What Is A Condensing Boiler?

Condensing boilers are considered to be some of the most efficient boilers out there on the market and are effective at heating people’s homes without impacting the planet or costing too much to run.Review of the Best Condensing Boilers of 2022 and Beyond (By Brand)

what are the 5 best boiler brands on the market?

1 – Worcester-Bosch Combi Boilers

2 – Viessmann Combi Boilers

3 – Vaillant Combi Boilers

4 – Alpha Combi Boilers

5 – BAXI Combi Boilers

Best Condensing Boilers (By Model)

Best Condensing Boilers – Conclusion

Advantages of Condensing Boilers

Condensing boilers are super clever, super at saving energy and super at saving money.

Considering condensing?

Here are the best condensing boilers of 2021, as according to Boiler Comparison website Let’s heat recent review:

Did you know that every year, more than 1 million new boilers are installed into UK homes?

That’s an incredible amount of boilers, and thanks to the introduction of ‘Boiler Plus’ legislation back in 2005, all new installs are now condensing boilers that are a huge improvement on the inefficient non-condensing models of the past. 

But what exactly are condensing boilers?

Condensing boilers are water heaters fuelled by gas or oil. These boilers achieve a high-efficiency level (typically greater than 90% on the higher heating value) by condensing water vapour in the exhaust gases and so recovering its latent heat of vaporisation, which would otherwise have been wasted.

This condensed vapour leaves the system in liquid form, via a drain.

In many countries, the use of condensing boilers is compulsory or encouraged with financial incentives.

And how do you know why condensing boiler to choose?

See the summary of the Let’s heat article and guide for the best Condensing Boilers of 2021, 2022 and Beyond.

Review of the Best Condensing Boilers of 2021, 2022 and beyond (By Brand) 

To determine the best boilers available in 2021 and beyond, Let’s heat considered the following factors: 

  • Warranty period offered by the brand 
  • The overall reputation of the brand based on customer reviews 
  • The brands Trustpilot reviews  
  • Awards and accolades e.g. Which? Best Buy Awards etc.
  • Customer service performance levels 
  • The price range of the boilers  
  • Boiler efficiency ratings

Based on the results, here are the top 5 best condensing boiler brands in the UK right now (on 2021 results):

  1. Worcester Bosch Combi Boilers
  2. Viessmann Combi Boilers
  3. Vaillant Combi Boilers
  4. Alpha Combi Boilers
  5. BAXI Combi Boilers

Review of the Worcester Bosch Combi Boilers (Best)


One of the UK’s most well-known and trusted boiler manufacturers, Worcester Bosch remains a favourite among professional Boiler installers and heating engineers.

Why did Let’s heat think Worcester-Bosch deserved the number one spot? 

  • Which? Best Buy Award for 10-years running 
  • 10-year guarantee
  • Availability of parts is second to none 
  • Excellent customer reviews & aftercare
  • High-efficiency A-rated combi boilers 

Review of Boiler Model: Worcester-Bosch Greenstar i


The Worcester-Bosch Greenstar i is officially Worcester’s best selling combi boiler range having sold and installed more than 1 million of them in the UK alone. 

Suitable for small to medium-sized homes on a budget the Greenstar i is the brand’s entry-level offering and the range includes the 30i i.e. 30kW and the less powerful Greenstar 25i at 25kW

Although not the brand’s best offering, it still boasts some great features, not least of which is an A-rating for efficiency, a user-friendly digital display and a reassuring ‘Which?’ Best Buy Award.

Review of Boiler Model: Greenstar CDi Compact Boiler