The best 40kW combi boilers are well suited to larger homes with 2-3 bathrooms and around 20 radiators.

While system or regular boilers are the more common heating systems for these property types, the high 40kW output rating gives homes with higher heating and hot water demands the chance to benefit from these cost-effective, space-saving units. A number of industry leading manufacturers have released premium models which means you have plenty of choice when it comes to finding the best 40kW combi boiler:

1. ATAG i40C
2. Baxi 800 Platinum+
3. Ideal Vogue Max
4. Navien NCB
5. Potterton Titanium
6. Worcester Bosch Greenstar 8000 Life
7. Worcester Bosch Greenstar 8000 Style

---

 

---

Is a 40 kW combi boiler suitable for my home?

Rather than storing water in a cylinder, like a system or regular boiler, combination boilers deliver instant hot water on demand using water from the mains. Due to this, they’re typically better suited to smaller homes with a single bathroom. Should you be looking for a more spacious option then a combi boiler is the perfect boiler type.

Thanks to the high output rating, a 40 kW boiler is capable of providing hot water to more than 2 bathrooms at the same time while also heating around 20 radiators. If there are 3 or more bathrooms in your home then it’s likely to be better suited to a system boiler.

Don’t make this decision yourself, instead hire a Gas Safe registered engineer to take a look around your property and give their expert recommendation. You can get free quotes from heating engineers based in your area using Boiler Guide.

Best 40 kW combi boilers

If a Gas Safe registered engineer recommends a 40kW combi boiler for your home then you’re in luck, as there are plenty of premium models available on the market.

Best 40kW Combi Boilers	Seasonal Space Heating Efficiency	ErP Rating	Warranty
ATAG i40C	94%	A	10 years
Baxi 800 Platinum Plus	93%	A	10 years
Ideal Vogue Max	93%	A	10 years
Navien NCB	93%	A	7 years
Potterton Titanium	91.1%	A	7 years
Worcester Bosch Greenstar 8000 Life	94%	A	10 years
Worcester Bosch Greenstar 8000 Style	94%	A	10 years

ATAG i40C

For homes with more than a single bathroom the ATAG i40C is a powerful option as it has a high hot water flow rate. It’s also incredibly efficient, which will help to lower your energy bills and you’ll be well covered by a lengthy 10 year warranty.

• Achieves an A+ efficiency rating when used with the ATAG One Zone controller
• Lifetime replacement guarantee on the iCON stainless steel heat exchanger
• Features a weather compensator that automatically adjusts the flow temperature depending on the conditions outside
• Compact dimensions of 700 x 440 x 355mm (HxWxD) make it an ideal boiler for homes that don’t have much space to spare
• High flow rate of 16.2 litres per minute (at 35°C temperature rise)
• Endorsed by the Energy Saving Trust

The ATAG range also includes output ratings of 24 kW, 28 kW and 36 kW.

Baxi 800 Platinum Plus

Baxi are a well recognised boiler manufacturer, especially amongst installers. The Baxi 800 Platinum Plus is well suited to larger homes and runs very efficiently to help lower your energy bills.

• OpenTherm technology allows you to take control from your smartphone or tablet
• A flow rate of 16.4 litres per minute at a 35°C temperature rise makes it well suited to homes with multiple bathrooms
• Built-in frost thermostat for protection from freezing through the winter months
• Can be installed with multi-fit flue kits to offer more flexible installation
• Energy Saving Trust endorsed

In addition to the Platinum+, the Baxi 800 range includes combi boilers with output ratings of 25 kW, 30 kW and 36 kW.

Ideal Vogue Max

Ideal Boilers are well known for manufacturing premium products and their Vogue Max range is no different. Only the best components have been used within this boiler and Ideal clearly has plenty of confidence in it as the warranty can stretch to up to 12 years.

• The warranty period can be extended from 10 to 12 years when installed by an Ideal Max accredited installer
• Boiler frost protection to keep the unit running in even the coldest of conditions
• As a combi boiler with low lift weight the installation is made much simpler, which could save you money when it comes to hiring an installer
• In the unlikely event of a fault, the LCD display shows clear text messages to describe the issue

Should your heating engineer recommend a lower output, the Ideal Vogue max range includes combi boilers with outputs of 26 and 32 kW.

Navien NCB

Navien might not have been around for as long as other boiler manufacturers to feature in this list but their NCB combi boilers can compete with even the most well established brands.

• Offers great flexibility with where to install the boiler thanks to ‘class leading’ flue lengths
• Flow rate of 16.4 litres per minute (35°C temperature rise)
• Fitted with primary and secondary stainless steel heat exchangers which helps to extend the life of the boiler
• Should an error occur, Navien boilers have a quick and clear message that will help you to understand the issue and get it back up and running

There are 3 more models in the Navien NCB range, should you have a lower demand for heating and hot water, with output ratings of 24, 28 and 34 kW.

Potterton Titanium

The Potterton Titanium has proved to be a favourite amongst families looking for an efficient heating system that can deliver central heating and domestic hot water on demand.

• Flue lengths of up to 20 metres which will give you greater choice when it comes to finding a location for the boiler
• Stainless steel heat exchanger for increased efficiency and low risk of corrosion
• High flow rate of 16.4 litres per minute
• 24-hour clock which gives you control over when the boiler is used (not all boilers have a clock as standard)
• Energy Saving Trust endorsed

There are also 28 kW and 33 kW output ratings in the Potterton Titanium range.

Worcester Bosch Greenstar 8000 Lifestyle

The Greenstar 8000 Lifestyle range from Worcester Bosch includes Life boilers (30 – 50kw) and Style boilers (30 – 50 kW). One of the main differences is that Style boilers are available in black and white, while Life units only come in white. Whether you have a Life or Style boiler installed, they share a number of industry-leading features:

• Fully compatible with Bosch EasyControl which allows you to control the heating and hot water from your phone – you don’t even have to be in the house
• 1:10 modulation to increase efficiency during operation

Should you be looking for an even more powerful combi boiler, the Worcester Bosch Greenstar 8000 Lifestyle range also includes 50 kW models too:

• Worcester Bosch Greenstar 8000 Life 50kW
• Worcester Bosch Greenstar 8000 Style 50kW

---

 

---

How much do 40kW combi boilers cost?

Combi boilers are often the most affordable boiler type, mainly because there’s no need for any external tanks or cylinders. It could be possible to find a 40kW combi boiler for no more than £1,500.

Best 40 kW Combi Boiler	Potential Cost (excluding installation)
ATAG i40C	–
Baxi 800 0Platinum Plus	£1,200 – £1,500
Ideal Vogue Max	£1,350 – £1,400
Navien NCB	£900 – £1,000
Potterton Titanium	£900 – £1,000
Worcester Bosch Greenstar 8000 Life	£1,175 – £1,300
Worcester Bosch Greenstar 8000 Style	£1,250 – £1,400

These potential costs don’t include installation, which you’ll also need to consider. All heating engineers have their own prices which can vary depending on the type of boiler being installed, the complexity of the installation and even where you live (London tends to be the most expensive).

To give yourself the best possible chance of getting the most competitive price for your combi boiler installation, we highly recommend comparing multiple quotes. And thanks to Boiler Guide, finding heating engineers has never been easier. Simply complete our online form, letting us know about the job you need carrying out, and you’ll get free quotes from up to 3 local heating engineers.

How do combi boilers work?

Combi boilers take water from the mains and heat it as and when the central heating or domestic hot water is needed. This removes the need for any cylinders or tanks, helping to save space around the property.

Find out more about combi boilers in:

• What is a Combi Boiler?
• Combi Boilers: Costs, Benefits & Savings

Best combi boilers for off-grid homes

Not all properties are connected to the gas network which means that off-grid homes will need a boiler that runs on a fuel that can be stored onsite. Fortunately, some of the best 40kW combi boilers are LPG compatible (a gas that can be stored locally).

Best 40 kW Combi Boiler	LPG Compatible?
ATAG i40C	Yes
Baxi 800 0Platinum Plus	No
Ideal Vogue Max	Yes
Navien NCB	Yes
Potterton Titanium	No
Worcester Bosch Greenstar 8000 Life	Yes
Worcester Bosch Greenstar 8000 Style	Yes

Oil is another option for properties that aren’t connected to the gas network, and there are a number of options available that will be able to meet the same heating and hot water demands as a 40kW combi boiler.

Oil Combi Boilers (35 – 42 kW)	Output Rating	Efficiency	Warranty	Potential Cost (before installation)
Firebird Envirogreen Combipac HE C35	35 kW	93%	2 years	£2,500 – £2,750
Grant Vortex Pro External	36 kW	94.5%	2 years	£1,875
Mistral Combi Standard C4	41 kW	87%	2 years	£2,160

If you plan to have an oil boiler installed, then you will need to hire an OFTEC registered heating engineer. You can get free quotes from heating engineers in your area by going through our simple online form.

---

 

---