Baxi boilers reviewed: what the warranty actually says
Baxi's warranty ladder is the simplest of the big brands: the range name tells you the years. But the 800's filter condition carries the harshest penalty we have found anywhere, and the small print still has jobs on your side of it.
21 August 2026 · 5 min read
This is the fourth of our brand reviews, and like the Worcester Bosch, Vaillant and Ideal pages it is not a review of whether the boilers are any good. Baxi have been making boilers in Britain for over a century, installers fit them everywhere, and parts are not hard to find. What actually differs between two quotes is the guarantee behind the appliance, so as before we have read Baxi's own published warranty information rather than anyone's opinion of it.
The headline finding is that Baxi run the simplest warranty ladder of the four brands we have covered. The range number tells you the years, and unlike the other three, the length does not depend on which loyalty scheme your installer belongs to. But simplicity is not the same as softness, and one condition on the flagship range carries the harshest penalty we have found in any manufacturer's terms so far.
The ladder, as Baxi publish it
Baxi publish the warranty per range, all parts and labour, and all subject to the same three conditions: registration within 30 days of installation, the Benchmark checklist completed by the installer, and an annual service.
- Baxi 800 range: 10 years, with a catch on the filter covered below.
- Baxi 600 range: 7 years.
- Baxi 400 range: 5 years.
- Baxi 200 range: 2 years.
What makes Baxi different from the other three
Worcester's longest guarantee needs an accredited installer and the right filter. Vaillant's depends on the installer's tier in their loyalty scheme. Ideal's flagship needs a MAX accredited installer. Baxi's ladder has none of that: the 800 is a 10 year boiler whoever fits it, provided the admin gets done. For a homeowner comparing quotes, that removes a whole category of question. You do not need to ask which scheme your installer belongs to, only which range is on the quote.
That matters when you are comparing like with like. Two quotes for a Baxi 800 should carry the same cover. Two quotes for a Worcester or a Vaillant can differ by years of guarantee depending on who is fitting it, which is easy to miss when the model number on both quotes is identical.
The filter condition: ten years or two
Here is the catch. On the 800 range, the magnetic filter supplied with the boiler must be fitted, and maintained, for the length of the warranty. If it is not, the warranty does not shorten by a couple of years. It reverts to two.
That is the sharpest single condition we have found in any of these reviews. Worcester decline to offer their extended guarantee with the wrong filter fitted. Vaillant use their filter to add years to the standard term. Baxi take eight years away. And note the word maintained: Baxi's own servicing guidance says the annual service should include checking that the system water is clean and cleaning the magnetic filter. A filter that was fitted on day one and never opened since is a condition half met, and the service records are the evidence of the other half.
If you are quoted an 800, the filter should be on the quote, and cleaning it should be part of every service. Neither is optional if the 10 year figure is the reason you chose the boiler.
The three conditions, and what missing one costs
Baxi's terms are blunt about the downside. If the warranty is not registered within 30 days of installation, or the Benchmark checklist is not completed by the installer, or the annual service is missed, the warranty reverts to the standard one year. Not to some middle figure: to one year, on a boiler that may have been sold to you on the strength of ten.
The Benchmark paperwork keeps earning its place in these reviews. It is a condition at Worcester, at Vaillant, at Ideal and here. If you take one thing from this series, it is that the commissioning checklist your installer fills in on the day is worth more than the box the boiler came in. Our paperwork guide covers what it is and who should have completed what.
What the warranty covers, and the sludge line
Baxi's published position is that the warranty covers the boiler and its integrated controls. If the boiler fails because of something external, and their examples are incorrect installation and sludge in the system, that is not covered, and a charge will be incurred for replacing the damaged or blocked components.
Every brand we have reviewed excludes sludge damage one way or another, and it is the exclusion that actually gets used, because dirty system water is the most common killer of modern heat exchangers. The water around Northampton and Milton Keynes is hard, which adds scale to the same problem. A proper flush and inhibitor at installation is what protects you here, whichever name is on the boiler.
One genuine positive to weigh against it: Baxi state plainly that the warranty is transferable. If you move house, the cover stays with the boiler, as long as it was registered and the new owner keeps up the annual service. If you are buying a house with a youngish Baxi on the wall, asking the seller for the service records is worth the awkward email.
One label, several brands
A local wrinkle worth knowing: Baxi Heating UK is also the company behind Main and Potterton, among others. The Main Eco combis fitted in volume into rental and budget installations, and the Potterton boilers in plenty of older systems, come from the same stable. The warranty behind each label and model is its own, so do not read the Baxi ladder above across onto a Main or a Potterton. If your quote names one of the sister brands, ask for the warranty length in writing for that exact model.
What to ask if you are quoted a Baxi
Which range, since 800, 600, 400 and 200 carry four different terms. Is the filter included on an 800 quote, and will cleaning it be part of the annual service. Who registers the warranty, and will it be done inside 30 days. And will the system be flushed and inhibited, given what the exclusions say about sludge.
If you would like quotes from installers we have already vetted, tell us about the job and we will put three of them in touch. They will answer all four questions without needing to look anything up.