, particularly if it is run on gas. It is incredibly dangerous for individuals who are not trained and could lead to things like gas leaks, carbon monoxide poisoning or explosions. It will also invalidate your boiler warranty and may not comply with building regulations.


Rachel Sadler

Home Tech Writer

Rachel is a seasoned writer who has been producing online and print content for seven years. 

As a home tech expert for Independent Advisor, Rachel researches and writes buying guides and reviews, helping consumers navigate the realms of broadband and home security gadgets. She also covers home tech for The Federation of Master Builders, where she reviews and tests home security devices. 

She started as a news and lifestyle journalist in Hong Kong reporting on island-wide news stories, food and drink and the city’s events. She’s written for editorial platforms Sassy Hong Kong, Localiiz and Bay Media. While in Hong Kong she attended PR events, interviewed local talent and project-managed photoshoots. 

Rachel holds a BA in English Language and Creative Writing and is committed to simplifying tech jargon and producing unbiased reviews.

david hilton

David Hilton

Energy and Renewables Expert

David Hilton is a Director at Heat and Energy Ltd, and an expert in conventional and sustainable building, energy efficiency services, and healthy homes. In his role at Heat and Energy, David supports projects from design brief to completion with technical, sustainability and strategic advice. He also advises on building fabric and heating, including conventional, modern and alternative systems.

As an expert in energy efficiency and sustainable building, David has a masters degree in sustainable architecture and is a regular contributor to Homebuilding & Renovating, Selfbuild and Design, Grand Designs, and Build It magazines, The Metro and The Independent newspapers as well as various trade magazines.

David is also a member of professional bodies and organisations including Gassafe and the Gloucester Design Review Panel.

David is a frequent speaker on heating, renewables and modern building methods at the Homebuilding and Renovating shows as well as training installers of heat pumps, photovoltaics, and solar thermal systems. In addition, he delivers courses and seminars at the National Self Build and Renovation Centre.