Best Condensing Boiler

If you’re looking for the best condensing boiler money can buy, this post may be useful. Maybe you’ve spent last year looking for best condensing boilers 2019 and still continuing the search in 2020, and if that’s the case, fanastic! However, before we get into the boiler comparisons and reviews, if you’re new to this, let’s first understand what a condensing boiler actually is.

We’d like to clear some of the confusion around condensing boilers, as clients have asked us if condensing boilers are combi boilers.  The following post explains this in detail: Condensing or Combi Boiler

In short, every boiler manufactured in 2020 is a condensing boiler, regardless of the configuration being Open Vent, Sealed System, or Combi.

If you’d like to know more the best condensing boilers, you can take a look at some of our previous blog posts as well:

Maybe you’ve already done the research and feel confident about choosing your new boiler. If this is the case, then well done!

At this point, the best thing you can do is to speak directly to an expert. For a free, no-obligation quote on your new boiler, call us directly on 029 2009 9898 or get an online quote by filling your postcode in below, then hitting the green button!

What is a Condensing Boiler?

How to condensing boilers work?

All boilers, whether non-condensing or best condensing boiler, have combustion emissions, like heated gases, pass through their heat exchangers, transferring the energy that’s generated to radiators or under-floor heating, which spreads heat around your house.  After this is done, the remaining combustion gases are released into the air outside through the flue, usually up through the roof or through the wall.

In older, non-condensing boilers, some portion of this heat is lost during this process, because along with the waste gases a large amount of steam that forms during the burning process (due to the water contained in natural gas in its initial state) is being pushed out.  The released steam carries an untapped amount of evaporation energy, that older, non-condensing boilers are unable to make use of.

Whether you buy a cheap or the best condensing boiler manufactured in 2020, it will recycle the water vapour through their primary heat exchangers, recovering latent heat of vaporisation.  This condensed vapour leaves the system in liquid form, via a condensate pipe into a drain.

For more information on ‘What is a condensate pipe?’, please click here to read our detailed guide.

Best Condensing Boiler Technology

Condensing boilers have a fan installed next to the heat exchanger working at variable speed.  For these to work at optimum efficiency, a condensing boiler houses a closed combustion chamber connected to a coaxial flue, so the combustion gases can pass through it.  Controlling the fan’s speed helps maintain an optimum combustion ratio of air and gas.  To minimize any heat loss from the flue gases, it’s important for the boiler’s heat exchanger to allow water vapor condensation.

Internal Boiler Fan Example

A condensing boiler works at its best when the heat exchanger surface is equal or below what’s called the dew point temperature.  Normally, the dew point temperature for natural gas is around 55 degrees Celsius.  And so, for the boiler to work in condensing mode, the temperature of the coolant in the return loop (when the coolant returns back to the boiler) should not exceed 57 degrees Celsius.

Save Money on Energy Bills with the Best Condensing Boiler

If properly installed, the best condensing boiler will not only heat your home and provide hot water consistently, but can also reduce your gas consumption by 20% to 25%.  According to the Energy Saving Trust, you can save anywhere between £300 to £500 per year on your energy bills by switching to the best condensing boiler along with other energy saving measures like draught proofing your doors and windows, insulating your walls, using smart controls or weather compensation etc.

Condensing Boiler Cost

Working out a condensing boiler cost is something you don’t have to do alone. By speaking to one of our in-house heating experts, you’ll receive reliable and trustworthy advice that can ensure you get a fantastic boiler for a reasonable price. To do so, you can either call us directly on 029 2009 9898 or get a FREE, no-obligation quote by filling in your postcode below and then hitting the green button…easy!

Alternatively, if you’d like more information on costs of a new boiler, please click here

How are the Energy Savings Calculated?

When you buy the best condensing boiler in 2020, you can rest assured in the knowledge that they will be at least 90% energy efficient out of the gates, and can go up to 94% energy efficiency with the help of programmable thermostats or internet enabled smart learning thermostats like Nest.  A premium, high end, top of the line condensing boiler like the Viessmann Vitodens 200-W can go up to an amazing 98% (and above) energy efficiency.

Need more information on the Vitodens 200-W boiler? Click here here to read our informative review!

Compared to this, older non-condensing boilers started at about 80-85% energy efficiency, and over years of daily use dropped down to 70% or even 50% efficiency.  That’s because the internal components of a boiler go through massive amounts of thermal stresses on a daily basis for years, resulting in corrosion which reduces the efficiency.  If your existing boiler is older than 12-15 years, chances are it’s a non-condensing boiler, and you may be paying more on energy bills than you need to.

In monetary terms that means for every £100 that you spend on your energy bills, with an older non-condensing boiler operating at 70% or 50% efficiency, you may lose £30 to £50.  And with a modern condensing boiler operating at 94% efficiency, you may lose only £6 for every £100 spent on energy bills. That’s a lot of money wasted that would otherwise be saved in a best condensing boiler.

Condensing Boilers are Kinder to the Planet

Because less heat is lost through the flue gases, you increase your energy efficiency and waste lesser energy by investing in the best condensing boiler.  So, on top of saving your hard earned money on energy bills, you’re also putting out fewer emissions into the atmosphere and being environmentally responsible.  A condensing boiler can go a long way in reducing your carbon footprint.  Your decisions today can determine what kind of planet you leave behind for your future generations.  And yes, every single person counts.  As Mahatma Gandhi said, “Be the change you want to see in the world.”

Quality of Internal Components

When the condensing process happens, which means after cooling the vapor turns into liquid, it releases an amount of thermal energy.  Older, non-condensing boilers were designed to avoid the condensation process.  A modern condensing boiler loves the condensing process.  The condensation happens in a state-of-the-art heat exchanger within a modern condensing boiler, which absorbs the heat and transfers it to radiators around your house.

Stainless Steel vs Aluminium for the Primary Heat Exchanger

The secret to exploiting condensation for energy efficiency has been known for a long time, but it hasn’t been implemented effectively in home or industrial heating appliances until the most recent technological innovations.  To maintain high efficiency for longer, the primary heat exchanger needs to be robust.  Boiler manufacturers in the UK use either aluminium or stainless steel for their heat exchangers.

Below is a graph that shows the longevity comparison between aluminium and stainless steel heat exchangers.  While aluminium starts off strong, it drops off massively in later years, whereas stainless steel maintains its efficiency:

best condensing boiler

It is no secret that stainless steel is much more durable, reliable and less prone to corrosion compared to aluminium.  Viessmann are one of the only boiler manufacturers in the UK who use a patented Inox-Radial Stainless Steel Heat Exchanger for their best condensing boiler range.  And because they manufacture it in-house, they are able to compete at the same price point as market leaders in the UK, despite having a technologically superior boiler.

They are also one of the 3 “Best Buy Boiler” award winners in the UK.  The other two being Worcester Bosch and Vaillant, both of whom use an aluminium heat exchanger.

For more information on your boiler’s heat exchanger and how it can help you save on your energy bills, please read our informative ‘What is a Heat Exchanger?’ blog post

Best Condensing Boiler 2020

1. Viessmann Vitodens 200-W

best condensing boiler, viessmann vitodens 200-w no. 1


Energy Efficiency: 98%

Approx. Price (Boiler Only): £1,400 inc. VAT

Approx. Price (Boiler + Installation): £3,000 inc. VAT

Available in Open Vent, System and Combi Versions

This is one of the, if not THE best condensing boiler money can buy in the UK at the moment.  It’s one of the most powerful residential boilers available, because it’s almost as powerful as a commercial boiler, and it’s made by Viessmann, a big player in the domestic boiler industry.  As we mentioned earlier in this post, this boiler goes up to a whopping 98% energy efficiency with a combination of high quality internal components, innovative engineering solutions, and Viessmann’s Weather Compensation. On top this, a new version of the Vitodens 200-w has been fitted with wi-fi capabilities, offering you a more streamlined, easy-to-user experience.

For an in-depth, factual review of this model, please click the following link: Viessmann Vitodens 200-W Review

Some key features of the Vitodens 200-W:

  • Up to 98% of the fuel used is converted into heat
  • Quiet operation thanks to low fan speed
  • Compact dimensions, only 450 mm wide
  • Easy to operate Vitotronic control unit with 5 inch colour touchscreen
  • Control via app and internet (with optional Vitoconnect 100 WLAN adaptor)
  • Energy efficiency class: A
  • Optionally available as combi (type BK2B) or system boiler (type B2HB)
  • System boiler: Cascade with up to six boilers up to 594 kW possible
  • Environmentally responsible MatriX cylinder burner
  • Optional remote fault notifications for Viessmann Trained Installers

2. ATAG iC Economiser Plus 35

best condensing boiler, ATAG

Energy Efficiency: 94%

Approx. Price (Boiler + Installation): £2,600 inc. VAT

Available in Open Vent, System and Combi Versions

A lesser known brand in the best condensing boiler space, ATAG is a Dutch manufacturer making some rumblings in the UK with their high efficiency boilers with a unique stainless steel heat exchanger.  Their primary heat exchanger condenses twice, which is why they can achieve a high energy efficiency figure of 94% and above.

  • Compact Dimensions
  • 10 year warranty
  • Instant hot water with pre-heat facility
  • Built in Passive Flue Gas Heat Recovery Device
  • Comes with an outside weather compensator as standard
  • Achieves ErP ‘A’ rating for heating and hot water
  • Savings of up to £40 a year on hot water and up to £320 off energy bills (Energy Saving Trust, April 2017).
  • Completely user friendly

3. Viessmann Vitodens 100-W

best condensing boiler, viessmann vitodens 100-w

Energy Efficiency: 92% to 94%

Approx. Price (Boiler Only): £1,200 inc. VAT

Approx. Price (Boiler + Installation): £2,600 inc. VAT

Available in Open Vent, System and Combi Versions

This is one of Viessmann’s highest selling boilers in the UK and rest of Europe and fits nicely between the entry level Vitodens 050-W and the high end Vitodens 200-W (number 1 in this list).

For an in-depth, factual review of this model, please click the following link: Viessmann Vitodens 100-W Review

Some features of this boiler:

  • Compact design and low weight
  • Quiet operation thanks to low fan speed
  • Available in outputs from 4.7 to 35 kW
  • High quality stainless steel Inox-Radial heat exchanger
  • Class A rated for energy efficiency
  • Low CO2 emissions for reduced environmental impact
  • User friendly Backlit LCD Touch screen for easy operation
  • Optional room thermostats available
  • Up to 10 year extended warranty available if installed by Boilerhut

best condensing boiler, vaillant ecotec plus with green iq combi

Energy Efficiency: 90% to 92%

Approx. Price (Boiler Only): £1,400 inc. VAT

Approx. Price (Boiler + Installation): £3,000 inc. VAT

One of the reasons why Vaillant and Worcester Bosch don’t score higher than Viessmann is because they still choose to use aluminium for their heat exchangers, instead of stainless steel.   This attempt from Vaillant in the best condensing boiler space has its merits.  It’s a high efficiency boiler and their lowest fuel consumption model.  Vaillant also claim 85% of its parts are recyclable at the end of its life.  This boiler can be programmed and controlled from your smartphone or tablet as well.

  • Quiet operation
  • Flow rate of 17.8 litres per min for fast instant hot water
  • ErP A rated for both hot water and heating efficiency
  • Dimensions in mm (43kW): W 720 x H 440 x D 474
  • Works with LPG where required

5. Viessmann Vitodens 050-W

best condensing boiler, vitodens 050-w

Energy Efficiency: 89% to 90%

Approx. Price (Boiler Only): £900 inc. VAT

Approx. Price (Boiler + Installation): £2,200 inc. VAT

For a detailed look at why the Viessmann Vitodens 050-W could be a fantastic choice of boiler for you, take a look at our review post or watch the video review below:



Viessmann’s entry level model in the best condensing boiler arena, it has surprisingly good performance at an incredibly affordable price.  What’s more, it has the same patented Viessmann stainless steel heat exchanger, and is also compatible with weather compensation.  And although it starts off at around 90% efficiency, with programmable thermostats and weather compensation it can go up to 92% to 94% efficiency, which is mighty impressive for its price.

  • Ultra Compact – Just 707mm in height
  • DHW output ratings of 5.9 to 35 kW
  • High quality stainless steel Inox-Radial heat exchanger
  • Integral instantaneous water heater
  • High efficiency – up to 97% (Hs) [gross cv]
  • Low CO2 emissions for reduced environmental impact
  • Digital user interface with LCD display for easy operation
  • Optional room thermostats, plug in time clock and wireless receiver 
  • Up to 7 year extended warranty available
  • Class A rated for energy efficiency

6. Worcester Bosch Greenstar CDi Classic

best condensing boiler, no. 5 worcester bosch greenstar cdi classic

Energy Efficiency: 89% to 90%

Approx. Price (Boiler Only): £1,200 inc. VAT

Approx. Price (Boiler + Installation): £2,500 inc. VAT

Worcester Bosch’s best model, while comparable to the Viessmann 050-W and 100-W in terms of efficiency, drops down in ranking due to Worcester Bosch continuing to stick to an aluminium heat exchangers.  Still great boilers and market leaders in the UK.  However, they’re great for the first 6 years or so and then drop down in efficiency as you can see in the heat exchanger comparison graph earlier in this post.

  • Low energy pump reduces electrical usage
  • Frost protection is included, reducing frost risk if installed in a garage or a loft
  • Larger two bathroom properties can be supplied by higher output options
  • Wide choice of controls enables greater comfort and economy
  • Instantaneous hot water, always available
  • Inbuilt keyless filling link making it easy to refill your system
  • Large Condensesure style siphon built into the boiler – eliminates frost risk

Buy the Best Condensing Boiler from Boilerhut

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For a free, no-obligation quote for your new boiler, enter your postcode below and hit the green button. Easy!

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