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Worst Boilers: Which brands lost in 2021 and why

In the market for a brand spanking new boiler? If you want the best, go for a Worcester Bosch.

If, for some reason, you want to know about the worst, read on.

How we wittled down the worst boilers

To keep things unbiased, there's many ways to carry out a fair comparison between boilers, so, in the interest of objectivity, here are the factors we considered: 

  • Which? Annual Boiler Survey Results 
  • Warranty period offered by the brand 
  • The overall reputation of the brand based on customer reviews 
  • TrustPilot reviews  
  • Awards and accolades e.g. Which? Best Buy Awards
  • Customer service performance 
  • The price range of their boilers  
  • Efficiency ratings

Which? Annual Boiler Survey Results 

Which? Worst Boiler Results

The trusted name in consumer research, Which?, carry out an annual boiler survey (that's every year), totting-up survey results from over 12,000 boiler owners and 166 heating engineers, combining both the daily user experience and the expert opinion. 

Which? Boiler Survey

In total, the survey considers and provides a final aggregated score for the following: 

  • Reliability score 
  • Customer score 
  • Engineer recommendation 
  • Build quality 
  • Availability of parts 
  • Ease of fixing faults 
  • Ease of servicing 

No other organisation surveys and collects so much data about plain old boilers, so, you can trust Which?.

So, what did this year’s survey results show? Which boiler was the worth of boast worlds?

Based on the survey results, there was a clear loser – Ferroli boilers.

Ferroli Worst Boiler

Based in Burton-on-Trent, this Italian brand received a low score of two out of five from consumers and just one star from engineers. The brand also received three out of five for reliability.

Overall Reliability 3/5
Engineer Score 1/5
Consumer Score 2/5

Overall Ferroli landed an overall score of just 35%, significantly lower than any other boiler brand, including Vokera, who came second to last with an overall score of 50%. 

Ferroli Worst Boiler HEIn particular, the review of the Ferroli HE 27C, highlighted no positives at all, furthermore, other models offered by the manufacturer include HE 32C and the HE38C.

Combined, these combi boilers are officially the worst boilers rated and reviewed by the trusted consumer organisation. 

Worst for Boiler Efficiency 

A boilers efficiency rating relates to how much 'energy efficiency' is the percentage of the total energy used by the boiler to provide useful heating.

Worst Boiler Efficiency

An efficient boiler will save the planet, and money. It's a cliché win-win.

Central heating boiler efficiency is categorized using a system called the Energy related Products (ErP) rating system, where A represents the most efficient to G, representing the worst efficient. 

Boiler Efficiency Rating ChartSince 2018, Boiler plus legislation has meant that all new boilers are required to be at least 92% efficient. This means that no matter which brand boiler you select, it will always be at least 92% efficient. 

Essentially, this means that in terms of efficiency, there is very little difference between new boilers.

There really is no worst. Sorry.


Worst Boiler Warranty 

The boiler manufacturer’s warranty is one of the most important considerations when looking for a new boiler.

Worst Boiler Warranty

As a general rule, the length of a warranty reflects the quality of the boiler, but it is also worth mentioning that the level of support can vary. That is why it is important to check customer reviews, to get an insight into what their breakdown experience when under warranty was like. 

Is your boiler's warranty worth the paper it's written on?

Boiler manufacturers do not typically offer the same warranty period for all of their products, but they typically begin at around 1 year.

The aim is to purchase a boiler that comes with a warranty that lasts as long as possible, obviously.

Worcester Bosch Best 10 Year Guarantee

Currently, Worcester Bosch offers one of the best warranties of any manufacturer. Not only is it a 10-year warranty (if purchased through Heatable), but it is a guarantee. 

Boiler Guarantee, Boiler Warranty...What's the Difference? 

A guarantee is an agreement from the brand that they will attend to your property and repair or replace the condensing boiler within a reasonable timeframe. 

Most other brands just offer a warranty as standard, this is an agreement to investigate the problem, but is not an unconditional agreement to fix or repair it for free.

We guarantee Worcester Bosch offer the best guarantee

Worst Boilers by Price 

The cost of the boiler is an important consideration, but ultimately, it is never a good idea to buy the cheapest, since the Which? survey results show you may be trading off quality, reliability and much more. 

Buy cheap, buy twice?

Worst Boilers by Price

With that said, here is a list of some of the most popular boiler brands with a list of their typical price ranges.

Bear in mind that this is for the boiler only and does not include installation costs

Learn all about combi boilers in our what is a combi boiler guide. 

  Price (Boiler Only)  Brand Type
Vokera Compact 25 £500 Budget
Ferroli Sky Eco £417 Budget
Heatline Capriz 24 £460 Budget
Alpha E-Tec 28 £700 Middle Range
Vaillant EcoTEC Pro 28 £1,034 Middle Range
Viessmann Vitodens 050 £850 Middle Range
Worcester Bosch Greenstar £970 Premium


As can be seen in the table above, the cheapest boilers are offered by Ferroli and Vokera, while Viessmann, Worcester and Vaillant are the most expensive.

There is a clear trend that the manufacturers with the best reputation and reviews by Which? are more expensive, so in the case of boilers, it is definitely worth paying a little more. 


So, which boilers do Heatable recommend? 

Now we have discussed some of the worst boilers available, based on a variety of different factors, you are probably wondering which boilers are the best? 

For the full, detailed analysis, check out our best boiler manufacturers guide and best combi boilers article

Essentially, the best boilers available are the ones that are reliable, offer longevity and a warranty period that provides long term peace of mind. 

Worcester Bosch Boilers Best

Worcester Bosch boilers ranked top of our list for several reasons, not only have they been a Which? Best Buy awards winner for 10 consecutive years, but they offer an unrivalled 10-year guarantee (not just a warranty). 

Combine that with their excellent guarantee offer, customer service and easily sourced parts and you have the best boiler brand in the UK.

Get a fixed price on a new Worcester Bosch Boiler, online.

Worst boiler conclusion & some key takeaways:

If you are looking for a new boiler, it is important to consider the cost of installation and any other associated work you may require. 

The good news is that we offer a fixed price for the complete installation, that includes the boiler and installation

Use this clickable form to get a fixed price on the screen instantly. 

At Heatable, we fit new boilers from as little as £1,545, all over the UK.

What's more, as we've already covered, our boilers come with warranties which are up-to 10 years long. That's loooooong.

What's even more, we're able to offer low monthly payments with boiler finance, and even interest free options.

Get a fixed quote on a new replacement boiler in 60 seconds, here.

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Heatable is registered in England and Wales No. 08804726 (VAT No. GB205805920 ). Trading address is 1 Station Road, Great Sankey, Warrington, Cheshire, WA5 1RH. Heatable acts as a credit broker (not as a lender) and offers credit products through a panel of lenders. Heatable is authorised and regulated by the Financial Conduct Authority (reference no. 805259).

[1] Price based on a like for like combi swap in a 2 bed, 1 bathroom terraced home with a standard flue

[*] Installation dates are subject to installer availability

[ยน] only available on combi boiler installations

Financial Support: If you are in receipt of certain benefits, you may be entitled to claim a free boiler grant.