Eco Happy (Solar Expert)

Published February 28, 2024

We can safely say a heating engineer is not someone you want visiting you too often. Unfortunately, when you have a bad boiler, you may be forced to call a repairperson several times a year, or even a month!

Homeowners, tenants, and landlords who have been around the block know that some boilers perform like finely-tuned athletes while others are continually breaking down. You want to sidestep the latter sort smartly.

To help you avoid the worst boilers, we’ll highlight four brands with a reputation for shoddiness and why you should approach them with caution. To end on a positive note, we’ll refer you to a few top-rated performers.

Criteria We Used To Identify The Worst Boilers

How did Eco Happy judge the brands to find the worst boilers? Not wanting to prejudice any brand unfairly, we took a bunch of market information into account to identify consistent trends and feedback. In particular, we dug into the following:

  • Which? annual boiler survey results.
  • Feedback from our network of installers and heating engineers.
  • Feedback from our clients.
  • Our own market research, including articles and analyses by industry experts.
  • Customer reviews on Trustpilot (the leading review site).
  • We also considered price and warranty because these are often revealing quality indicators.

4 Boiler Brands To Avoid

Here are the brands that were consistently mentioned as the worst boilers.

1. Ferroli

Ferroli is an Italian boiler brand that has been in the business for over 50 years and has a UK presence in Derbyshire and Staffordshire. Ferroli boilers are regularly named as some of the worst around.

Here’s why you might want to think twice about getting one of these boilers:

  • The 2023 Which? survey shows a below-average owner’s satisfaction rating of 3 stars.
  • On Trustpilot, 25% of customers rate the company 3 stars and under. A sizable 21% award the brand a single star.
  • Common issues with the Ferroli boiler models include frequent leaking problems, delays in getting parts, inconsistency with hot water temperatures, and boilers suffering major breakdowns within a year or two of purchase.
  • There are countless complaints about poor customer service and delays in sorting problems.

Have a look at what reviewers say on Trustpilot:

  • “If I could put 0 stars I would!… Had central heating installed with a Ferroli boiler! The boiler has been constantly faulty and not worked correctly from 3 months after installation.”
  • “On the 23rd of December our boiler stopped working showing a fault code A08. Tried contacting Ferroli by phone to be told they are closed until 2nd January.”
  • “Ferroli gas water heater lasted just over two years before it broke. 16-week wait for a new electrode.”

Prices: Ferroli boilers are among the cheapest on the market, with a price range (excluding boiler installation) between £450 and £900. The adage ‘you get what you pay for’ seems appropriate.

Boiler warranty: Ferroli offers warranties between 1 and 5 years, depending on the model. This is a disappointingly short warranty period.

2. Keston

Keston, a UK manufacturer established in 1928, provides domestic and commercial heating installations and servicing. Since 2006, Keston has been part of Ideal Heating and operates out of Ideal’s manufacturing site in Hull.

While the feedback samples are small compared to other brands, Keston receives quite a battering.

  • From the 35 reviews on Trustpilot, a mammoth 68% of reviewers give the company only 1 star.
  • Common issues and complaints include continual error codes, low water pressure, heat exchanger problems, and overall unreliability. Many heating engineers regard the boilers as poorly made. Some engineers say they won’t come out to repair a Keston because the systems are so unreliable that they are afraid the boiler will break down again once they’ve left.

Here’s a sample of honest reviewer feedback:

  • “Our new home’s Keston boiler is a disaster. Christmas holidays have been ruined by this shoddy unit.”
  • “Problems all the time with some engineers not wanting to touch it. Recently it shut down and needs a PCB which costs nearly £500.”
  • “Absolutely useless service.”

Prices: From around £1,100 to £2,600. Consumers have expressed dismay at paying a lot for such an inferior product.

Warranty: Keston offers warranties from 2 to 7 years.

3. Vokera

Vokera was established 35 years ago and has bases across the UK and Ireland.

While not as bad as Ferroli or Keston, Vokera is also often named as a poor boiler brand.

Here are a couple of reasons why you should be cautious installing one of these boilers:

  • The latest Which? survey shows a 3-star owner satisfaction rating. Additionally, 1 in 10 owners say they definitely wouldn’t recommend the brand to anyone else.
  • Trustpilot indicates that 16% of customers rate the company 3 stars and lower.
  • Most issues related to these boilers include frequent breakdowns, poor customer service, and disputes over what is covered in the warranty.

Here’s what some customers have to say:

  • “It has been call out after call out for 3 years…The customer care department has no empathy or understanding.”
  • “Now had the boiler 7 years and have had 13 callouts in that time… The amount we’ve spent on repairs could’ve paid for a decent new boiler.”
  • “We have a Vokera Easi-Flo LE water heater, under four years old. The temperature is now dangerously erratic. We have had two heating engineers come to look at it who both said that in their opinion it should probably be junked as it is not repairable.”

Prices: Vokera is also one of the cheapest boilers on the market, with prices ranging from £550 to £850.

Warranty: Vokera boilers come with different warranty periods, depending on the model. Most Vokera boilers have a standard warranty of 2 years, but some models have a longer warranty of 5, 7, or 10 years.

4. Biasi

Biasi is an Italian company with experience in heating dating back to 1938. Biasi UK was formed in 1990.

Like Keston, Biasi is a smaller brand. Which? estimates that only 2% of people who own a gas boiler have a Biasi model.

So, why should you be sceptical about the brand? Let’s take a look:

  • Which? indicates a below-average customer satisfaction – 3 stars.
  • On Trustpilot, 25% of reviewers rate the company as 3 stars or less.
  • Common problems include no hot water, water pressure problems, irregular water heat, and sometimes complete failure of newer units.
  • A lack of customer care and bad after-sales service are also common gripes.

Complaints on Trustpilot include:

  • “Had a Biasi boiler fitted in 2 months ago only! It’s been going off ever since I purchased it! No hot water and no heating.”
  • “Had a fault with my parent’s combi boiler (Riva Plus HE 28C ERP) where there was hot water but no central heating. Classic Diverter valve failure. The guy on technical support was the most unhelpful person I’ve ever dealt with.”

Prices: Biasi boiler prices generally range from £500 to £1,000+

Warranty: Biasi boilers include a standard warranty of 2 years but, in some cases, an extended 7 years is available.

The Importance Of Investing In A Reliable Boiler

You may prefer an electric boiler to a gas boiler, or a combi boiler over a system boiler. Whatever the boiler type and size you’re looking for, you want to invest in a reliable brand. After all, a boiler is a 10 to 20-year investment (or longer). However, poor boiler choice can have some grim consequences, including:

  • A home without heat and hot water because the central heating isn’t working – again!
  • An appliance that malfunctions continuously brings a potential safety hazard into the home. Gas leaks, for example, can be fatal.
  • The worst boilers are inefficient. Bad boilers waste fuel while converting it to heat. This means bigger bills and higher carbon emissions.
  • “Buy cheap; buy twice” is advice worth heeding. Being stuck with an unreliable boiler from one of the worst boiler brands will cost you in repairs, call-outs, arranging alternative heating, and possibly investing in a new boiler altogether. So, weigh price carefully against quality. Paying an extra £500 for a reputable name could save you endless grief over the next 10 years.
  • Warranties on the poorer brands tend to be shorter than the best brands. If the boiler company offers you a 1-year warranty, know that it’s an indication of the quality you’re getting. It says the manufacturer isn’t prepared to stand behind their product. You ideally want a parts and labour warranty of 7 or even 10 years.

3 Boiler Brands With The Best Reputations

What boiler brand delivers quality and reliability you can depend on?

Here are three of our best boiler brands based on their consistent track record of great performance and solid support.

1. Worcester Bosch

Worcester Bosch is a UK-based company founded in 1962.

  • The Which? annual boiler survey reports a 5-star rating with over 90% of customers satisfied with their system.
  • On Trustpilot, 90% of reviewers rate Worcester Bosch boilers 4 or 5 stars.
  • Engineers and clients speak highly of the brand’s quality, efficiency, design, and back-up service. The boilers are often praised for how quiet they are. Additionally, Worcester Bosch boasts tons of industry awards.

Prices: Worcester Bosch prices range from £520 to £3,000+ (excluding installation costs)

Warranty: In many cases, you can get a Worcester Bosch warranty for 10 years; sometimes longer.

2. Viessmann

Viessmann is a German manufacturer founded over 100 years ago.

  • Which? points to an overall 84% satisfactory rating.
  • Trustpilot reviews are similarly strong, with 83% very favourable.
  • Viessmann boilers are praised for their excellent German engineering, great heating, quality components (no rubber or plastic), decent service plans, and readily available parts.

Prices: £900 to £3,000+

Warranty: The company offers extended warranties of up to 12 years.

3. Vaillant

Vaillant is a 150-year-old business started in Germany. Today, it is one of the largest heating companies in Europe, with a strong presence in the UK. Vaillant is a contender for the best boiler brand in the country; however, their products are more expensive.

  • Which? recognises Vaillant with 5 stars and an 88% customer satisfaction rating.
  • Trustpilot indicates almost 90% 4- and 5-star ratings.
  • Vaillant boilers are appreciated by clients and installers for their premium quality offering. The boilers are quiet and perform excellently. The extended warranties are backed up with prompt and professional expertise.

Prices: £1,400 to £4,000

Warranty: Extended warranties cover up to 10 years.


What boiler brand is the most reliable?

Viessmann, Alpha, Ideal, Vaillant, and Worcester Bosch boilers are regularly considered among the most reliable names in the UK.

How energy efficient is a good boiler?

New boilers in the UK must be A-rated. Modern efficiency ratings range from 80% to over 95%, depending on the type of boiler. A top-tier condensing boiler offers over 95% energy efficiency.

If I buy a cheap combi boiler, will it be good quality?

There are several combi boilers priced at under £1,000 – such as Alpha E-tec, Worcester Bosch Greenstar, and Ideal Logic – that offer great quality.


When purchasing a new boiler, it’s important to choose wisely. No matter what type of boiler you need, you want to avoid cheaper options that work out more expensive in the long run.

Don’t let price be your main consideration. Pay attention to reliability and workmanship, as well as the warranty and after-sales reputation. Contact Eco Happy for any boiler assistance you require.

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