Worcester Bosch boilers reviewed: what that long guarantee actually requires

Worcester Bosch is the brand people ask us about by name more than any other, usually in the form of one question: is it worth the extra?

The honest answer is that the boiler itself is not the interesting part of the decision. Modern condensing boilers from any mainstream manufacturer are held to the same efficiency standard and fitted to the same regulations, and any of them installed properly will outlast a premium boiler installed badly. What you are really buying with Worcester is a long guarantee, a parts network your local merchant stocks, and an engineer base that knows the product well. All three are real.

The guarantee is also the part with the most conditions attached, and almost nobody reads them until the day they need to. So this is a review of the guarantee as much as the boiler, because that is where the value sits and where it gets lost.

The range, in plain terms

Worcester sell under the Greenstar name, and the numbers are tiers rather than sizes. Combi, system and regular versions exist across the range, so the model number tells you where in the range it sits, not what type of boiler it is.

• Greenstar 1000 and 2000. The entry tier. Perfectly sound boilers, shorter guarantees.
• Greenstar 4000. The mid tier, and the one that turns up on a lot of straightforward swaps.
• Greenstar CDi Compact and i System Compact. Built to fit where the full size units will not, which matters more than people expect in a kitchen wall unit.
• Greenstar Ri and Ri Compact, and the 8000 F floor standing. The regular and floor standing options, for houses that are keeping a cylinder or replacing a floor standing boiler.
• Greenstar 8000 and 8000+. The top tier, and the only one that reaches the twelve year headline.

The guarantee ladder

These are Worcester's own published guarantee lengths, and they are worth reading as three numbers per boiler rather than one.

• Greenstar 1000: five years as standard, fitted with a system filter, Worcester's own or a third party one.
• Greenstar 2000: seven years as standard, again with a system filter fitted.
• Greenstar 4000, CDi Compact, i System Compact, 8000 F, Ri and Ri Compact: seven years as standard, eight with any Greenstar System Filter, up to ten as an extended guarantee.
• Greenstar 8000+: eight years as standard, ten with any Greenstar System Filter, up to twelve as an extended guarantee.

Source: Worcester Bosch guarantee lengths

The figure at the top of each rung is not automatic. Worcester state that the extended length is achieved when the boiler is installed with any Greenstar System Filter by a Worcester Bosch Accredited Installer or Accredited Partner. An installer who is in the loyalty scheme without being accredited can still get you there, but has to make an additional payment to Bosch through their account to do it.

Which means the twelve year headline is a statement about your installer as much as about the boiler. If the guarantee is why you are choosing Worcester, the accreditation question is not optional.

The filter choice that cancels the extended guarantee

This is the detail worth the whole article. Worcester sell more than one filter, and the extended guarantee is tied to a Greenstar System Filter specifically.

Their terms state that extended guarantees are not available where the appliance is fitted with the System Filter Micro, and that the Micro carries the same guarantee duration as the boiler's standard term.

So two quotes can both say Worcester 8000+ with a Worcester filter, and one of them is a twelve year guarantee while the other is eight. Ask which filter, by name, and have it written on the quote.

Source: Worcester Bosch guarantee terms and conditions

The four conditions that decide whether you keep it

A guarantee is conditional, and Worcester's conditions are set out plainly. Non-compliance at any time may reduce, limit or invalidate it at their discretion.

• Registration within 30 days of installation. This is a condition, not a courtesy.
• An annual service by a competent, officially certified engineer, recorded in the service record and available for Worcester to inspect on request. A gap in the record is the usual reason a claim goes wrong.
• Correct installation and commissioning by a certified installer, to the manufacturer's instructions and the relevant standards.
• Somewhere the boiler can be safely reached. The terms require it to be in an easily and safely accessible area, with loft installations having a fixed loft ladder, boarding and lighting, and cupboard installations having the clearances given in the installation manual.

Worth noting alongside that: the guarantee does not include the cost or provision of the annual service. A long guarantee has an annual running cost attached to it, and that belongs in the comparison when you are weighing a twelve year boiler against a seven year one.

The start date most people get wrong

The guarantee runs from the date of installation, but only if the boiler is installed within six months of the date it was manufactured. If it has been sitting in a warehouse longer than that, the clock starts six months after manufacture instead.

That is a real consideration when a boiler comes off a clearance deal, has been in a merchant's yard a while, or has been in the back of a van since a cancelled job. It is entirely fair to ask what the manufacture date is on the unit being fitted to your wall.

One more: the guarantee period is not extended following a repair or replacement under it. Five years in, a replaced part does not buy you five more years.

What the guarantee does not cover

None of these exclusions are unusual, and most manufacturers exclude broadly similar things. They are worth reading because between them they describe exactly what protects a boiler.

• Damage caused by water quality, scale, sludge or blockages. This is precisely why the filter and a proper flush are not an upsell.
• External system components: radiators, pipework, wiring, pumps, third party filters and third party controls.
• Damage caused by system design, faulty installation, lack of maintenance or misuse.
• Jobs the manual makes yours, including re-pressurising the boiler, resetting it and thawing a frozen condensate pipe. If you call an engineer out in January to a frozen condensate, that is not a guarantee visit.

Source: Worcester Bosch guarantee terms and conditions

Where Worcester is not the obvious answer

Two situations, and an installer who says otherwise is selling rather than advising.

The first is where nobody near you fits them regularly. Parts availability and engineer familiarity are worth more on a cold Sunday than any spec sheet, and there are areas where a different mainstream brand is the one every local van carries.

The second is a genuinely tight space. Cupboard clearances are a real constraint, and the compact models exist because the full size ones do not fit everywhere. If your boiler lives in a kitchen wall unit, the fit is a question to settle at survey rather than on the day.

And if the longest guarantee is the whole reason for the choice, keep in mind what it costs to keep alive: a documented service every year for the full term. A twelve year guarantee that stops being serviced in year four is a four year guarantee.

What to ask before you sign

Five questions. Ask every installer the same five and the quotes become comparable.

• Which model exactly, and which filter exactly, by name?
• Are you a Worcester Bosch Accredited Installer or Accredited Partner, and what guarantee length will actually be registered against my boiler?
• Are you registering the boiler, or am I, and by when?
• What is the manufacture date on the unit you are fitting?
• Is the system being flushed, and is that included?

The short version

Worcester make good boilers, and the guarantee is the strongest reason to pay for one. It is also conditional in four specific ways, tied to a specific filter, and shorter than the headline unless your installer is accredited.

Get the model, the filter and the registered guarantee length written on the quote, then compare it against the other quotes on the same basis. We can arrange quotes from Gas Safe registered installers covering Northampton and Milton Keynes if you want to see it priced properly.