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Worst Boilers Guide


There is a multitude of boiler brands in the market, each offering several models and types of boilers. They are all competing for the same market and clients. Before spending money on a boiler, it’s important to find out which have the best track record and those that previous customers have had bad experiences with. It’s a quick process that will only take a few minutes but one that could save you money and a lot of heartache down the line.

What are the Worst Boiler Brands?

The boilers listed below have earned their tag from the reviews they have received from customers and engineers.


The Italian-based company with a presence in the UK has received poor reviews from multiple customers over the years. While the complaints vary, they can be classified and group. The most regular and persistent complaints have been:

  • The condensing boilers break down regularly and are not reliable.
  • The replacement parts for Ferroli boilers are not easy to find. Some customers have lamented going weeks without a working boiler.
  • Delivery of parts from the manufacturer is slow and unreliable.
  • For the available parts, the cost is exceptionally high.

Ferroli has an overall customer score of 2 out of 5 stars. In reliability tests, the oiler is rated 3 out of 5 stars, and the engineers rated the manufacturer at 1 out 5 stars. Most complaints about Ferroli revolve around the lack of parts.

What are the most common Ferroli boiler problems?

Some of the most common Ferroli boiler problems include:

  • Leaking – The shut valves on Ferroli boilers are not well-built and often lead to leaking inside the boiler. This is the most common problem installers are called to fix with most Ferroli boiler models.
  • Losing pressure – The expansion vessel inside the boiler needs to be repressurised occasionally because the boiler tends to lose pressure regularly.
  • Boiler locking out – This is often caused by a fault with the Printed Circuit Board (PCB). Replacing the PCB usually fixes the issue.

Vokera Boilers

Vokera is voted the second-worst boiler brand as of 2020. Over the years, the brand seems to have racked up a series of bad reviews and a bad reputation, particularly with their Vokera Vision 30C combi gas boiler.

Most of the complaints highlight various pitfalls with the boiler, which include:

  • Frequent breakdowns
  • Lack of parts and inaccessibility of the parts.
  • Short warranty, which shows a lack of confidence in their brand.
  • Hard to reach customer support.

On average, Vokera has a boiler warranty of 2 years. Most of the top-rated brands have between 5 to 10 years of warranty because of the superior component.

Customers rated the Vokera Vision 30C boiler a 3 out of 5, reliability tests scored the boiler at 2 out of 5 stars, and engineers rated the boiler 2 out of 5 stars.

Common problems with Vokera boilers

Some of the most common Vokera boiler problems include:

  • Lukewarm water – Vokera boilers have a problem with the diverter valve. After a diverter valve diagnosis, the most common problem is the valve getting stuck and preventing the water from heating adequately.
  • No water or heating – This problem happens in the winter because of frozen condensate because the pipe is not well insulated.
  • Boiler ‘puffing’ – The puffing sounds from your boiler are a result of the flue problem. In Vokera boilers, this is usually because the flue has come loose or is corroded. In most cases, the flue system needs to be replaced.

Worst Boiler In Efficiency

Efficiency is one of the most critical factors to consider when choosing a boiler. It relates to the total energy used by the boiler when providing heating. The more efficient the boiler, the more money it saves, and it also has a lower impact on the environment.

In 2018, new legislation meant that all new boilers should have an efficiency of at least 92%. That means that no matter what type of boiler you buy currently, you’re assured of having at least 92%. No matter what type or brand of boiler you buy, you’re assured of exceptional performance for the boiler, and there is very little difference between the boilers.

In terms of efficiency, it’s safe to say there are no worst boilers. Also, many homeowners don’t keep tabs on the performance of their boilers, and there haven’t been notable negative reviews given bases on the efficiency of the boilers with a similar rating.

Worst Boiler Warranty

The boiler warranty is one of the key features to look out for when considering which boiler you should buy. A warranty not only gives you peace of mind but also shows the brand’s confidence in its products.

As a general rule of thumb, the length of the warranty reflects on the quality of the boiler. However, while considering the length of the warranty, it’s also essential to check the level of support because this can vary from brand to brand. Customer reviews can give you a clear picture of the quality of customer support and get an idea of the experience that former clients had when their boiler broke down under warranty.

Currently, Worcester Bosch has one of the best warranties in the market. It is not only a ten-year warranty when the boiler is purchased through authorised dealers, But also a ten-year guarantee.

While brands like ATAG have a minimum warranty of 10 years, Others like Viessmann, Zanussi, Ferroli, Ideal, Baxi, Ariston and Alpha all have a minimum warranty of 2 or 3 years.

The brands with the shortest warranty are Main, Warmflow, and Biasi, which have a maximum warranty period of 5 years.

Warranty, Guarantee – What’s the Difference?

As you’re looking at the boiler’s warranty, you might come across an additional term ‘Guarantee.’ Boiler brands with a boiler guarantee exhibit extra faith in their products. A guarantee is basically an agreement with the brand. If the boiler breaks down within the guarantee period, they will come and repair or replace the boiler within a reasonable time.

Not all boiler brands offer a guarantee which makes a guarantee an excellent consideration when choosing the boiler brand to spend your money on.

As with warranties, the guarantee period varies. Worcester Bosch, Vaillant, and Glow-worm all offer guarantees, but the period varies. Glow-worm has the longest available guarantee at 15 years, followed by Worcester 12 years.

Worst Boilers By Price

Price is another factor to consider when buying a boiler. There is not the worst price per se because each boiler is designed for a specific market.

However, some brands might use the guise of making budget-friendly boilers by trading off quality and reliability. In general, you should be wary of low-quality boilers because you might have to buy another boiler in the not-so-distant future.

Although there aren’t boilers that are ranked as the worst in terms of price, the table below highlights the cheapest boiler from the leading heating brands in the UK:

Boiler Price Category
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

Vokera and Ferolli offer the cheapest boilers from the table above, while Viessmann, Vaillant and Worcester have the most expensive options.

Manufacturers with the best reputation and the highest reviews on Which? are more expensive. That indicates that in this case, it might be worth paying a little more for these boilers.

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