First Published: September 21, 2020. Updated: May 1, 2023
We understand that for most people buying a new combi boiler can be daunting – so, we’re happy to help you with the ins and outs of a boiler replacement.
In this guide, we’ll offer you boiler replacement advice and teach you basics to ensure you understand the different types of models available and the costs involved – and, even walk you through the installation process.
Combi boilers have a lifespan of 10-15 years. If your unit is approaching this age, It might be time to consider booking a replacement. After all, no one wants to be stuck with a broken boiler.
To determine whether it is time to replace your boiler or if your current boiler can be repaired, consider the following points:
Have you called out an engineer more than once in the last year? If you’ve answered yes, then it’s worth contemplating whether the amount of the repairs is greater than the cost of a new boiler. Based on research we have undertaken over a 6 month period, it is likely you will spend between £500 – £1000 on an old boiler across multiple breakdowns.
Most boiler breakdowns are caused by wear and tear, and corrosion of the internal components.
If you believe your boiler breakdown isn’t caused by something quite so major, the below article may be of assistance.
However, if you’ve tried all those and more, it’s pointless to keep paying your hard-earned money on fixing a boiler which is losing you money on energy bills over the short term and long term. Investing in a new boiler can ensure headache-free heating and hot water, as it will be backed up by a comprehensive warranty.
Your boiler was manufactured before 2005
Regulations state that all gas-fired boilers fitted since 1st April 2005 have to be condensing boilers, and all oil-fired boilers fitted since 1st April 2007 have to be condensing boilers. These regulations apply to new boiler installations and boiler replacements.
If your existing boiler was installed before 2005, it is unlikely to be a condensing boiler. This means that your current boiler will let exhaust gases escape through the flue. Hence, wasting energy that can be recovered. Hot steam contains energy, and modern condensing boilers harvest that energy by recycling the hot exhaust gases through the primary heat exchanger first before they exit through the flue outside. The below diagram explains how a condensing boiler works:
Your energy bills are increasing
If you’ve noticed a sudden surge in your energy bills. Then your boiler could be to blame. As boilers age, they tend to lose efficiency, causing your energy bills to increase.
Another thing to bear in mind is that your system may require cleaning to get rid of magnetite sludge which can also add to the cost of your bills
Replacing an old, unreliable model with a new A-rated boiler will ensure you keep energy bills to a minimum. Most modern boilers are A-rated and if you combine your boiler with smart thermostats you can boost the overall efficiency of your system.
According to the Energy Saving Trust, you can save up to £500 per year on energy bills by replacing your old boiler with a modern condensing boiler. We go into the cost savings a new boiler can provide later in this guide.
Your current boiler no longer meets your needs
Is your boiler struggling to meet hot water or heating needs. Then, you may require a boiler with a higher kW output. Another option could be to consider going to a new design, such as a system boiler and hot water cylinder or a storage combination boiler.
Your current boiler is leaking
Simply put, a leaking boiler is never a good sign. In fact, it indicates there’s a crucial issue with an internal component. A heat exchanger, valve or seal may have broken, these can be expensive to fit – in most cases it will be cheaper to install a new one. Especially if the heat exchanger has completely failed.
Your current boiler smells odd
If you smell an eggy odour when you use your boiler, there’s could be a gas leak. The only time a boiler emits an odour is when there is something wrong with it and this could potentially be dangerous. Immediately turn off the gas meter and call the emergency gas line on 0800 111 999. Then get in touch with a registered Gas Safe engineer. Do this if you ever detect any unusual smells emanating from your boiler.
In this situation, you should avoid using any electrical appliances or switches, and you should try to ventilate your property.
Your pilot light is glowing yellow/orange
If your boiler is running properly, the pilot light flame should always be blue. If the flame appears yellow, it may be a sign of carbon monoxide and has the potential to be dangerous.
Carbon monoxide is an odourless, colourless gas that can be lethal. If it fills your home and you breathe it in, it can cause carbon monoxide poisoning and replicate symptoms similar to the flu. These symptoms include:
- Fatigue/lethargic Feeling
Carbon monoxide is often a result of too much air getting into your boiler system. As carbon monoxide is odourless it’s not immediately obvious, other signs of carbon monoxide include soot or staining around the boiler and high levels of condensation in the room.
If you suspect a carbon monoxide leak in your home, call the National Gas Emergency Service on 0800 111999 to report the problem.
National Gas Emergency Service
You can call 0800 111 999 24 hours a day, 7 days a week.
Gas Safety Advice Line: 0800 300 363
Gas Safe Register: 0800 408 5500
The costs for replacing a boiler will differ, but a straightforward boiler replacement will typically cost around £1800 to £4000.
Storage combis and more technically advanced boilers ie: Viessmann Vitodens 200-W range will typically be on the higher end of the stated range.
Below is an estimated cost of a gas boiler replacement in a home with 3 bedrooms. All of the values in the table are averages and could go up or down depending on several factors. These include:
- Boiler type
- Installation (what work is required)
- Rates charged by the installer
|Boiler type||Average cost of boiler excluding installation||Average labour cost of boiler installation||Approximate total cost of boiler fully installed|
|Combi||£600- £2,000|| £1,000||£1,200 – £3,000|
|System||£500 – 2,000||£500 – £1,000||£1,000 – £3,500|
|Conventional||£500 – 2,750||£500 – £1,000||£1,000 – £3,750|
*This does not include the cost of the hot water cylinder
As multiple factors can have an impact on boiler replacement costs, all of the costs in the table are approximations. To get a more exact idea of boiler replacement costs, we highly recommend using our online quote tool. This takes into account factors such as your budget, home size and central heating/hot water needs, to provide you with a more realistic estimate of installation costs.
It’s important not to confuse boiler-only costs with full boiler installation costs. When you’re looking to buy a boiler online, you will find a number of online plumbing merchants such as:
- Mr Central Heating etc
The above examples sell boilers and other central heating extras online, the prices listed on these websites are for boilers on a ‘supply-only’ basis. Often they will be combined with flues and other extras, but these prices do not include installation. These are plumbing merchants, and you can buy boilers at affordable prices. But to install them, you will need to find Gas Safe registered and manufacturer accredited installers or a local plumber. Do not try to install a boiler yourself unless you’re Gas Safe registered, as this is illegal and can result in a large fine or even a prison sentence.
A boiler replacement from Boilerhut will comprise the following:
- A brand new, condensing boiler
- A horizontal or vertical flue
- A microbubble deaerator (if required)
- A magnetic filter
- A limescale filter
- A Boiler Plus compliant programmable thermostat or an internet-enabled learning thermostat
- A north-facing weather compensation unit (if compatible)
- A chemical flush and an approved inhibitor
- All required pipework
- Extended manufacturers’ warranty
- Commissioning of the boiler and benchmark testing
- Building regulation notification with certification including landlord certificates
- Handover and induction on the boiler, controls and best usage
Combi to Combi Swap
Whether your central heating system runs on mains gas, LPG or oil, a combi to combi swap is probably the easiest and quickest boiler replacement.
Combi is short for combination. If you’re new to the world of combi boilers, and want to understand what a combi boiler is and how they work, please click the links below to read the in-depth posts chock-full of useful information:
Replacing an old combi boiler with a new combi boiler, even with gas run upgrades and extras, takes a day or two.
System Boiler Replacement
A system boiler has an external unvented DHW (domestic hot water) storage cylinder installed elsewhere in the house, usually in the airing cupboard. Because of the hot water storage, system boilers are suitable for larger properties, or if you have more than two bathrooms in your house. A system boiler doesn’t require attic tanks to store cold water like a regular boiler does.
System to Combi Conversion
The system boiler and cylinder is removed and replaced with a combi boiler along with gas-run upgrades if required.
There are larger capacity combi boilers available these days, so it is possible to replace a central heating system with a hot water cylinder with just a combi. Furthermore, if your property is large enough for a system boiler and not small enough for a combi, but you don’t have space for a DHW cylinder, don’t fret. Luckily in 2018, we have combi boilers with a storage tank available now.
Read more about them here: Storage Combi Boiler
To find out which type of boiler is best for your property, the following post has some great information: Which Boiler is Best
Regular/Conventional/Open Vent Boiler Replacement
This is the default setup for most medium to large properties in the UK. As mentioned above, on top of a DHW storage cylinder, a regular boiler has cold water tanks usually in the attic space as well. These are great if you have a fairly large house with multiple bathrooms.
Regular/Open Vent to Combi Conversion
For this type of boiler replacement, the boiler along with attic tanks and any hot water cylinders are removed and possibly recycled or just discarded as scrap. A gas run upgrade to 22mm is carried on, required in most cases for a combi boiler. And the whole system is flushed (chemical or power) before installing a new combi boiler.
Buying a new boiler involves a bit of research, as you’ll need to understand the type of fuel your boiler runs on, which boiler model will suit your home and the best boiler size (kW output rating) for your heating and hot water requirements.
What size boiler do you need?
Determining the right boiler size can be difficult. So, we’ve crafted the grid below to help you make sense of the different output ratings. Typically, residential boilers have an output rating of 24 kW and 42 kW, and you can use the number of radiators and bathrooms in your home to determine the right boiler for your home based on the output ranting.
|Property size||Output rating|
|1-2 bedroom, 10 radiators, 1 bathroom||24-30kW|
|3-4 bedroom, 15 radiators, 1-2 bathroom||30-35kW|
|4+ bedroom, 20 radiators, 2+ bathroom||35-42kW or storage combi|
Choosing a boiler size
It’s vital that you choose the correct boiler size for your home, or you might find yourself with inefficient heating and hot water. Read our article: What Size Boiler Do I Need? to discover the right size boiler for you.
Still not sure? Don’t worry – we’re here to help. Take our free, online quoting tool to help you discover the correct boiler size for your home, and the costs involved in fitting it. Bonus! You’ll be one step closer to getting a new boiler – Hurrah!
What’s the best fuel for my boiler? Generally, gas is the most popular choice for UK homeowners. Why? Because gas is the cheapest per kWh compared to Oil or LPG.
Here’s a quick break down of different fuel types:
Gas is around 3 to 4 times cheaper per kWh than other fuels, making it an economical choice to heat your home. However, it does require a connection to the gas network, meaning it can cost for first-time grid connections. Most towns and city locations are all on gas grid.
If your home isn’t connected to the gas network, installing an oil boiler can be a more cost-effective solution, although it is more expensive to install and ongoing service and maintenance is more expensive than a gas or LPG boiler. Oil is also not supplied by the gas or electric mains – instead, oil is stored in a tank, meaning you need to ensure it has a sufficient amount of fuel to run your boiler.
A LPG boiler works in a very similar way to both natural gas and oil boilers i.e. the boiler burns the fuel to produce the energy needed to heat water from the mains supply.
How to find out which fuel your boiler uses
In most cases, if you’re already living in a property, then you’ll most likely know the fuel type you have. However, if considering purchasing a new home and don’t have any experience with an off-grid property, you’ll need to research what fuel type the current boiler requires. You can do this on the EPC register, where you can download a document that gives you suggestions of how to improve the overall rating and efficiency of your property which ultimately if followed will reduce your overall energy spend.
The location of your new boiler
If your boiler is an eyesore? Or, you are just looking to free up space? In any case, the location of your boiler can rapidly change the aesthetics of a room. So, make sure you select a spot that you’re happy with – ultimately, it’s going to be there for up to a decade.
Generally, the kitchen will be the most popular location for a boiler, however, other popular places can be an old airing cupboard or a garage. If space is an issue people do install boilers in lofts – there are some downsides to having a boiler installed in a loft; especially if it is a combi or system boiler. Usually, we would always recommend that you leave the boiler in the current location.
In most cases, boilers can be relocated. However, there may be many technical reasons why this would become difficult. Also another thing to consider is that moving a boiler can increase the overall cost of the installation.
Depending on the layout of your residence, relocating your boiler could generate a faster response to hot water demand, and increase your house mark interest – after-all, no one wants to buy or rent a house with a boiler in the bedroom.
If you really need to move a boiler we would suggest that you discuss this in detail with a professional plumbing and heating firm to fully understand all the technical issues involved with moving the boiler as a first point of any extensions or building works to fully understand all implications.
Another thing to bear in mind is new boiler locations can differ depending on the type of boiler you choose, as some are wall-mounted, floor mounted, and some will require a cylinder and storage combis have a larger physical size than standard combi boilers
Moving a boiler can cost around £300 to £800 on average, and 1 day to be installed. However, these costs can range depending on the labour involved.
How much is a boiler installation?
Installation prices can vary based on the complexity of the job. So, to help you gauge potential payments, we’ve drawn up two scenarios below show you the rough costs for:
1) Replacing a boiler in its current location
2) Rough cost for fitting a boiler in a new location
Here is a scenario that shows the rough costs for fitting a new combi in the same location and for installing a new combi in a location. However, the cost of moving the boiler will differ according to where it is moved to.
Installation prices can vary based on the complexity of the job. So, to help you gauge potential payments, we’ve drawn up two scenarios below to show you the rough costs for:
1) Replacing a boiler in its current location
2) Rough cost for fitting a boiler in a new location
|Installation of a new combi boiler||Approx cost with mid range boiler||Time taken|
|1) Replacing an existing combi boiler|
with a new boiler
|2) Replacing an existing combi boiler|
with a new boiler
To move boiler £300 additional each item 1 – 1.5 days to install.
The cost of replacing a system boiler can vary depending on whether you’ve opted for a like-to-like installation or a system change. Here are three scenarios to estimated cost:
As above – A – budget £1800.00 – mid range – £2100 – premium brand £2500.00
B – budget £3800 – mid range £4200 – premium brand £4500
C – budget £3700 – mid range £4100 – premium brand £4400
|Installation of a new system boiler||Approx cost with mid range boiler||Time taken|
|A) Replacing a system boiler with a new system boiler and retain the unvented hot water tank||
|B) Replacing a heat-only boiler and hot water tank with a system boiler and unvented hot water tank * based on a B or C rated cylinder||
|C) Replacing a combi boiler with a system boiler|
and unvented hot water tank
Based on a B or C rated cylinder
Like the above, the cost of replacing a conventional boiler can largely depend on the type of installation and labour required to complete the job. We’ve listed three scenarios to help you understand potential costs for a like-for-like install, location change and system replacement.
A budget £1700 mid range £ 1900.00 – premium brand £2300
B budget £3300 mid range £3600.00 – premium range £3900
C budget £3700.00 mid range £4000.00 premium range £4300
|Installation of a new system boiler||Approx cost with mid range boiler||Time taken|
|A) Replacing an existing heat only boiler|
with a new boiler
|B) Replacing an existing heat only boiler and new cylinder||£2,200||2 days|
|C) Replacing an existing combi boiler and with a conventional boiler and cylinder plus attic tanks||£3,200||2-3 days|
C – why would you do this? The reason would most likely be if mains pressure is very low or too many bathrooms. There are other solutions to increasing your water flow rate and pressure. If you want to add a move boiler – average cost is £300.
The cheapest option would be to place the new boiler in the same location as the old one, as it requires less installation time and less materials.
Upgrading your old, inefficient boiler for a new, condensing model will save you money with every year that passes. The Energy Saving Trust states that you can save up to £330 a year by switching your boiler. Let’s take a deeper look at how much money you can save.
The chart below, shows estimates for a typical A-rated boiler operating at around 90% efficiency and shows how it saves compared to an outdated model. Why not check your current property’s efficiency by entering your postcode? Try it here.
|Efficiency of old boiler||% saving||£ saving|
As you can see, the more inefficient your old boiler is, the more you can save by replacing it. In turn, replacing an old boiler will also help you save on breakdown costs. You can also boost efficiency further by using a smart thermostat.
Want to get a quote for a more efficient, condensing boiler? Then, why not try our free online quote tool to get a realistic estimate of potential replacement costs.
Most people think a condensing boiler is a new type. However, that couldn’t be further for the truth. In fact, it’s the technology inside your boiler, that makes it condensing. For example, you still choose from a combi, system or conventional, but will have the efficiency increased by the condensing technology. Modern condensing boilers get the highest energy efficiency ratings, saving you money and reducing your carbon footprint.
The benefits of upgrading to a condensing boilers
Upgrading your outdated system to a modern, efficient condensing boiler comes with a whole host of benefits, including:
Less energy consumption
A condensing boiler will be around 40 – 15 % more efficient than an old boiler. Meaning, you’ll benefit from reduced energy bills, and fossil fuels.
Condensing boilers are a lot safer than non-condensing models. This is because there is lower risk of carbon monoxide problems and breakdowns.
Less fuel waste means a lower carbon footprint. Every condensing boiler installed saves around 1.7 tonnes of CO2 every year, helping you reduce your carbon emissions and do your bit for the environment.
Space saving construction
Your condensing boiler is likely to be smaller and more sleek than an outdated boiler. There is no need to find space for a hot water tank either.
Boiler costs vary depending on the type you need, the capacity and the efficiency rating. Usually, A-rated boilers cost more than lower efficiency models. However, you’ll benefit in the long run as they’ll save you more on your heating bills.
As a rough guide, for a budget boiler you’ll be looking at around £600 for the boiler only. Standard, mid-priced boilers can cost from around £600 – £850, and should guarantee a life expectancy of 7 to 10 years. Whilst, with premium brand boilers you can expect to pay £1200.
When choosing the right boiler option for your home, there are three types to choose from:
- Compact size; a good choice for smaller properties
- No separate water tank required
- Cheaper installation
- Provides on-demand hot water from the mains
- Typically suitable for medium size and large homes
- No loft tank, which saves space
- Doesn’t need a feed or expansion cistern makes them more efficient
- Offer a constant supply of hot water to any number of taps
- A great choice for homes with high hot water demand and low mains pressure and flow rate
- Suitable for large households with two or more bathrooms
- Requires a cold water storage tank in the loft as well as a hot water tank
Unless you have ornate or double panel radiators, the basic radiators in your home can be calculated at an average of 1.2 kW per radiator. To determine the boiler output needed for your home, we multiply the number of radiators you currently have by 1.2. By undertaking this calculation, we are able to size a boiler for your home.
Below, we have included a list of typical boiler sizes and the homes that they are suitable for.
- 24-25kw – Suitable for smaller properties with 1-3 bedrooms, and up to 10 radiators.
- 28-30kw – Suitable for slightly larger properties with up to 4 bedrooms and 15 radiators.
- 33-35kw – Suitable for big houses with 6-7 bedrooms and about 20 radiators.
- 40kw and above – Suitable for large properties with close to 10 bedrooms and 20 radiators.
Kilowatt output may differ for different boiler types – for example, combi, system etc.
With so many boiler manufacturers out there, it can be hard to understand which one is right for you. Here are a few of the UK’s leading brands:
An industry leader in both pioneering technology and German design. These boilers are built with reliability, high efficiency and usability in mind. They are fast becoming one of the most popular brands in the UK, due to their sleek design and quality engineered products offering up to 10-year warranty.
A good, strong brand with a long track record of delivering high quality products. These boilers tend to be quiet and highly efficient, although some reviewers comment that the controls are a little confusing to use. Generally considered to be top of the range, you’ll pay a bit more for that Worcester Bosch badge.
The other ‘top of the range’ supplier, Vaillant boilers have been around for decades. They aren’t the cheapest option, but you are buying into a company who are also producing well engineered products.
Overall these boilers are good value for money. A handful of customers have had issues with breakdowns, but have been delighted with their included five-year parts and labour guarantee.
A solid mid-range boiler, this is a brand which offers a good half way price point between the Bosch/Viessmann and the Glow Worm. They have a reputation for excellent reliability, and have plenty of high efficiency A-rated models.
These boilers have a strong reputation for being reasonably priced, and compared to some of the other big names they do offer amazing value for money. The company also has lots of good feedback in terms of their customer service.
The real budget choice, these boilers are pretty much the cheapest out there, and are not renowned for longevity or reliability. However, they are still a popular choice for tenanted properties and second homes, owing to their amazing value purchase price.
Before selecting a manufacturer, we would advise you to do some comparative research. Looking at the customer reviews, warranties and benefits for each brand.
You can use customer reviews to determine what’s brand is best for you. Start by looking at sites such as; Trustpilot and Which? to find the ratings for specific boiler models.
Generally speaking, all new boilers come with a warranty from the manufacturer. This means that you can get your boiler repaired free of charge, during the warranty period. These can range from 2 to 10 years, depending on the installer.
At Boilerhut being a premium installer, we can offer 10 year warranties. Helping you keep your home warm, for less – find out more here.
Each boiler manufacturer has certain features and benefits that could be better suited to your home than another. So, it’s important to take time to read through boiler reviews to discover what works best.
Homes come in all shapes and sizes, meaning they have various hot water and heating demands. In turn, this can make it hard to determine what’s the best boiler for your home.
So, to help you discover the best boiler for your property. We’ve listed some of the best boilers on the market in 2020:
Viessmann Vitodens 200-W
Suitable for houses of all sizes, the Which? best buy winner Viessmann 200-W offers excellent reliability and usability. With 98% efficiency, this boiler is A-rated making it more economical to run.
Read more about the Viessmann Vitodens 200-W.
Worcester Bosch Greenstar 30i
Designed to meet the needs of small to medium homes, the Greenstar 30i is a compact system that can be installed in almost any location.
Read more about the Worcester Bosch Greenstar 30i.
Vaillant ecoTEC Plus
The Quiet Mark award winner, Vaillant ecoTEC Plus has a kW output starting from 25kW, making it ideal for small to medium properties.
Read more about the Vaillant ecoTEC plus.
Baxi EcoBlue Advance Combi
Endorsed by Energy Saving Trust, Baxi EcoBlue Advance Combi can meet the heating and hot water demands for any type of home.
Which would represent excellent value for money – while still having a stainless steel heat exchanger and considered a premium brand
Read more about the Viessmann 050-W.
It’s also important to compare output rating and whether a boiler is within your budget before selecting the model you want. Here’s a quick comparison form, to help you understand what boiler is best.
| Boiler name||Output range (Kw)||ERP rating|| Efficiency||Warranty|
|Viessman Vitodens 200-W||5.2 to 35||A-rated||98%||10 years|
|Worcester Bosch Greenstar 30i||24||A-rated||89.9%||10 years|
|Vaillant ecoTEC Plus||25 to 38||A-rated||89.3%||10 years|
|Baxi EcoBlue Advance Combi||24 to 40||A-rated||89.1%||10 years|
|Viessmann Vitodens 050-w||4.7 to 35||A-rated||98%||10 years|
10 years on most of these brands would be offered if the installer chosen is approved by the manufacturer.
Looking to discover more? Then, why not take a look at Best Combi Boilers 2020 in the UK.
How can I get a new boiler quote? Use our free, online quote tool to help gain a better understanding of the boiler installation costs. We’ll take into account factors such as the size of your home, heating and hot water needs, to give you a realistic estimate of your new boiler installation costs.
Once you’ve received your quote, our friendly team will be in touch to ensure you have chosen the correct options for your property if not they are on hand to assist with this and hopefully producing the correct quote to meet your requirements, with a recommendation of a suitable boiler type, brand and model. Then, they’ll book you in with a registered gas safe engineer to install your new boiler.
Once you have completed your purchase with Boilerhut which we believe is a simple and straightforward process, generally a date will be agreed for your installation, you will have confirmation of this sent via text and your gas safe installer will generally arrive on site between 8-9 am they then will review the work order provided and debrief you on what work will be completed prior to them unpacking the boiler and materials. Also at this time they will make a final assessment and survey to ensure the job can be completed as per the work order. Once this has been established the work will commence. All our installers are highly trained and respectful – operating under stringent guidelines to ensure safety and respect at all times.
Generally speaking, a boiler replacement can take anything from 1 to 3 days, depending on the amount of work required.
For example, a like-for-like boiler replacement takes around 1 day to complete. Whilst, an entire system upgrade – due to change to pipework, removal of the tanks in the loft and the installation of a new hot water cylinder – can take 2-3 days to finish.
A boiler replacement can also take longer if you’re planning to move the boiler to a new location, as new pipework is required. If your boiler is gas and it’s being moved further away from the gas meter, then a bigger gas pipe may need to be installed.