Britain's most-fitted boiler
A Which? Recommended Brand for sixteen years running, by Worcester's own count, and a Royal Warrant holder. The boiler most heating engineers reach for when nobody is watching — and the one we fit more of than anything else.
Seven models across three Greenstar tiers, all fitted at a fixed price with no survey.
At a glance
The Greenstar line splits into three tiers and the differences between them are smaller than the price gap suggests. Here is the whole range before any detail.
Three tiers — the 2000, the 4000 and the 8000+ — plus one system boiler for homes keeping a cylinder. The 8000 Life this page used to list is discontinued; the 8000+ that replaced it starts at 32kW.
The spread from the smallest 2000 to the 36kW 8000+, every figure at a 35°C rise. Unusually for a range this size, no two of these give the same flow, so the number really is a way to choose between them.
On-site parts and labour with no call-out charge. Every term is conditional on a Greenstar System Filter, and the ten and twelve-year terms are only available through a Worcester Accredited Installer. We are one, we fit the filter, and we register it on the day.
Worcester's own published endorsements, in their own words — not ours. What they notably do not publish anywhere is where any individual Greenstar is built, so we do not say it either.
Both 4000 combis and the 4000 System share an identical cabinet, and the two 2000s are the same but 10mm shallower. The 8000+ is the exception: 780 x 440 x 365mm, taller and wider than everything else here.
Pairs with an unvented cylinder for mains-pressure hot water at every outlet at once, which is the one thing no combi on this page can do. 24kW is the largest 4000 System Worcester make.
Model by model
Each drawing is the real cabinet size from the manufacturer's own figures, against the same reference outline, so you can see at a glance which of these is actually bigger than the others.
A note on the kW number. On a combi, the kilowatt figure in the name is the hot water output — that is the industry convention and it is the bigger of the two numbers. The heating output, which is what actually feeds your radiators, is lower. Where the maker publishes both we have printed both. On a system boiler there is no hot water output at all, because the cylinder does that job, so the kW figure is the heating output.
The cheapest way into a Worcester Bosch. Same brand, same engineers, same seven-year warranty — a simpler control panel is most of what you give up.
Britain's most-fitted brand at close to value-brand money. If you want a Worcester and a sensible bill, this is the one.
The best-selling boiler in Britain, and the one we fit most. Colour display, quiet running, and a 10-year on-site parts-and-labour warranty.
The 30kW 4000 is the safe answer for most three and four-bed homes in our patch. If you are not sure, it is very hard to regret this one.
If you asked us to pick one boiler off this entire page without seeing your house, this would be it. It is the size that fits the most homes, in the tier that gets the balance right, from the make with the deepest parts network.
Worcester's flagship combi, and the start of the 8000+ range. Twelve years, a touch screen, and 13.7 litres a minute — genuinely more hot water than the 4000, not just a longer warranty.
The modulation range is the part worth paying for. A boiler that can turn itself down low enough to match a mild day runs steadily instead of firing hard and shutting off, and that is where the saving actually comes from. Note the size: the 8000+ is a taller and wider cabinet than the rest of the Greenstar range, so it is not always a straight swap into the space a 4000 came out of.
The biggest combi we recommend. 15.2 litres a minute is the most hot water any Worcester Bosch on this page will give you, which is what makes two bathrooms without a cylinder work.
The default system boiler for a two-bathroom house, and the largest 4000 System Worcester make. Pairs with an unvented cylinder for mains-pressure hot water everywhere at once.
This is the one to look at if you have two bathrooms and people who shower at the same time. A cylinder at mains pressure does not care how many taps are open; a combi always does. 24kW is the largest 4000 System Worcester make, which is what reheats a big cylinder quickly.
So which one? If you want a Worcester and the budget is firm, the Greenstar 2000 30kW gives you the brand and the parts network for the least money, at Worcester's seven-year guarantee rather than ten. If you are not sure, the 4000 30kW is the hardest one on this page to regret. The 8000+ 32kW is a genuine step up rather than a badge: twelve years, deeper modulation, and 13.7 litres a minute against the 4000's 12.3. Worcester's 8000+ combi range starts at 32kW — there is no 30kW and no 35kW in it — so 32 and 36 are the two real sizes, not rounded versions of the old ones.
Side by side
The same figures as the blocks above, in a form you can scan. Prices are for a straight swap in the same position, including VAT, flue, filter, flush, thermostat and taking the old one away.
| Model | Type | Hot water | Heating | l/min | Warranty | H x W x D | Fitted |
|---|---|---|---|---|---|---|---|
| Greenstar 2000 25kW | Combi | 25kW | 24kW | 10 | 7 yr | 724 x 400 x 300mm | £2,145 |
| Greenstar 2000 30kW | Combi | 30kW | 24kW | 12 | 7 yr | 724 x 400 x 300mm | £2,245 |
| Greenstar 4000 25kW | Combi | 25kW | 24kW | 10.2 | 10 yr | 724 x 400 x 310mm | £2,345 |
| Greenstar 4000 30kW | Combi | 30kW | 24kW | 12.3 | 10 yr | 724 x 400 x 310mm | £2,445 |
| Greenstar 8000+ 32kW | Combi | 32kW | 29.6kW | 13.7 | 12 yr | 780 x 440 x 365mm | £2,795 |
| Greenstar 8000+ 36kW | Combi | 36kW | 33.7kW | 15.2 | 12 yr | 780 x 440 x 365mm | £2,945 |
| Greenstar 4000 System 24kW | System | — | 24kW | — | 10 yr | 724 x 400 x 310mm | £2,395 |
Every figure in this table comes from pricing.json and was checked against Worcester Bosch's own published material on 19 August 2026 — their guarantee-length page, their product pages and their own gas and oil boiler product guide. Hot water flow rates are Worcester's published figures at a 35°C temperature rise, the basis used for industry comparison; Worcester also publish a lower "designed operational" figure at a 40°C rise. Guarantee lengths are conditional and the conditions are set out under each model: a Greenstar System Filter has to be fitted, the longest terms need a Worcester Accredited Installer, and the boiler has to be serviced every year. Prices include VAT at 20% and are for a straight swap in the same position.
Worcester Bosch has the best parts network in the country. If something fails on a Sunday in February, the part is on a van on Monday. That matters more than any specification sheet, and it is the single biggest reason a Worcester is an easy boiler to live with for fifteen years.
The Greenstar 2000 is the honest budget option — same parts network, simpler controls, and a seven-year guarantee rather than ten. The 4000 is the one most people should buy: a proper display, quieter running, and it modulates further down. The 8000+ is the flagship, with a twelve-year warranty, the widest modulation range and the most hot water of any Worcester here. It is also the biggest box on the page, and that is worth checking before you fall for it.
Seven years on the 2000, ten on the 4000, twelve on the 8000+ — on-site parts and labour, no call-out charge. Those are the accredited-installer terms, not the shelf terms: Worcester's standard guarantee is seven on the 4000 and eight on the 8000+, and the extra years need a Greenstar System Filter fitted by a Worcester Accredited Installer. We are one and we fit the filter as standard, so those are the terms you get. We also register it on the day so you never have to think about it. On a boiler you expect to keep for fifteen years, that is most of what you are buying.
You will read on plenty of installers' sites that every Worcester is built in Worcester. We used to say it on this page. Worcester Bosch themselves publish no such statement about any Greenstar boiler — they describe a manufacturing plant at Worcester, their history names a Clay Cross site in Derbyshire, and they never say which models come from where. So we have taken it off. What they do publish, in their own words, is a Which? Recommended Brand badge sixteen years running, a Royal Warrant, and Quiet Mark certification on much of the range. Their head office is in Worcester and that is the extent of what we can stand behind.
The kilowatt number on a combi is its hot water output, not its heating output, and that catches people out constantly. A 30kW combi does not put 30kW into your radiators. It is the reason a bigger badge number is not automatically a better match for your house, and why the sizing questions matter more than the model name.
Questions
It is a simpler one, not a worse-built one. Same maker and same parts network — but not the same guarantee: Worcester publish seven years on the 2000 and, for an accredited install with a Greenstar System Filter, ten on the 4000. What you give up is mostly the control panel — the 4000 has a colour display where the 2000 has a simpler one — and a little quietness.
If the budget is the constraint, we would rather put a 2000 in than talk you into a 4000 you have to stretch for.
More often than the old 8000 was. You get twelve years instead of ten, a touch screen, a wider modulation range that means less short cycling in a well-insulated house — and this time you also get more hot water, because the smallest 8000+ is 32kW and gives 13.7 litres a minute against the 30kW 4000's 12.3.
The thing to check is the wall. The 8000+ is 780mm tall and 440mm wide against the 4000's 724 x 400, so it is not always a straight swap into the same cupboard.
Worcester have discontinued it. Their own product page for the 8000 Life combi now redirects to a discontinued-products page, and it has gone from their site index. We took it off this page rather than keep selling a boiler its maker has stopped making.
The 8000+ is the replacement, and its outputs are genuinely different: 32, 36, 40, 45 and 50kW. There is no 30kW and no 35kW in the 8000+ combi range, so if you were looking at an 8000 Life 30 or 35, the honest nearest sizes are the 32 and the 36 — not the same boiler with a new badge.
Worcester publish nothing about how long spares stay available for a discontinued model. We have not been able to find a figure to quote you, so we are not quoting one.
Parts and labour, on site, with no call-out charge, for the full term. The terms Worcester publish are seven years on the Greenstar 2000, and on the 4000 and 8000+ a ladder rather than a single number.
On the Greenstar 4000 it is seven years as standard, eight with any Greenstar System Filter, and ten only when that filter is fitted by a Worcester Bosch Accredited Installer or Accredited Partner. On the 8000+ it is eight as standard, ten with the filter, and twelve on the same accredited basis. The Greenstar 2000 is seven years with a Worcester or third-party filter and there is no extended term on it at all.
We are a Worcester Accredited Installer and we fit a Greenstar System Filter on every Worcester we put in, so the ten and the twelve are the terms you actually get. Two things worth knowing: Worcester's smaller System Filter Micro does not qualify for any extension, and every term, from every manufacturer, depends on the boiler being serviced each year. That last one is the condition people most often fall foul of.
We register it on the day rather than leaving you a card and hoping.
They are the easiest of any brand we fit. Worcester Bosch is the most-fitted make in the country, which means merchant counters stock the common parts rather than ordering them in.
That is not a specification you will find on a brochure, and it is the single thing that most decides whether a breakdown is a day or a week.
Almost nobody needs to work that out themselves. The quote tool asks how many baths and separate showers you have and how many radiators, and sizes it from that.
The short version: one bathroom and up to about thirteen radiators is a 25 to 30kW; two bathrooms pushes you to 30 to 35kW; three or more bathrooms means a system boiler and a cylinder, not a combi.
Fifteen questions and we will size it, price it and tell you when we can fit it.
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