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Last updated: 10 October 2023

40kW Boilers – Everything You Need to Know

A 40kW boiler is a particularly good fit for large homes as it can run up to 20+ radiators. So you shouldn’t need to worry about heating up your home.

Deciding on a new boiler for your home can be stressful with all the different factors you have to take into consideration. One of the most important factors to keep in mind is the output size. If you’re looking for a 40kW boiler then you’ve come to the right place. In this article we’ll talk you through the different types of boilers and models available in 40kW.

But if you’re still not sure what size of boiler you need then don’t worry. In the table below you can get a better idea of which output size you’ll need for your home:

No. of RadiatorsCombiSystemHeat-only
Up to 1024-27kW9-18kW9-18kW
Up to 1528-34kW18-26kW18-26kW
Up to 20 (and over)35-42kW27-40kW27-40kW

As well as the output size and type of boiler, you also need to think about the efficiency rating and warranty length. This is why it’s important to compare multiple 40kW boilers to ensure you’re getting a model that best suits your needs.

Last but not least, you’ll also need to compare prices. But where do you even begin with this? How are you meant to know if you’re getting a bargain or being scammed? This is where GreenMatch comes in. We have a large network of qualified heating engineers across the UK, which means we can easily connect you with reliable installers available in your area so you can objectively compare their rates.

By clicking the button below, you’ll receive up to 3 free boiler quotes from different installers, which you can then compare to ensure you’re getting the best deal possible. What’s more, you’re not obliged to accept any of the offers you receive, so you have nothing to lose. Click the button below to get your free quotes and have your new 40kW boiler installed in no time.

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40kW System Boilers

If you have a large home with a high energy demand then a system boiler is likely to be a great choice. System boilers are some of the best boilers for large houses because they work alongside a separate water cylinder which enables them to deliver greater volumes of hot water.

Below we’ve listed some of the best system boiler options available in this size for you to consider, including a 40kW oil boiler for those who don’t have access to the gas grid.

1. ATAG I40S 40kW System Gas Boiler

ATAG is well-received by its customers, being one of the best-rated boiler brands on Trustpilot UK. ATAG offers high-quality boilers including the I40S 40kW system gas boiler. This model is also available in output sizes 32kW, 24kW, 18kW, and 15kW.

Some of the key features of this boiler include user-friendly controls so you can easily oversee your home’s heating needs. It is also highly reliable, with ATAG offering a warranty up to 14 years and even a lifetime replacement guarantee on the boiler’s heat exchanger.

  • Efficiency: 94%
  • LPG Compatible: Yes
  • Central Heating Output: 38.8kW
  • Warranty: Up to 14 years
  • Estimated price (excl. installation): £1,510 (inc. VAT)

2. Vaillant ecoTEC plus 637 System Gas Boiler

Vaillant is a popular brand amongst homeowners in the UK. Even though Vaillant doesn’t have any boilers with exactly 40kW as an output, its ecoTEC plus boiler with 37.6kW should still easily meet your heating and hot water needs. This model is also available in 48kW and 64kW if you are in need of more power, as well as a range of smaller output sizes.

Many of the components of this boiler, such as the pump and expansion vessel, are built into the unit itself. This will make the installation process easier and quicker. Some other standout features of this boiler include frost protection, so it can function at an optimum level all year round, and its own app so that you can control your heating even when you’re not at home.

  • Efficiency: 94%
  • LPG Compatible: No
  • Central Heating Output: 37.6kW
  • Warranty: 10 years
  • Estimated price (excl. installation): £1,537 (inc. VAT)

3. Mistral Sealed System CS4 41kW Oil Boiler

If you live in a large home and aren’t connected to the gas grid then a system oil boiler is likely to be one of the most accessible and suitable options for you. Even though oil is not the best fuel type for the environment, this Mistral sealed system CS4 boiler comes with a high efficiency rating to make sure you’re getting the most out of your fuel and money.

This model is also available as an outdoor unit, and in output sizes 20kW, 26kW, and 35kW, so you’re likely to find something that fits your home’s needs. It is also designed to fit under a standard kitchen worktop and has a white casing to blend in with kitchen appliances.

  • Efficiency: 93%
  • LPG Compatible: No
  • Central Heating Output: 41kW
  • Warranty: Up to 5 years
  • Estimated price (excl. installation): £3,200 (inc. VAT)

As you can see the prices of boilers can vary depending on factors such as the fuel type and brand. Installation rates can also vary massively depending on your location, how complicated the installation is, and your installer’s rates.

In this regard, one of the best and easiest ways to lower the costs and avoid being overcharged is to compare quotes from multiple heating engineers. This means you’ll be able to find the best deal and save money, especially on installation.

Finding quotes from qualified heating engineers can take up hours of your time and a lot of effort, but don’t worry! We can help make the process much quicker and easier for you. Simply click the button below and we will find up to 3 quotes from Gas Safe Registered engineers. You’re under no obligation to accept any of the offers and it’s completely free of charge.

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40kW Combi Boilers

Combi boilers are the most popular type of boiler in the UK–and for good reason. They are compact and don’t require an extra hot water cylinder in your airing cupboard or a water tank in your attic, saving you plenty of space. Combi boilers are able to provide hot water on demand, meaning you can have a shower without waiting for the water to heat up.

Combi boilers typically have smaller output sizes compared to other types of boilers, making them more suitable for small- and medium-sized homes. However, with that being said, there are still 40kW combi boilers available that can run up to about 20 radiators.

We’ve put together a list that includes the best combi boiler of 2024 in 40kW from some of the most well-known boiler brands:

1. Baxi Platinum+ 40kW Combi Gas Boiler

Baxi is a British company which not only produces high-quality boilers but also takes into account its environmental impact, by taking steps to reduce its carbon emissions, waste, and noise pollution.

This model is available in 40kW (for domestic hot water output) and is perfect for homes with high hot water demands. This boiler is also highly adaptable as it has a built-in frost thermostat and is compatible with weather sensors, so you can ensure that your boiler is working efficiently no matter the weather.

  • Efficiency: 93%
  • LPG Compatible: No
  • Central Heating Output: 34.4kW
  • Domestic Hot Water Output: 40kW
  • Warranty: 10 years
  • Estimated price (excl. installation): £1,307 (inc. VAT)

2. Ideal Vogue Max C40 Combi Gas Boiler

Ideal is another British brand with over 100 years of experience. With this boiler, Ideal focuses on stylish composite design as well as making the interface user-friendly. As it is a single unit with a low lift weight of 35.4kg, it should be quick and easy to install.

The 40kW model is perfect for homes with a high hot water demand, however, if you’re questioning whether you need this much power for your home, then there are also 26kW and 32kW (hot water output) versions of this model available.

  • Efficiency: 93%
  • LPG Compatible: Yes
  • Central Heating Output: 32kW
  • Domestic Hot Water Output: 40kW
  • Warranty: Up to 12 years
  • Estimated price (excl. installation): £1,323 (inc. VAT)

3. Worcester Bosch Greenstar 8000 Style 40kW Combi Gas Boiler

Worcester Bosch is a brand which consistently comes out on top, winning awards again and again. This particular 40kW model is part of its energy-efficient Greenstar range which has won the Which? ‘Best Buy’ award for multiple years in a row.

This model is also available in 30kW, 35kW, 45kW, 50kW, so if you think you might need something slightly less or more powerful than a 40kW then this model has you covered. And as the name suggests, “style” was taken into account when designing this boiler, as it is available in 2 high-gloss colours (black and white).

If you’re just going to put your boiler in a kitchen cupboard, then chances are you might not care too much about the style aspect. Worcester Bosch also has another combi boiler model called Greenstar 8000 Life, which has many of the same features as this boiler and is on average cheaper.

  • Efficiency: 94%
  • LPG Compatible: Yes
  • Central Heating Output: 35kW
  • Domestic Hot Water Output: 40.8kW
  • Warranty: Up to 12 years
  • Estimated price (excl. installation): £1,625 (inc. VAT)

As combi boilers are highly popular in the UK, this means you’re likely to find a high-quality one to suit your needs. This is great, however, the models mentioned above are only just the tip of the iceberg of what options are out there. It can be overwhelming researching boilers with seemingly small differences between them, trying to figure out which is best for your home.

This is why it’s important to seek advice from not just one, but multiple heating engineers.

This way you can not only ensure that you’re getting the best advice, but it also enables you to compare quotes and get the best installation price when you decide to fit your new boiler.
Researching boilers on your own can be stressful and time consuming, and the same goes for finding qualified heating engineers available in your area.

Thankfully, we can take this task off your plate. By clicking the button below we can provide you with up to 3 free quotes from qualified heating engineers who can help you with any boiler-related queries you may have.

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40kW Heat-Only Boilers

A heat-only boiler, which is also known as a regular or conventional boiler, is the oldest type of boiler mentioned in this article. However, that doesn’t mean they are no longer being produced; you can still find modern models from top brands on the UK market.

There are some things you need to know about heat-only boilers before you install one. Firstly, they typically take up a lot of space in your home as they require both a water tank in your attic and a hot water cylinder in an airing cupboard.

Secondly, because of these extra components, the installation process can be complicated and expensive. Therefore, heat-only boilers are not usually recommended by heating engineers unless you are replacing an old heat-only boiler with a new one.

If you’re looking for a heat-only boiler replacement then you can check out this list of some of the top heat-only boilers to give you a better idea of what 40kW options you have:

1. Worcester Bosch Greenstar 8000 Life 40kW Heat-Only Gas Boiler

Here we have a Worcester 40kW heat-only boiler – another boiler from its award-winning Greenstar range. It has many of the same features as the combi boiler we mentioned above, and is also available in output sizes 30kW, 35kW, 45kW, and 50kW.

These Greenstar boilers are available with Worcester’s longest ever guarantee, so you can feel assured of your boiler’s reliability. Furthermore, they are also able to wirelessly connect to Worcester’s smart thermostat, so you can easily keep track of how much energy you’re using.

  • Efficiency: 94%
  • LPG Compatible: Yes
  • Central Heating Output: 40kW
  • Warranty: Up to 12 years
  • Estimated price (excl. installation): £1,776 (incl. VAT)

2. ATAG iR40 40kW Heat-Only Gas Boiler

Another great boiler from ATAG is the iR40 heat-only boiler. If you’re still unsure about whether a 40kW boiler is a good fit for your home, then you also have the options of 32kW, 24kW, 18kW, and 15kW for this specific model.

One of the main benefits of an ATAG boiler is that it boasts having the lowest NOx (nitrogen oxides) emissions in Europe, making them relatively better for the environment. The iR model is also fully compatible with solar thermal hot water systems, meaning you don’t have to rely solely on gas.

  • Efficiency: 94%
  • LPG compatible: Yes
  • Central Heating Output: 38.8kW
  • Warranty: Up to 14 years
  • Estimated price (excl. installation): £1,390 (incl. VAT)

3. Mistral Kitchen Utility Classic CKUT4 41kW Heat-Only Oil Boiler

Again for those who don’t have access to the gas grid, there is also a heat-only oil boiler from Mistral you can consider. Like the system boiler mentioned above, even though oil is not the best fuel for the environment, the boiler’s condensing technology at least ensures that the boiler works as efficiently as possible.

The 40kW model will likely meet your heating needs, however, if you think your home needs something less powerful then there are also 20kW, 26kW, and 35kW options you can look into. Some of the main benefits to this boiler are that it is quiet during operation and an outdoor model is also available if you prefer this.

  • Efficiency: 92%
  • LPG compatible: No
  • Central Heating Output: 41kW
  • Warranty: Up to 5 years
  • Estimated price (excl. installation): £2,800 (incl. VAT)

If your boiler is already about 10 years old it’s likely that its efficiency rating has dropped significantly from when you first got it. This means you’ve probably noticed your energy bills rising. One way to double check if your boiler needs to be upgraded is by checking its energy-efficiency label. Preferably, you want an A-rated boiler. A modern A-rated boiler could save you up to £630 a year, compared to an older G-rated boiler (Energy Saving Trust, July 2023).

We can help you find a modern highly-efficient boiler and save money in the process. By clicking the button below you’ll receive up to 3 free quotes from qualified heating engineers. This way you’ll be able to compare them and choose the best price for your new A-rated boiler. It takes less than a minute, and you’re under no obligation to accept any of the quotes you receive.

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FAQ

Bronte McClelland
Written by Bronte McClelland, Writer

Brontë is an experienced writer and editor for GreenMatch. Her passion for sustainability and renewable energy drives her to stay at the forefront of green-energy trends.

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