Guarantee Vs Warranty & Which Manufacturer Is The Best

09 May. 2019

Written by Neil Marsh MCIPHE RP RHP EngTech

Which boiler manufacturer currently offers the most comprehensive boiler guarantee or warranty, and what is the difference between the two?…

It is a confusing question for many people, and without understanding legal wording, the language of the trade and having inside knowledge, discerning which boiler manufacture offers the best protection currently on new boilers is difficult for the layman to comprehend.  

Below we have broken down key points of the main boiler manufacturers terms of cover and our thoughts on who delivers the best after-sales/boiler warranty/guarantee support. 

What is the difference between a guarantee and a warranty?

A boiler guarantee is a contract between the homeowner and the boiler manufacturer. Under a boiler guarantee, the boiler manufacturer is to attend your property and repair or replace the boiler within a reasonable period of time without quibble. It is legally binding and improves your consumer rights.

A boiler warranty is similar to an insurance policy. The boiler manufacturer promises to come and have a look at the problem. However, warranties allow manufacturers to charge for call-outs and the terms and conditions of a warranty can be changed without notice.


All of the manufacturers have terms and conditions that must be met for them to honour any warranty or guarantee they supply. Here are key points that you must follow to ensure any current boiler guarantee/warranty remains valid:

  • ​Ensure the Benchmark is completed in full and is to hand
  • Ensure the boiler is registered within 30 days of installation
  • Ensure there is safe access to the boiler 
  • Some extended warranties /guarantees will require you may have to use an “Approved Installer”. Check your boiler installer is approved where necessary and how long of a warranty you will get
  • Have the boiler serviced annually and keep the documentation to hand and fill out any log books
  • Ensure when having a new boiler installed onto an old system it is power flushed
  • Ensure any faults you contact the manufacturer about are not user related, such as low pressure or an interruption in the gas supply

Worcester & Hereford boiler installations, as well as all others we do throughout the region, are done to a high standard, and we ensure that any warranties or guarantees from the manufacturer will not be invalidated due to shoddy workmanship. 

Sadly, it is common for “installation defects” and failure to power flush existing central heating systems, or flush new ones correctly, to invalidate aspects of the boiler manufacturers cover. Most installers do not power flush central heating systems or stress the importance of it, and many fail to install boilers correctly.  We undertake power flushes as standard and offer power flushing in Worcester, Hereford and the areas we work into any client that has related problems. You would be amazed how many central heating systems we do! 

Baxi Warranty

Baxi’s terms and conditions are standard, and they give a flexible 60 days either side of the boilers installation date to get the boiler serviced. You may be asked to pay a deposit before an engineer attends. This will not be refunded if the fault is non-boiler related.  

Baxi currently offers warranties of up to 10 years and do not require installers to be approved; extended warranties are available to all installers. They are often the best value for money in our opinion.

In our experience, Baxi, second to Worcester Bosch have the best average response times. Along with Worcester Bosch they also are the fairest at dealing with customers and are concerned about their “brand image”. Baxi employs a considerable team of in-house engineers for their warranty cover, all of whom have very well stocked vehicles. 

Ideal Boilers Warranty

Ideals terms and conditions are standard. They have a strict servicing policy and the boiler must be serviced every 12 months. You will likely be asked to pay a deposit before an engineer attends and you will not be refunded for a non-boiler fault, or if documentation is not complete and available on site. You will likely be charged if the fault is considered an exclusion such as sludge related or an installation defect. 

Ideal currently offers up to 10 years warranty on their boilers and do not require installers to be approved. They have some good value products at present. 

In our experience, behind Ideal fall being Baxi in response times and are less tolerant of defects from the installation process. 

For all unbiased boiler quotes in Hereford & Worcester, including the areas around, contact us. We will advise you on what the best make and model is for your situation. 

Vaillant Guarantee

Vaillant’s terms conditions are standard. Vaillant boilers must be fitted by a Vaillant Advanced Installer to receive an extended Guarantee, otherwise, the minimum standard warranty applies.  You will likely be asked to pay a deposit before an engineer attends and you will not be refunded for a non-boiler fault.

Ideal currently offers up to 10 years warranty on their boilers, with a 2-5 years as standard for non-approved installers.  

In our experience, they are no long reputable enough for us to fit their products. We have seen far too many incidents where boiler repairs under Guarantee are being refused by their engineers where we have seen no valid reason for them to deny such work. Their response times vary, but they do have their own in-house team with well-stocked vehicles. 

We advise people to look at their Trust Pilot complaints and you will see that aftersales and guarantee work complaints are a common occurrence. 

Worcester Bosch Guarantee

Standard conditions apply. The boiler must be fitted by a Worcester Accredited Installer to receive an extended warranty. They also may charge for non-boiler related faults and standard conditions not being met, including documentation not on site. Worcester will extend the terms of the Guarantee to other qualifying products, when installed at the same time as the new boiler, such as the WAVE, Comfort controls and Greenstar Filters.

Worcester offers 5-7 year warranties as standard with up to 10 years for their approved installers. Their products are generally more expensive than most.

In our opinion, Worcester Bosch has the best average response times, are the fairest at dealing with customers and are concerned about their “brand image” they employ a considerable team of in-house engineers for their warranty cover, who are well prepared. Although they are market leading in service, they typically are more expensive, and in our opinion, there are much better built and better value products out there for nearly all of their boiler types. 

Viessmann Guarantee

Standard conditions apply. The boiler must be fitted by a “Viessmann Registered Installer” to receive an extended warranty. They also may charge for non-boiler related faults and standard conditions not being met. 

Viessmann offers 3-year warranties as standard with up to 10 years for their registered installers. They have good value products.

Viessmann is a growing company that make some fantastic products that are well engineered. They currently one of the less common brands in the UK, but are growing. They are a leading provider of gas boilers in Germany. 

In recent years Viessmann has been growing their in-house team of engineers for warranty related work, of which mostly covers any warranty related work. They have also significantly improved part availability in the last number of years, of which has been a problem in the past. 

As Viessman boilers are not as common at present, we do not have the experience with their aftersales/warranty as we do with the other companies. However, we would say all the dealings we have had with them to date have been nothing short of professional and high-quality. 

If you are looking for boiler quotes in Hereford, Worcester and the surrounding areas, we can provide you quotes on all leading boiler manufacturers. We will give you the best advice on what the boiler make and model is right for your situation and give you all the essential information, although ultimately the decision is yours.