Best Condensing Boiler


“According to experts, the best condensing boiler is…” Great research! We will be talking about this much-requested topic today on Suner’s blog. We will make a valuable comparison of condensing boilers, which will be very useful if you are thinking of purchasing one, or simply so that you are well informed about the most current dynamics of the heating market. As we will also insert a couple of summary tables with this information, and a section of frequently asked questions on the subject, reading this article will be very practical for you.

What is a condensing boiler and how does it work?

A condensing boiler is heating equipment designed with the ability to reuse the latent heat in combustion fumes. It’s high-tech manufacturing (the most effective today) allows it to generate even more heat thanks to an intelligent process of recycling the steam from combustion that it has just carried out but without the need to use more fuel to do so.

A condensing boiler is capable of reaching up to 110% energy efficiency (as we will see in some of the models included in this article). How do you achieve such a high rate of fuel efficiency? Its technology is basically watertight, but it goes further.

By means of special components, it causes recirculation of the combustion gases before they go out into the atmosphere. It then reduces the temperature of the gases to the dew point level, extracts the water vapor from them, and reuses it to generate more hot water without using more fuel.

These characteristics make the condensing boiler the most efficient and the least polluting of all the boilers on the market today.

(More details in our articles on the subject. Links are at the end.)

What is the best brand of condensing boilers?

It can hardly be said that there is a single brand of condensing boilers that is the best of all. That there is a better brand is a fairly relative issue. This must be seen in relation to the needs of the family in terms of:

  • Number of inhabitants of the house.
  • Number of services that the boiler will provide.
  • Type of fuel with which it works.
  • Availability of said fuel where you live.
  • Hardness of the water in the region.
  • Flow of water entering your house.
  • There are some other factors as well.

Based on all this, each household must choose which is the best boiler. However, keep in mind that, according to a comparison of condensing boilers carried out by the OCU, the best condensing boilers for the 2020-2021 period were from the Cointra brand (we will see details about this in the next heading of this same article). Vaillant, Junkers, Baxi, and Ferroli also scored very good marks.


In addition to what we have just said, we can offer you a list of the most purchased and installed boiler brands. It will be for a reason, so take note. Here is the list, which is by no means exhaustive, and is not even organized by relevance but rather in alphabetical order:

  • Ariston
  • Baxi
  • Chaffoteaux
  • Cointra
  • Ferroli
  • Junkers
  • Saunier-Duval
  • Vaillant
  • Viessman

What are the best boilers according to the OCU?

The OCU (Organisation of Consumers and Users) is a Spanish organization that aims to defend the rights of consumers. The information it publishes about the products on the market is almost always of great practical use.

Now we will look at the top 10 condensing boilers according to the OCU for the period 2020-2021 in Spain. These results have been taken from the comparison of condensing boilers carried out by said organization and published in its October 2020 magazine. Along with each model, we will detail the general rating it received:

  1. Cointra Superlative Condens 25 C boiler: 74 points
  2. Cointra Superlative Plus boiler: 73 points
  3. Vaillant EcoTec Pure boiler VMW 236/7-2: 72 points
  4. Junkers Cerapur Excellence Compact ZWB 25/28 boiler: 71 points
  5. Baxi Neodens Plus 24-24 F ECO boiler: 70 points
  6. Ferroli BlueHelix Tech RRT 24 C boiler: 70 points
  7. Vaillant EcoTEC Plus boiler VMW 246/5-5: 68 points
  8. Boiler Ariston Clas One 24: 66 points
  9. Chaffoteaux Pigma Advance boiler: 65 points
  10. Boiler Saunier Duval Thelia Condens 25: 64 points

(If you want to know more details about the results of the OCU report on the best boilers for the 2020-2021 period, follow this link to a page on the organization’s official website.)

Boiler Cointra Superlative Condens 25 CMaximum saving mixed boiler.26.5 kW power.Energy efficiency of up to 108.8%.ErP compliant: consumption reduction of up to 30%.
Boiler Cointra Superlative Plus 24 CPower: 24kw.Instant production of DHW.Class 6 NOx.It comes ready to work with NG or LPG.
Boiler Vaillant EcoTec Pure VMW 236/7-2Power of 18.5 kW (heating) 24 kW (DHW).Save up to 30% energy.Compact design and reduced dimensions.Class 6 NOx.
Junkers Cerapur Excellence Compact ZWB 25/28 BoilerMixed boiler by micro accumulation.Power from 25 to 28 kW (heating and DHW).94% energy efficient and low NOx.Compatible with solar heating system.
Boiler Baxi Neodens Plus 24-24 F ECOIncludes inverter technology for gas.Ability to easily switch between types of gas.Intelligent digital operation.Class 5 NOx.
Boiler Ferroli BlueHelix Tech RRT 24 CHigh aesthetic design (intakes covered by the casing).With an anti-reversal valve (suitable for collective systems in overpressure).Class 6 NOx.94% energy efficiency.
Boiler Vaillant EcoTEC Plus VMW 246/5-5Power of 24 kW (DHW) and 20 kW (heating).Instant hot water thanks to the intelligent micro-accumulation system.Energy efficiency of up to 110%.Class 6 NOx.
Boiler Ariston Class One 24Modulating technology with a high degree of efficiency.Instantaneous DHW (stainless steel exchanger with increased section).Energy efficiency of up to 110%.Energy classification of A+.
Chaffoteaux Pigma Advance BoilerMixed boiler by micro accumulation.Power of 22 kW (DHW) and 26 kW (heating).Class 6 NOx.Modulation of 1:7 and energy efficiency of up to 110%.
Boiler Saunier Duval Thelia Condens 25Mixed boiler with power of 25 kW.Compact design but with high performance.Energy efficiency of up to 104%.Ultra-quiet operation.


How much does a condensing boiler cost?

We cannot give a single price as an answer to the question: How much does a condensing boiler cost? since this varies from one brand to another, and the prices of different models from the same brand are even different. So, what we will give will be a price list of the best-rated models according to what we have been discussing in this article:

Caldera Cointra Superlative Condens 25 C850 €
Caldera Cointra Superlative Plus670 €
Caldera Vaillant EcoTec Pure VMW 236/7-2860 €
Caldera Junkers Cerapur Excellence Compact ZWB 25/281300 €
Caldera Baxi Neodens Plus 24-24 F ECO643 €
Caldera Ferroli BlueHelix Tech RRT 24 C667 €
Caldera Vaillant EcoTEC Plus VMW 246/5-51190 €
Caldera Ariston Class One 24675 €
Caldera Chaffoteaux Pigma Advance630 €
Caldera Saunier Duval Thelia Condens 25850 €

What is better: condensing or a sealed boiler?

Condensing boilers are better than sealed boilers in many ways: they reuse heat through a condensing process, thereby achieving exceptional levels of fuel efficiency, minimizing polluting emissions, and reducing fuel bills. Let’s look at a little more detail on this.

A condensing boiler is always a sealed boiler, but not vice versa: not all sealed boilers are condensing. A sealed boiler is a boiler whose combustion chamber is completely hermetic and isolated from the environment where it is installed. This determines that both the air for combustion and the expulsion of residual gases travel through tubes hermetically connected to the boiler from the outside, either separately or in a coaxial or concentric design (one tube inside another).


A condensing boiler must also comply with all these sealing characteristics, but it adds something essential that a sealed boiler does not have: it is capable of reusing the latent heat in the exhaust fumes, thereby helping to reduce the exhaust temperature, reducing consumption of fuel, minimises environmental pollution in terms of gases and heat, and helps you to pay lower bills.

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