Common mistakes that can invalidate your boiler warranty

In the depths of winter, not only could forgetting your annual boiler service lead to days without heating, but it could also make for an expensive bill for fixing faults that you thought would be covered under warranty.

Manufacturer warranties lasting at least a few years are typically included when you buy a new boiler, and should cover the cost of repairs if yours breaks down or develops a fault, letting you rest easy for the first few years of a boiler's life.

But fail to stick closely to the warranty terms and conditions and you could find yourself unexpectedly out of pocket. Read on to discover the potential pitfalls to avoid, and how to make sure you stick to your boiler warranty's terms and conditions.

Minimise the risk of your boiler breaking by installing one from a reliable brand in the first place. Read our guide to the best boiler brands to find out which one last the longest.

How to avoid falling foul of boiler warranty exclusions

The specific terms and conditions you need to stick to will vary by warranty, so it's worth reading the small print carefully. But avoiding these three common mistakes will stand you in good stead, as they are common across most boiler warranties.

1. Mistake 1: Not using a Gas Safe engineer to install the boiler. Unless stated otherwise, this doesn't have to be one of the manufacturer's engineers, but it's vital they are on the Gas Safe Register.
2. Mistake 2: Failing to register the warranty with the manufacturer within 30 days of the installation. This doesn't happen automatically - you have to 'activate' the warranty within 30 days to be covered. You can usually do this on the manufacturer's website, or by calling them.
3. Mistake 3: Forgetting to get your boiler serviced annually. If your boiler hasn't been properly and regularly serviced, the manufacturer may argue that you haven't taken appropriate steps to minimise the risk of problems, and refuse to pay out. Make sure the service is carried out by a Gas Safe engineer, and that they give you a certificate afterwards, as evidence that your boiler has been serviced.

Find a gas engineer near you that's on the Gas Safe Register and has been assessed and vetted by Which? Trusted Traders.

What is a boiler warranty?

When installing a new boiler, you typically get a manufacturer warranty on it that covers the cost of repair for at least some boiler problems - provided you adhere to the T&Cs.

Gas boiler warranties usually last several years, with some manufacturers offering warranties that last for 10 years or more.

Oil boilers tend to have shorter warranties, and electric boilers typically offer warranties for only two or three years. This doesn't mean that they're more likely to break down in this period, but that the manufacturer won't necessarily investigate the fault after this time.

What to check in your boiler warranty

Not all warranties are created equal. If you value extra peace of mind, then the quality of the manufacturer's warranty is something you may want to consider when buying a new boiler.

Our Which? Recommended boiler brands offer warranties ranging from two to twelve years. They cover the costs of both parts and labour for any repairs covered by their warranties.

When looking at boiler warranties it is worth checking the following:

• How long the warranty is - boilers tend to be pretty reliable in their first few years of life, but the longer the warranty, the longer you'll have the reassurance in place that any faults that do crop up are likely to be covered.
• Which parts are covered- sometimes 'consumable parts' (parts that are expected to need replacing in time) such as fuses and filters aren't covered.
• If both parts and labour costs are covered - most warranties cover the cost of parts, but some may not cover labour costs to carry out repairs. Others will take a deposit for any call out that is only returned if it's confirmed that the fault is covered by the warranty.
• Exclusions that could invalidate the warranty- almost all warranties will have the exclusions that we outlined earlier, but check there aren't any extra ones in the T&Cs.

If your boiler warranty has expired, read our guide on boiler repair costs to make sure you are not being charged over the odds to fix common faults.

The benefits of an annual service

In a recent Which? survey of boiler owners, half of them told us that they don't get their boiler serviced annually. We suspect this is often an unintentional oversight amidst the volume of life admin, but regardless of the reason, if you don't get your boiler serviced each year it could mean you're invalidating any warranty you have.

Regardless of whether your boiler is still under warranty, it's a good idea to get it serviced annually to minimise the risk of it conking out and identify unavoidable faults early. Prevention is always better (and usually cheaper) than cure, and nobody wants to be without heat or hot water for even a day or two in winter.

A one-off boiler service costs £79 on average, according to our survey of 10,064 homeowners in June 2025. People without boiler cover paid on average £156 for repairs if their boiler needed them.

Our guide on getting the best boiler service has more detail on typical costs and what to expect from your annual service.

Get boiler service reminders with the Benchmark App

Remembering to get your boiler serviced can be a pain but the Benchmark app (available on iOS and Android, or via the web) can make staying on top of boiler servicing that bit easier.

If your boiler has been recently installed, and the installer created a Digital Benchmark record (they should have told you if they did so), downloading the digital Benchmark app acts as a digital record of your boiler's installation and servicing history.

It also sends push notifications to alert you when it's time to get your boiler serviced, making it easier to keep up with regular servicing and ensuring you keep your boiler warranty valid.

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* In June 2025, we surveyed 7,000 gas boiler owners about their experiences of owning and using a boiler.