Who are Worcester Bosch?
Worcester Bosch is the trading name of Bosch Thermotechnology Ltd, the UK heating arm of the German Bosch Group. The business began in 1962 as Worcester Engineering, founded by Cecil Duckworth in the city of Worcester, and made its name in the 1970s and 1980s as one of the pioneers of the combination boiler in Britain. It moved to its current Warndon headquarters and factory in 1990 and became part of the Bosch Group in the 1990s.
Gas boilers for the UK market are still assembled at Worcester, with a second site at Clay Cross in Derbyshire. The company states that it holds a Royal Warrant for supplying boilers to the Sandringham Estate and that the Greenstar range has repeatedly been named a Which? Best Buy; both are the manufacturer's own claims.
For a homeowner the point is scale: almost every Gas Safe engineer knows the products, parts are stocked by every merchant, and the manufacturer runs its own nationwide service team. You also pay a little more than for an equivalent Ideal or Baxi.
Our hub on the best combi boilers in the UK puts the Greenstar range alongside its rivals; this review looks at the brand on its own.
Which Worcester Bosch ranges can you buy today?
Every current Worcester Bosch gas boiler carries the Greenstar name, followed by a number that tells you where it sits in the line-up. The higher the number, the longer the guarantee and the more features. The table uses manufacturer figures; flow rates are at a 35°C rise unless stated.
| Range | Type | Outputs | Hot water flow | Guarantee (manufacturer terms) |
|---|---|---|---|---|
| Greenstar 1000 | Combi | 24, 30 kW | about 10.8-12 l/min | 5 years when fitted with any system filter; extended terms via Worcester Accredited Installers |
| Greenstar 2000 | Combi | 25, 30 kW | 9 / 10.8 l/min at 40°C rise | extended terms up to 10 years subject to a system filter and accredited installer |
| Greenstar 4000 | Combi and system | Combi 25, 30 kW; system 12-24 kW | 10.2 / 12.3 l/min | 7 years standard, 8 with a Greenstar filter, up to 10 via accredited installer |
| Greenstar 8000 Life | Combi, system and regular | Combi 30, 35, 40, 45, 50 kW; system and regular 30-50 kW | 10.7-17.9 l/min at 40°C rise | 8 years standard, 10 with a filter, up to 12 via accredited installer or FastTrack |
| Greenstar 8000 Style | Combi and system | 30, 35, 40, 45, 50 kW | as 8000 Life | as 8000 Life; black or white fascia |
| Greenstar CDi Compact | Combi | 28, 32, 36 kW | about 11-14 l/min | up to 10 years via accredited installer |
| Greenstar Ri | Regular (heat-only) | 12, 15, 18, 21, 24, 27, 30 kW | n/a | 5-7 years standard, longer via accredited installer |
The Greenstar i (25i and 30i) and CDi Classic combis that dominated the 2010s have been superseded by the 4000 and 8000 respectively, but they remain fully supported and spares are plentiful. The detailed comparison of the two current best-sellers is in our Greenstar 4000 vs 8000 review, and the system boiler versions are covered in what a system boiler is and who it suits.
Guarantee terms change with promotions and installer status, so always ask the installer to confirm the exact number of years in writing before you accept a quote.
What are the documented strengths of a Worcester Bosch boiler?
- Guarantee length. Up to 10 years on the 4000 and up to 12 years on the 8000 Life and Style through Worcester Accredited Installers, parts and labour, provided a system filter is fitted and the boiler is serviced annually.
- Installer and spares network. The largest of any UK brand. A Worcester Bosch engineer or an independent with the parts in the van can usually attend within days, and the manufacturer's own service team covers guarantee call-outs.
- Controls. The Greenstar 4000 and 8000 integrate with the Bosch EasyControl smart thermostat and with Worcester's wired and wireless programmable controls, including weather compensation. Older models use the plug-in MT10 mechanical timer or the digital DT10RF.
- Compact budget models. The Greenstar 2000 and 4000 are designed to fit a standard 300 mm deep kitchen cupboard, and the 2000 is the cheapest Worcester model that still works with the brand's RF wireless controls.
- Hydrogen blend readiness. Current Greenstar boilers are certified to run on a 20 per cent hydrogen blend, in line with the rest of the industry.
- Documentation. User guides, installation manuals and fault code explanations are freely available on the Worcester Bosch website; see where to find boiler manuals if you have lost yours.
What are the weaknesses and common complaints?
Being honest about the limits is more useful than another five-star summary.
- Price. Like-for-like, a Greenstar typically costs £200-£500 more fitted than an Ideal Logic Max or Baxi 800 with the same 10-year guarantee.
- Aluminium heat exchangers. Most Greenstar models use an aluminium-silicon heat exchanger rather than stainless steel. Aluminium transfers heat well but is less tolerant of poor water quality, which is why the filter is a guarantee condition.
- Flow rate honesty. The 1000 and 2000 are 24-30 kW on paper but deliver 9-12 l/min of hot water; a household with two showers will outgrow them.
- Guarantee small print. The headline 10 or 12 years applies only through accredited installers with a filter and annual service; through a non-accredited installer the 4000 drops to 7 years and the 8000 Life to 8.
Common owner issues are those shared by every modern combi: pressure loss from a weeping PRV or expansion vessel, hot water that goes cold intermittently when the diverter valve or flow sensor sticks, and frozen condensate pipes in a cold snap. Our page on Worcester Bosch fault codes covers the symptoms code by code.
Who does a Worcester Bosch combi boiler suit?
| Situation | Recommended range | Why |
|---|---|---|
| Flat or small terrace, one bathroom, tight budget | Greenstar 1000 or 2000 (24-25 kW) | Lowest price with full brand support; fits a cupboard |
| Three-bedroom house, one bathroom | Greenstar 4000 30 kW | 12.3 l/min, 10-year guarantee, EasyControl-ready |
| Three or four bedrooms, bathroom plus en suite | Greenstar 8000 Life 35 or 40 kW | 12.5-14.3 l/min at a 40°C rise; 12-year guarantee |
| Large detached, two or three bathrooms | Greenstar 8000 Life 45 or 50 kW combi, or a 4000/8000 system boiler with a cylinder | Only the biggest combis manage two showers; a cylinder is usually better |
| Kitchen on show, want a designer finish | Greenstar 8000 Style in black | Same engineering as the Life with a glass-fronted fascia |
| Replacing a regular boiler and keeping the tanks | Greenstar Ri or 8000 Life regular | Straight swap without replumbing |
Unsure of the output? Use our boiler size calculator rather than copying the number on the old boiler.
How much is a new Worcester Bosch boiler?
Prices below are typical ranges for 2026 across national installers and merchants. Boiler-only prices exclude flue, filter, controls and installation; fitted prices assume a like-for-like combi swap in the same position.
| Range | Boiler only (typical) | Fitted, like-for-like swap |
|---|---|---|
| Greenstar 1000 | £850-£1,100 | £2,000-£2,600 |
| Greenstar 2000 | £900-£1,200 | £2,100-£2,800 |
| Greenstar 4000 combi | £1,100-£1,500 | £2,300-£3,300 |
| Greenstar 8000 Life combi 30-35 kW | £1,400-£1,800 | £2,800-£3,800 |
| Greenstar 8000 Life combi 40-50 kW | £1,700-£2,100 | £3,200-£4,500+ |
| Greenstar 4000 or 8000 system boiler (excluding cylinder) | £1,000-£1,700 | £2,200-£3,600 |
What moves the price: output, whether the flue needs rerouting or extending, a gas pipe upgrade to 22 mm, a powerflush (£300-£800), smart controls (£120-£250 fitted) and your region. Converting from a regular boiler to a combi adds £500-£1,500 for pipework and tank removal. The full brand-by-brand picture is in our guide to boiler prices by brand, and what a new boiler costs in the UK explains every line of a quote.
Which fault codes do Worcester boilers show?
Greenstar boilers display either a short letter-number code (older Greenstar i, Si and CDi models) or a longer numeric code with a text message (Greenstar 2000, 4000 and 8000). The meanings below are summarised from Worcester Bosch user and installation manuals; the code on a newer display often pairs with a three- or four-digit cause code such as 224 or 227.
| Code | Meaning in brief | What you can safely do |
|---|---|---|
| EA 227 | No flame detected on ignition | Check other gas appliances work and the condensate pipe is not frozen; reset once |
| EA 229 | Flame lost during operation | As above; if it repeats, call an engineer |
| E9 219 / E9 224 | Safety or high-limit temperature sensor has tripped (overheating) | Do not keep resetting; book an engineer |
| A1 281 | Pump stuck or running dry | Check pressure is 1-1.5 bar; top up, then reset once |
| C6 215 / C7 214 | Fan speed fault or fan not running | Engineer |
| CE 207 / H07 / LoPr message | System pressure too low | Top up via the filling loop or key to 1-1.5 bar |
| A21 | Wireless control has lost communication with the boiler | Check thermostat batteries and range; re-pair |
| 1017 and similar 1xxx codes | Low water pressure on newer Greenstar displays | Top up and reset once; investigate repeated loss |
| 1021, 1101, 2951 | Sensor and PCB-related cause codes on 4000/8000 displays | Note the code and call an engineer |
A single reset after fixing the obvious cause is reasonable; repeated resets are not. How to reset a boiler shows the button and the sequence on each Greenstar generation, and Worcester Bosch boiler pressure explains the filling loop and the white plastic filling key used on CDi Compact and i Junior models.
What do the Worcester boiler symbols and settings mean?
Owners search for the same handful of control questions, so here they are in one place.
- Settings 1 to 6. Older Greenstar i and CDi boilers have a central heating temperature dial marked 1 to 6 rather than in degrees. Roughly, 3 to 4 gives a radiator flow temperature in the 60s, which is efficient and comfortable for most homes; 6 is the maximum of around 80°C. The hot water dial has a separate scale with an "E" position for eco pre-heat.
- Eco mode. Turns off hot water pre-heat so the boiler uses less gas when idle; comfort mode keeps the heat exchanger warm for faster hot water.
- Air purge mode. When a Greenstar is first powered up or after certain faults it runs the pump in short bursts for several minutes to clear air. The display may show a purge symbol or a pump icon; this is normal and finishes on its own.
- Turning the heating on or off. On a 4000 or 8000, select the radiator symbol on the touch controls and choose a temperature, or use the room thermostat or app. On dial models, turn the heating dial from off to the desired setting and check the room thermostat is calling for heat. To switch the boiler off entirely use the power button or the fused spur.
- Display symbols. A radiator means heating demand, a tap hot water demand, a flame a lit burner, a spanner a service due, and a padlock or key icon on newer models a locked display.
- MT10 and other timers. The MT10 is a mechanical plug-in timer for older Greenstar fascias; the DT10RF, DT20RF and Bosch EasyControl are the digital and wireless options, explained in boiler thermostats and controls explained.
How old is my Worcester boiler?
The serial number on the data badge (inside the drop-down flap or on a label under the boiler) is the definitive answer: Worcester Bosch customer service can decode the production date from it. If you only have the model name, this chart gives an approximate age; launch years overlapped.
| Model name on the casing | Approximate production years |
|---|---|
| Greenstar 8000 Life, 8000 Style, 4000, 2000 | 2019-2020 onwards (current) |
| Greenstar 1000 | around 2021 onwards (current) |
| Greenstar CDi Compact, Si Compact | 2013 onwards |
| Greenstar i (25i, 30i) and i System | around 2011-2021 |
| Greenstar CDi Classic (28, 34, 38, 42CDi) | around 2010-2020 |
| Greenstar i Junior (24i, 28i Junior) | around 2005-2012 |
| Greenstar Highflow CDi, FS CDi | 2000s-2010s |
| Worcester 24i, 28i, 24CDi, 28CDi, 35CDi II (non-condensing) | late 1990s-mid 2000s |
| Worcester Highflow 400, 240, 280, 350 | 1990s |
Any boiler in the bottom three rows is non-condensing, well past its design life and usually running at 65-78 per cent efficiency. Our guide to how long boilers last helps you decide when a repair stops making sense.
Worcester Bosch vs Vaillant and Baxi: how do they compare?
| Criterion | Worcester Bosch | Vaillant | Baxi |
|---|---|---|---|
| Mid-range combi | Greenstar 4000 (25-30 kW) | ecoTEC plus (26-40 kW) | Baxi 800 Combi 2 (24-36 kW) |
| Mid-range guarantee | 7 years, up to 10 via accredited installer | 5 years, up to 10 via registered installer with protection kit | 10 years with registered filter |
| Heat exchanger | Aluminium-silicon on most models | Stainless steel on ecoTEC ranges, aluminium on ecoFIT pure | Aluminium |
| Typical fitted price, 30 kW class | £2,300-£3,300 | £2,400-£3,800 | £1,900-£3,000 |
| UK manufacturing | Worcester | Belper, Derbyshire | Preston, Lancashire |
| Where it wins | Spares, installer familiarity, controls ecosystem | Modulation, quiet running, heat exchanger material | Price for a 10-year guarantee |
None of the three is a wrong answer. The Vaillant boilers review and Baxi boilers review go through the rivals in the same depth as this page, and the UK boiler brands comparison covers who owns whom.
How do you register a Worcester boiler or contact Worcester Bosch?
Registration is normally done by the installer through the Worcester Bosch professional portal within 30 days of commissioning, and you should receive written confirmation of the guarantee length. If nothing arrives within a few weeks, ask the installer for the reference or contact Worcester Bosch with your serial number. Keep the Benchmark checklist and every service record together, because the guarantee depends on them.
Worcester Bosch general enquiries are on 0330 123 9559 and technical support on 0330 123 3366; opening hours are published on the website. For anything involving gas, the flue or the casing you still need a Gas Safe registered engineer, whether the manufacturer's own team or an independent you have checked on the register.
Frequently asked questions
How long should a Worcester Bosch boiler last?
A Greenstar boiler that is serviced every year and protected by a magnetic filter and inhibitor typically runs for 12-15 years, and many older Greenstar i and CDi models are still working beyond that. The guarantee of up to 10 or 12 years on current ranges gives a good indication of the design life the manufacturer is comfortable standing behind. Poor water quality and skipped services shorten it considerably.
How much is a new Worcester Bosch combi boiler fitted?
In 2026 a straightforward like-for-like swap typically costs £2,000-£2,800 for a Greenstar 1000 or 2000, £2,300-£3,300 for a Greenstar 4000 and £2,800-£4,500 or more for a Greenstar 8000 Life or Style, depending on output, flue, controls and region. Boiler-only prices from merchants run from roughly £850 for a 1000 to around £2,000 for a 50 kW 8000 Life.
What does the A21 fault mean on a Worcester boiler?
On Greenstar boilers fitted with a Worcester Bosch wireless control, A21 indicates that the boiler has lost communication with the room thermostat or its receiver. Check the thermostat batteries and that it has not been moved out of range, then re-pair it following the control's instructions. If the code returns, the receiver or control may need replacing by an engineer; the boiler itself is usually healthy.
What is eco mode on a Worcester combi boiler?
Eco mode switches off the pre-heat function that keeps a small amount of water warm inside the boiler so hot water arrives at the tap faster. With eco selected the boiler uses less gas while idle, but you wait a few seconds longer for hot water and may notice a brief cold slug. Comfort mode keeps pre-heat on. Most households choose eco in summer and comfort in winter.
How do I register a Worcester Bosch boiler for the guarantee?
The installer should register the boiler through the Worcester Bosch professional portal within 30 days of commissioning, and you receive confirmation by email or post. If you have not heard anything, ask the installer for the registration reference or contact Worcester Bosch customer service with the serial number from the data badge. Unregistered boilers fall back to the standard guarantee term, so it is worth checking.
Is a Worcester boiler better than a Vaillant?
Both brands sit at the top of the UK market and offer comparable guarantees, efficiency ratings and installer networks. Worcester Bosch has a larger share of UK installations and a very wide spares network; Vaillant uses stainless steel heat exchangers on its ecoTEC ranges and often wins on modulation and quiet running. In practice the quality of the installation and the installer's familiarity with the brand matter more than the badge.
Sources and further reading
- Worcester Bosch - Boilers
- Worcester Bosch - Greenstar 4000
- Worcester Bosch - Greenstar 8000 Life regular
- Worcester Bosch - Our history
- Worcester Bosch - Support and fault codes
- Gas Safe Register - Find a registered engineer
Prices and scheme details were checked on 22 October 2026 and are shown as typical ranges. Always get written quotes from Gas Safe registered installers.